ASTM C1048-18

Standard Specification for Heat-Strengthened and Fully Tempered Flat Glass

ABSTRACT
This specification covers heat-treated flat glass - kind HS, kind FT coated and uncoated glass used in general building construction. Glass furnished under this specification shall be of the following conditions: condition A - uncoated surfaces, condition B - spandrel glass, one surface ceramic coated, and condition C - other coated glass. Flat glass furnished under this specification shall be of the following kinds: kind HS - heat-strengthened glass shall be flat glass, either transparent or patterned, in accordance with the applicable requirements, and kind FT - fully tempered glass shall be flat glass, either transparent or patterned in accordance with the applicable requirements. All fabrication, such as cutting to overall dimensions, edgework, drilled holes, notching, grinding, sandblasting, and etching, shall be performed before strengthening or tempering and shall be as specified. Requirements for fittings and hardware shall be as specified. In heat-strengthened and fully tempered glass, a strain pattern, which is not normally visible, may become visible under certain light conditions. The support system and the amount of glass deflection for a given set of wind-load conditions must be considered for design purposes. Heat-treated flat glass cannot be cut after tempering. Heat-treated glass can be furnished with holes, notches, cutouts, and bevels. The expansion fit and porosity of the ceramic coating shall be tested to meet the requirements prescribed. Specimens for evaluation of resistance to alkali and acid shall be prepared and tested to meet the requirements prescribed.
SCOPE
1.1 This specification covers the requirements for monolithic flat heat-strengthened and fully tempered coated and uncoated glass produced on a horizontal tempering system used in general building construction and other applications.  
1.2 This specification does not address bent glass, or heat-strengthened or fully tempered glass manufactured on a vertical tempering system.  
1.3 The dimensional values stated in SI units are to be regarded as the standard. The units given in parentheses are for information only.  
1.4 The following safety hazards caveat pertains only to the test method portion, Section 10, of this specification:  This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 30-Sep-2018
• ICS: 81.040.30 - Glass products
• Technical Committee: C14 - Glass and Glass Products
• Drafting Committee: C14.08 - Flat Glass

Relations

• Replaces: ASTM C1048-12e1 - Standard Specification for Heat-Strengthened and Fully Tempered Flat Glass
• Effective Date: 01-Oct-2018
• Refers: ASTM E1300-24 - Standard Practice for Determining Load Resistance of Glass in Buildings
• Effective Date: 01-Mar-2024
• Refers: ASTM C1279-23 - Standard Test Method for Non-Destructive Photoelastic Measurement of Edge and Surface Stresses in Annealed, Heat-Strengthened, and Fully Tempered Flat Glass
• Effective Date: 01-Nov-2023
• Refers: ASTM C162-23 - Standard Terminology of Glass and Glass Products
• Effective Date: 01-Oct-2023
• Refers: ASTM C724-91(2020) - Standard Test Method for Acid Resistance of Ceramic Decorations on Architectural-Type Glass
• Effective Date: 01-Aug-2020
• Refers: ASTM C1203-04(2019) - Standard Test Method for Quantitative Determination of Alkali Resistance of a Ceramic-Glass Enamel
• Effective Date: 01-Feb-2019
• Refers: ASTM C978-04(2019) - Standard Test Method for Photoelastic Determination of Residual Stress in a Transparent Glass Matrix Using a Polarizing Microscope and Optical Retardation Compensation Procedures
• Effective Date: 01-Feb-2019
• Refers: ASTM C162-05(2015) - Standard Terminology of<brk type="line"/> Glass and Glass Products
• Effective Date: 01-Nov-2015
• Refers: ASTM C724-91(2015) - Standard Test Method for Acid Resistance of Ceramic Decorations on Architectural-Type Glass
• Effective Date: 01-May-2015
• Refers: ASTM C1203-04(2014) - Standard Test Method for Quantitative Determination of Alkali Resistance of a Ceramic-Glass Enamel
• Effective Date: 01-May-2014
• Refers: ASTM C346-87(2014) - Standard Test Method for 45-deg Specular Gloss of Ceramic Materials
• Effective Date: 01-May-2014
• Refers: ASTM C978-04(2014) - Standard Test Method for Photoelastic Determination of Residual Stress in a Transparent Glass Matrix Using a Polarizing Microscope and Optical Retardation Compensation Procedures
• Effective Date: 01-May-2014
• Refers: ASTM C1279-13 - Standard Test Method for Non-Destructive Photoelastic Measurement of Edge and Surface Stresses in Annealed, Heat-Strengthened, and Fully Tempered Flat Glass
• Effective Date: 01-Oct-2013
• Refers: ASTM E1300-12ae1 - Standard Practice for Determining Load Resistance of Glass in Buildings
• Effective Date: 01-May-2012
• Refers: ASTM E1300-12a - Standard Practice for Determining Load Resistance of Glass in Buildings
• Effective Date: 01-May-2012

Overview

ASTM C1048-18 outlines the standard specification for heat-strengthened and fully tempered flat glass. This glass is widely used in general building construction and related applications. The standard applies specifically to monolithic flat glass-coated or uncoated-produced on a horizontal tempering system. It does not apply to bent glass or glass produced through vertical tempering processes.

ASTM C1048-18 specifies requirements for two kinds of glass:

• Kind HS (Heat-Strengthened Glass): Offers increased resistance to wind pressure and thermal stress compared to annealed glass, but does not meet safety glazing criteria.
• Kind FT (Fully Tempered Glass): Provides significantly higher strength and qualifies as a safety glazing material because it fractures into small, less dangerous pieces upon breakage.

The specification covers fabrication standards, dimensional tolerances, surface quality, coatings, and performance requirements, ensuring glass products meet rigorous safety and quality expectations in the construction industry.

Key Topics

• Glass Types and Conditions:
  • Kind HS (Heat-Strengthened) and Kind FT (Fully Tempered) options.
  • Surface conditions: A) Uncoated, B) Ceramic coated (spandrel glass), C) Other coatings (such as those improving solar control).
• Fabrication Restrictions:
  • All cutting, notching, drilling, or edgework must be performed prior to the heat-treatment process, as post-tempering modifications can compromise glass integrity.
• Design Considerations:
  • Strain patterns and distortion are inherent to heat-treated glass and may become visible under specific lighting.
  • Wind load and glass deflection must be considered in system design, referencing glass thickness and support structure compatibility.
• Testing and Quality:
  • Requirements for surface and edge compression ensure appropriate strength.
  • Tests for coating durability (resistance to acid/alkali, porosity) are included.
  • Fallout resistance for spandrel glass to retain fragments after breakage can be specified.

Applications

Heat-strengthened and fully tempered flat glass manufactured to ASTM C1048-18 is essential for safe and robust architectural glazing. Typical applications include:

• Exterior Windows and Curtain Walls: Provides enhanced strength for larger spans and better performance against wind loads and temperature variations.
• Doors, Shower Enclosures, and Partitions: Fully tempered glass meets safety glazing requirements, making it suitable for areas with a high risk of human impact.
• Spandrel Glass: Ceramic-coated spandrel panels can conceal structural elements while providing color uniformity and durability.
• Furniture, Countertops, and Showcases: Fully tempered glass is ideal for fixtures requiring both transparency and high break resistance.
• Specialty Applications: Includes glass for refrigeration cases, food service equipment, and areas requiring custom shapes, holes, or notches.

Related Standards

When specifying or evaluating products to ASTM C1048-18, the following related standards may also be relevant for comprehensive compliance and optimal performance:

• ASTM C1036: General specification for flat glass, providing baseline requirements for substrate glass.
• ASTM C162: Standard terminology for glass and glass products.
• ASTM C1376: Specification for pyrolytic and vacuum deposition coatings on flat glass.
• ASTM E1300: Practice for determining load resistance of glass in buildings.
• ANSI Z97.1: Safety performance specifications for glazing materials used in buildings.
• CPSC 16 CFR 1201: Federal safety standard for architectural glazing materials.
• GANA 01-0116: Proper procedures for cleaning architectural glass products.

Practical Value

ASTM C1048-18 is the definitive standard for procuring, specifying, and fabricating heat-strengthened and fully tempered flat glass in construction and other industries. Following this standard helps ensure:

• Regulatory and code compliance for safety glazing.
• Consistent quality and predictable performance.
• Durability against weather, thermal, and mechanical stress.
• Compatibility with advanced coatings and fabrication needs.
• Improved occupant safety and minimized property risk in case of glass breakage.

By referencing ASTM C1048-18 and related standards, architects, engineers, fabricators, and contractors can confidently deliver resilient glass solutions that meet modern performance and safety demands.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation:C1048 −18
Standard Specification for
Heat-Strengthened and Fully Tempered Flat Glass
This standard is issued under the fixed designation C1048; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope C724Test Method for Acid Resistance of Ceramic Decora-
tions on Architectural-Type Glass
1.1 This specification covers the requirements for mono-
C978Test Method for Photoelastic Determination of Re-
lithic flat heat-strengthened and fully tempered coated and
sidual Stress in a Transparent Glass Matrix Using a
uncoated glass produced on a horizontal tempering system
Polarizing Microscope and Optical Retardation Compen-
used in general building construction and other applications.
sation Procedures
1.2 This specification does not address bent glass, or heat-
C1036Specification for Flat Glass
strengthened or fully tempered glass manufactured on a verti-
C1203TestMethodforQuantitativeDeterminationofAlkali
cal tempering system.
Resistance of a Ceramic-Glass Enamel
C1279Test Method for Non-Destructive Photoelastic Mea-
1.3 The dimensional values stated in SI units are to be
regardedasthestandard.Theunitsgiveninparenthesesarefor surement of Edge and Surface Stresses in Annealed,
Heat-Strengthened, and Fully Tempered Flat Glass
information only.
C1376Specification for Pyrolytic and Vacuum Deposition
1.4 The following safety hazards caveat pertains only to the
Coatings on Flat Glass
test method portion, Section 10, of this specification: This
E1300PracticeforDeterminingLoadResistanceofGlassin
standard does not purport to address all of the safety concerns,
Buildings
if any, associated with its use. It is the responsibility of the user
2.2 ANSI Standard:
of this standard to establish appropriate safety, health, and
Z97.1Safety Performance Specifications and Methods of
environmental practices and determine the applicability of
Test for Safety Glazing Materials Used in Buildings
regulatory limitations prior to use.
2.3 Other Documents:
1.5 This international standard was developed in accor-
CPSC 16 CFR 1201 Safety Standard for Architectural
dance with internationally recognized principles on standard-
Glazing Materials
ization established in the Decision on Principles for the
GANA 01-0116Proper Procedures for Cleaning Architec-
Development of International Standards, Guides and Recom-
tural Glass Products
mendations issued by the World Trade Organization Technical
Barriers to Trade (TBT) Committee.
3. Terminology
3.1 Definitions—For definitions of terms used in this
2. Referenced Documents
specification, refer to Terminology C162 and Specification
2,3
2.1 ASTM Standards:
C1036.
C162Terminology of Glass and Glass Products
3.2 Definitions of Terms Specific to This Standard:
C346Test Method for 45-deg Specular Gloss of Ceramic
3.2.1 bow—the deviation in flatness of a lite of glass,
Materials
expressed over the entire width or length dimension of the
glass or over a smaller, local area (see 10.7 for measurement
This specification is under the jurisdiction ofASTM Committee C14 on Glass technique).
and Glass Products and is the direct responsibility of Subcommittee C14.08 on Flat
3.2.2 coating voids, condition B—uncoated areas forming
Glass.
unintentional discernable irregularities in the intended flood
Current edition approved Oct. 1, 2018. Published November 2018. Originally
ε1
approved in 1985. Last previous edition approved in 2012 as C1048–12a . DOI:
coat, pattern, or image.
10.1520/C1048-18.
Reference to these documents shall be the latest issue unless otherwise
specified by the authority applying this specification. Available from American National Standards Institute, 25 W. 43rd St., 4th
For referenced ASTM standards, visit the ASTM website, www.astm.org, or Floor, NewYork, NY10036, and theAccredited Standards Committee Z97 website
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM in electronic format at www.ansiz97.com.
Standards volume information, refer to the standard’s Document Summary page on Available from Superintendent of Documents, U.S. Government Printing
the ASTM website. Office, Washington, DC 20402.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
C1048−18
3.2.3 edge curl (also edge lift, edge kink)—an out-of-plane pattern of fully tempered glass is not required. When broken,
deformation near the physical leading and/or trailing edges of heat-strengthened glass fragments are more similar in size and
flat glass processed in a horizontal roller hearth furnace, shape to annealed glass fragments than to fully tempered glass
observed as being concave or convex in nature. particles, and thus tend to stay in the opening longer than fully
tempered glass particles.
3.2.4 heat-treated glass—a term used to reference both
heat-strengthened and fully tempered glass.
NOTE 1—Caution: Monolithic heat-strengthened glass is not suitable
for safety glazing as defined by ANSI Z97.1 or CPSC 16 CFR 1201.
3.2.5 heat-treating—the process of heating and cooling
annealed glass in a tempering system to produce either 5.2 Kind FT—Fully tempered glass is used in architectural
heat-strengthened or fully tempered glass. glazing applications when significant additional strength is
needed to resist wind pressure, a mechanical load and/or
3.2.6 opaque particle—undispersed debris trapped in the
thermal stress. When broken, fully tempered glass fractures
coated surface.
(dices) into relatively small particles. Fully tempered glass
3.2.7 relief cut—the removal of a narrow section of glass-
withsufficientsurfacecompressiontomeettherequirementsof
fromtheglassedgetotherimofaglassholeintendedtoreduce
safety glazing standard such as CPSC 16, CFR 1201, orANSI
breakage and stress concentrations during the fabrication and
Z97.1 is considered a safety glass because it fractures into
heat-treating process.
relatively small pieces thereby greatly reducing the likelihood
3.2.8 scattered pinholes—small light transmitting voids in
ofseriouscuttingorpiercinginjuriesincomparisontoordinary
applied ceramic frit coatings, requiring backlighting for vis-
annealed glass. For some applications, such as doors used for
ibility.
passage, tub and shower enclosures and fixed glass in close
proximity to a walking surface, fully tempered safety glass is
3.2.9 screen mark (mesh mark)—a mesh pattern left by a
silk screen process in the applied ceramic glass enamel before required by building codes and ordinances. Fully tempered
safety glass is often used for other applications where its
or after firing.
strength or safety characteristics, or both, are desirable such as
3.2.10 thermal stress—stress caused by thermal gradients
table tops, counter tops, show case enclosures, refrigeration
across the glass surface.
andfoodserviceequipment,furniture,andsimilarapplications.
4. Classification
6. Ordering Information
4.1 Kinds—Flat glass furnished under this specification
6.1 Purchasersshouldselectthepreferredoptionspermitted
shall be of the following kinds, as specified (see Section 6):
in this specification and include the following information in
4.1.1 Kind HS—Heat-strengthened glass shall be flat glass,
procurement documents:
either transparent or patterned, in accordance with the appli-
6.1.1 Number, date, and title of this specification.
cablerequirementsofSpecificationC1036asfurtherprocessed
6.1.2 Kind,condition,type,class,style,form,quality,finish,
to conform with the requirements hereinafter specified for
and pattern of glass as applicable (see Section 4).
heat-strengthened glass.
6.1.3 Fabrication requirements (see 7.7).
4.1.2 Kind FT—Fully tempered glass shall be flat glass,
6.1.4 Requirements for fittings and hardware (see 7.1).
either transparent or patterned in accordance with the appli-
6.1.5 Glass thickness (see 9.1).
cablerequirementsofSpecificationC1036asfurtherprocessed
6.1.6 Non-rectangular shapes must be within the tolerances
toconformwiththerequirementshereinafterspecifiedforfully
specified (see 9.3).
tempered glass.
6.1.7 When surface or edge compression test is required for
4.2 Conditions—Glass furnished under this specification
heat–strengthened or fully tempered glass (see 8.1.1).
shall be of the following conditions, as specified (see Section
6.1.8 When break safe characteristics are required for fully
6):
tempered glass (see 8.1.2).
4.2.1 Condition A—Uncoated surfaces.
6.1.9 Color or tint of glass (see 8.2).
4.2.2 Condition B—Fully or partially ceramic coated glass
6.1.10 When either permanent or temporary identification
havingaceramiccoatingofaspecifiedcolor,pattern,orimage
marking is required (see Section 11).
which has been fused onto and made an integral part of the
6.1.11 Coatings, color, pattern, percent coverage, or image
surface of the glass as a result of the heat treating process.
for Condition B and Condition C glass (see 8.3 and 8.4).
4.2.3 Condition C—Other coated glass with a pyrolytic or
6.1.12 When addition of fallout resistance capability is
vacuum deposition coating typically applied to affect charac-
required for ConditionA, Condition B, or Condition C glasses
teristics such as solar heat gain, energy performance, comfort
used as spandrels. (Normally achieved by adhering a reinforc-
level, condensation, and the aesthetics of the building.
ing material to the glass surface.) (See 10.3.)
4.3 Types, Classes, Forms, Qualities, and Finishes—these
are described in Specification C1036.
7. Properties and Fabrication of Heat-Treated Glass
NOTE 2—The stress distribution and fracture characteristics of heat-
5. Intended Use treated glass result in some unique properties and fabrication consider-
ationsforheat-strengthenedandfullytemperedglass.Theinformationand
5.1 Kind HS—Heat-strengthened glass is used as architec-
guidelinesinthissectionaremeanttoprovideunderstandingandguidance
tural glazing when additional resistance to wind pressure
toheat-treatedglassusersincluding,butnotlimitedto,architects,owners,
and/orthermalstressisdesired,butthestrengthorsafetybreak specifiers, consultants, and contractors.
C1048−18
7.1 Distortion: tooneorbothglasssurfaces.Thesesurfaceparticlesmayoccur
fromavarietyofsourcesincluding,butnotlimitedto,theglass
7.1.1 Heat-strengthened and fully tempered glass is made
cutting and edging process, typical manufacturing plant air-
by heating annealed glass in a tempering system to a tempera-
bornedebrisordust,refractoryparticlesfromthefurnaceroof,
ture at which the glass becomes slightly plastic. Immediately
and external airborne dirt and grit carried into the plant by the
after heating, the glass surfaces are rapidly cooled by quench-
large volumes of quench air used in the process. Particles on
ing with air. The original flatness of the glass is slightly
thefurnacerollersmaybepickedupbythehotbottomsurface
modified by the process, causing reflected images to be
of the glass as it travels over the particles. Surface particles
distorted. When viewing images through the glass, the
invisible to the naked eye are inherent in the heat-treating
distortion, in most glazing applications, is less than that of
process and are not a cause for rejection.
reflected images.
7.1.2 Heat-strengthened and fully tempered glass that has
7.5 Glass Cleaning—Scrapers and/or razor blades shall not
been produced in a horizontal tempering system may contain
beusedaspartofaroutineglasscleaningprocessbecausesuch
surfacedistortion(forexample,pictureframing,heatdistortion
use may result in scratches from dragging surface particles
or roller wave distortion). Distortion may be detected when
across the glass surface. In some cases the resulting scratches
viewing images in reflection or transmission and may be more
may only be visible under certain lighting conditions. It is
noticeable at viewing angles other than perpendicular.
important to use proper cleaning procedures when cleaning
7.1.3 Pressures exerted around the periphery of glass by the architectural glass products to avoid causing scratches; see
glazing system can also alter glass flatness, thereby distorting
GANA/IWCA01-0116 Proper Procedures for CleaningArchi-
reflected images.This is true regardless of whether the glass is tectural Glass Products.
annealed, heat-strengthened, or fully tempered.
7.6 Resistance to Wind Load—The structural performance
7.1.4 Sealed insulating glass units also exhibit distortion
and load-induced deflections of the glass under uniform load
regardless of glass type. Air or other gas, sealed in the gap
conditions shall be properly considered in relationship to the
between the lites of glass, expands or contracts with tempera-
requirements of the application, and consistent with Practice
ture and barometric changes, creating a pressure differential
E1300 as applicable.
betweenthesealedgapandtheatmosphere.Theglassreactsto
7.7 Fabrication—Heat-strengthened and fully tempered
the pressure differential by being deflected inward or outward.
glasscanbefurnishedwithholes,notches,cutouts,andbevels.
7.1.5 Regardless of glass flatness, the degree of reflected
Fabrication involving other methods of modification shall be
distortion perceived is largely due to the characteristics or
discussed with the fabricator/manufacturer.
symmetryoftheobjectbeingreflected.Linearobjects(suchas
7.7.1 Fabrication Guidelines—Heat-strengthened and fully
buildingcurtainwallsandtelephonepoles)andmovingobjects
temperedflatglasscannotbecutaftertheheat-treatingprocess.
(such as cars) may appear distorted. Irregular and free-form
Fabrication altering the glass surface, thickness, or edges shall
objects such as trees and clouds may appear to have less
be performed before heat-treating to avoid a reduction of glass
perceived distortion.
strength.
7.1.6 Specified bow limits may not adequately define, or
7.7.2 Fittings and Hardware—Requirementsforfittingsand
control, the distortion that may become apparent after glazing.
hardware shall be as specified (see Section 6) or as shown on
The factors, noted above, may have a larger influence on the
plans or drawings. Fittings and hardware specified shall be
perceivedreflecteddistortionthanthatwhichiscausedbybow
compatible with glass fabrication guidelines.
fromtheheat-treatingprocess.Consultationwithsuppliersand
7.7.3 Placement of Holes:
theviewingoffull-sizemock-ups,undertypicaljobconditions
7.7.3.1 Theminimumdistancefromanyedgeoftheglassto
and surroundings, is highly recommended for evaluation of
the nearest point on the rim of a hole shall be 6 mm ( ⁄4 in.) or
reflective distortion.
two times the thickness of the glass, whichever is greater (see
Fig. 1).
7.2 Strain Pattern—A strain pattern, also known as
7.7.3.2 The minimum distance between the rims of adjoin-
iridescence, is inherent in all heat-strengthened and fully
ing holes shall be 10 mm ( ⁄8 in.) or two times the thickness of
tempered glass. This strain pattern may become visible under
glass, whichever is greater (see Fig. 1).
certain polarized lighting conditions. It is a characteristic of
7.7.3.3 Holes near corners shall be located so that the
heat-treated glass and should not be mistaken as discoloration,
nearest edge of the hole is a minimum of 6.5 times the
non-uniform tint or color, or a defect in the glass. The strain
thicknessoftheglassfromthetipofthecornerwhenthecorner
pattern does not affect any physical properties or performance
is 90° or more (see Fig. 2). When the corner is less than 90 or
values of the glass.
rounded, the minimum distance between the hole and the edge
7.3 Edge Curl (also edge lift, edge kink)—Glass which is
shallbemaintainedatminimum6mm( ⁄4in.)ortwotimesthe
heat treated in a horizontal furnace may show some level of
glassthickness,whicheverisgreater.Alsomayrequirethehole
edge curl.
be located asymmetric with respect to the corner.
7.4 Surface Particles—The production of heat-strengthened 7.7.3.4 If a hole is placed closer to the edge than
and fully tempered glass involves the transport of very hot recommended, the risk of glass breakage increases substan-
glassonconveyorrollers.Asaresultofthissoftglass-to-roller tially.Thismaybereducedbymakingareliefcutfromtherim
contact, some glass surface changes will occur. Minute par- oftheholetothenearestedgepriortotheheattreatingprocess.
ticles (fines), typically invisible to the naked eye, may adhere Consult the glass fabricator and hardware supplier.
C1048−18
X=6mm( ⁄4 in.) or 2t, whichever is greater
Y = 10 mm ( ⁄8 in.) or 2t, whichever is greater
D=6mm(1/4in.)or1t,whichever is greater
where: R$ t
X = Minimum distance between glass edge and rim of nearest hole,
Y = Minimum distance between rims of adjoining holes, and where:
t = Glass thickness. D = Minimum diameter of a hole,
R = Radius, and
t = Glass thickness.
FIG. 1Location of Holes Near Edge
FIG. 3Minimum Dimension of Holes
7.7.5.3 Tolerance for dimension between hole centers shall
be 61.6 mm ( ⁄16in.).
7.7.6 Chips and flakes at hole edges shall not exceed
3.2mm ( ⁄8in.). Exception: chips and flakes at countersunk
holes shall not exceed 0.8mm ( ⁄32in.).
7.7.7 Notches and Cutouts:
7.7.7.1 Notches and cutouts shall have fillets, the radius of
whichshallbeequaltoorgreaterthanthethicknessoftheglass
(see Fig. 4).
R$ t
where:
X=6.5*t
t = thickness of glass, and
Z=6mm( ⁄4 in.) or 2 * t, whichever is greater
R = radius.
where:
FIG. 4Notch and Cutout Fillets
X = Minimum distance between glass corner and rim of nearest hole,
Z = Minimum distance between rim and hole and rounded corner, and
t = Glass thickness.
7.7.7.2 Dimensional tolerance of notches and cutouts shall
FIG. 2Location of Holes Near Corners
be:
1 1
±1.6mm( ⁄16 in.) for glass thickness less than 12 mm ( ⁄2 in.)
1 1
±3 mm ( ⁄8 in.) for glass thickness of 12 mm ( ⁄2 in.) and greater
.
7.7.7.3 Inner surfaces of notches and cutouts shall be
7.7.4 Minimum Dimension of Holes—Circular holes shall
have a minimum diameter of 6 mm ( ⁄4in.) or the thickness of smooth, seamed, ground, or polished.
7.7.8 Consult manufacturer regarding heat-treatment of
theglass,whicheverisgreater.Inotherthancircularholes,any
corners shall have fillets, the radius of which shall be equal to glass with irregular patterns, surface treatments, unusual edge
work or any fabrication that falls outside these guidelines.
or greater than the thickness of the glass (see Fig. 3).
7.7.5 Dimensional Tolerances of Holes:
8. Other Requirements
7.7.5.1 Tolerance of hole diameter shall be 61.6 mm
( ⁄16in.). 8.1 Strength Requirements:
7.7.5.2 Tolerance for dimensions of hole center from speci- 8.1.1 Surface and Edge Compression Requirements (see
fied edges shall be 61.6 mm ( ⁄16 in.). 10.8):
C1048−18
8.1.1.1 Kind HS, Heat-Strengthened Glass—Kind HS glass teristics such as solar heat gain, energy performance, comfort
with thicknesses of 6 mm ( ⁄4 in.) and less shall have a surface level, condensation, and the aesthetics of the building (see
compression between 24 to 52 MPa (3500 and 7500 psi). Specification C1376).
Surface compression testing, when required (see 6.1.7), shall
9. Dimension Requirements
be done in accordance with 10.8.
9.1 Thickness—Substrates for heat-strengthened and fully
NOTE 3—Heat-strengthening of glass thicker than 6 mm ( ⁄4 in.) can be
d
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
´1
Designation: C1048 − 12 C1048 − 18
Standard Specification for
Heat-Strengthened and Fully Tempered Flat Glass
This standard is issued under the fixed designation C1048; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the U.S. Department of Defense.
ε NOTE—Section 9 was updated editorially in November 2012.
1. Scope
1.1 This specification covers the requirements for monolithic flat heat-strengthened and fully tempered coated and uncoated
glass produced on a horizontal tempering system used in general building construction and other applications.
1.2 This specification does not address bent glass, or heat-strengthened or fully tempered glass manufactured on a vertical
tempering system.
1.3 The dimensional values stated in SI units are to be regarded as the standard. The units given in parentheses are for
information only.
1.4 The following safety hazards caveat pertains only to the test method portion, Section 10, of this specification: This standard
does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this
standard to establish appropriate safety safety, health, and healthenvironmental practices and determine the applicability of
regulatory limitations prior to use.
1.5 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2 ,3
2.1 ASTM Standards: ,
C162 Terminology of Glass and Glass Products
C346 Test Method for 45-deg Specular Gloss of Ceramic Materials
C724 Test Method for Acid Resistance of Ceramic Decorations on Architectural-Type Glass
C978 Test Method for Photoelastic Determination of Residual Stress in a Transparent Glass Matrix Using a Polarizing
Microscope and Optical Retardation Compensation Procedures
C1036 Specification for Flat Glass
C1203 Test Method for Quantitative Determination of Alkali Resistance of a Ceramic-Glass Enamel
C1279 Test Method for Non-Destructive Photoelastic Measurement of Edge and Surface Stresses in Annealed, Heat-
Strengthened, and Fully Tempered Flat Glass
C1376 Specification for Pyrolytic and Vacuum Deposition Coatings on Flat Glass
E1300 Practice for Determining Load Resistance of Glass in Buildings
2.2 ANSI Standard:
Z97.1 Safety Performance Specifications and Methods of Test for Safety Glazing Materials Used in Buildings
2.3 Other Documents:
CPSC 16 CFR 1201 Safety Standard for Architectural Glazing Materials
GANA 01-0116 Proper Procedures for Cleaning Architectural Glass Products
This specification is under the jurisdiction of ASTM Committee C14 on Glass and Glass Products and is the direct responsibility of Subcommittee C14.08 on Flat Glass.
Current edition approved March 15, 2012Oct. 1, 2018. Published May 2012November 2018. Originally approved in 1985. Last previous edition approved in 20042012
ε1
as C1048 – 04.C1048 – 12a . DOI: 10.1520/C1048-12E01.10.1520/C1048-18.
Reference to these documents shall be the latest issue unless otherwise specified by the authority applying this specification.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Available from American National Standards Institute, 25 W. 43rd St., 4th Floor, New York, NY 10036, and the Accredited Standards Committee Z97 website in electronic
format at www.ansiz97.com.
Available from Superintendent of Documents, U.S. Government Printing Office, Washington, DC 20402.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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3. Terminology
3.1 Definitions—For definitions of terms used in this specification, refer to Terminology C162 and Specification C1036.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 bow, bow—n—the deviation in flatness of a lite of glass, expressed over the entire width or length dimension of the glass
or over a smaller, local area (see 10.7 for measurement technique). Also known as warp.
3.2.2 coating voids, condition B—uncoated areas forming unintentional discernable irregularities in the intended flood coat,
pattern, or image.
3.2.3 edge curl (also edge lift, edge kink)—an out-of-plane deformation near the physical leading and/or trailing edges of flat
glass processed in a horizontal roller hearth furnace, observed as being concave or convex in nature.
3.2.4 heat-treated glass, glass—n—a term used to reference both heat-strengthened and fully tempered glass.
3.2.5 heat-treating, heat-treating—v—the process of heating and cooling annealed glass in a tempering system to produce either
heat-strengthened or fully tempered glass.
3.2.6 opaque particle—undispersed debris trapped in the coated surface.
3.2.7 relief cut—the removal of a narrow section of glassfrom the glass edge to the rim of a glass hole intended to reduce
breakage and stress concentrations during the fabrication and heat-treating process.
3.2.8 scattered pinholes—small light transmitting voids in applied ceramic frit coatings, requiring backlighting for visibility.
3.2.9 screen mark (mesh mark)—a mesh pattern left by a silk screen process in the applied ceramic glass enamel before or after
firing.
3.2.10 thermal stress, stress—n—edge stress caused by thermal gradients across the glass surface.
4. Classification
4.1 Kinds—Flat glass furnished under this specification shall be of the following kinds, as specified (see Section 6):
4.1.1 Kind HS—Heat-strengthened glass shall be flat glass, either transparent or patterned, in accordance with the applicable
requirements of Specification C1036 as further processed to conform with the requirements hereinafter specified for heat-
strengthened glass.
4.1.2 Kind FT—Fully tempered glass shall be flat glass, either transparent or patterned in accordance with the applicable
requirements of Specification C1036 as further processed to conform with the requirements hereinafter specified for fully tempered
glass.
4.2 Conditions—Glass furnished under this specification shall be of the following conditions, as specified (see Section 6):
4.2.1 Condition A—Uncoated surfaces.
4.2.2 Condition B—Fully or partially ceramic coated glass. (Seeglass having 8.3.)a ceramic coating of a specified color, pattern,
or image which has been fused onto and made an integral part of the surface of the glass as a result of the heat treating process.
4.2.3 Condition C—Other coated glass. (Seeglass with 8.4.)a pyrolytic or vacuum deposition coating typically applied to affect
characteristics such as solar heat gain, energy performance, comfort level, condensation, and the aesthetics of the building.
4.3 Types, Classes, Forms, Qualities, and Finishes—these are described in Specification C1036.
5. Intended Use
5.1 Kind HS—Heat-strengthened glass is used as architectural glazing when additional resistance to wind pressure or thermal
stress, or both, and/or thermal stress is desired, but the strength or safety break pattern of fully tempered glass is not required. When
broken, heat-strengthened glass fragments are more similar in size and shape to annealed glass fragments than to fully tempered
glass particles, and thus tend to stay in the opening longer than fully tempered glass particles.
NOTE 1—Caution: Monolithic heat-strengthened glass is not suitable for safety glazing as defined by ANSI Z97.1 or CPSC 16 CFR 1201.
5.2 Kind FT—Fully tempered glass is used in architectural glazing applications when significant additional strength is needed
to resist wind pressure or thermal stress, or both. pressure, a mechanical load and/or thermal stress. When broken, fully tempered
glass fractures (dices) into relatively small particles. Fully tempered glass with sufficient surface compression to meet the
requirements of safety glazing standard such as CPSC 16, CFR 1201, or ANSI Z97.1, or both, Z97.1 is considered a safety glass
because it fractures into relatively small pieces thereby greatly reducing the likelihood of serious cutting or piercing injuries in
comparison to ordinary annealed glass. For some applications, such as doors used for passage, tub and shower enclosures and fixed
glass in close proximity to a walking surface, fully tempered safety glass is required by building codes and ordinances. Fully
tempered safety glass is often used for other applications where its strength or safety characteristics, or both, are desirable such
as table tops, counter tops, show case enclosures, refrigeration and food service equipment, furniture, and similar applications.
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6. Ordering Information
6.1 Purchasers should select the preferred options permitted in this specification and include the following information in
procurement documents:
6.1.1 Number, date, and title of this specification.
6.1.2 Kind, condition, type, class, style, form, quality, finish, and pattern of glass as applicable (see Section 4).
6.1.3 Fabrication requirements (see 7.17.7).
6.1.4 Requirements for fittings and hardware (see 7.27.1).
6.1.5 Custom design or texture required (see 7.7).
6.1.5 Glass thickness (see 9.1).
6.1.6 Pattern-cut glassNon-rectangular shapes must be within the tolerances specified (see 9.3).
6.1.7 When surface or edge compression test is required for heat–strengthened or fully tempered glass (see 8.1.1).
6.1.8 When break safe characteristics are required for fully tempered glass (see 8.1.2).
6.1.9 Color or tint of glass (see 8.2).
6.1.10 When either permanent or temporary identification marking is required (see Section 11).
6.1.11 Surface treatment or coatingsCoatings, color, pattern, percent coverage, or image for Condition B and Condition C glass
(see 8.3 and 8.4).
6.1.12 When addition of fallout resistance capability is required for Condition A, Condition B, or Condition C glasses used as
spandrels. (Normally achieved by adhering a reinforcing material to the glass surface.) (See 10.3.)
7. Fabrication Properties and Fabrication of Heat-Treated Glass
7.1 Fabrication—All fabrication, such as cutting to overall dimensions, edgework, drilled holes, notching, grinding,
sandblasting, and etching, shall be performed before heat-strengthening or tempering and shall be as specified (see Section 6 and
7.8). After the glass has been heat-strengthened or tempered, it shall not be modified except as recommended by the fabricator;
for example, some Condition C coatings. No modification shall be made that will affect its structural characteristics or integrity
as specified in this standard.
NOTE 2—The stress distribution and fracture characteristics of heat-treated glass result in some unique properties and fabrication considerations for
heat-strengthened and fully tempered glass. The information and guidelines in this section are meant to provide understanding and guidance to heat-treated
glass users including, but not limited to, architects, owners, specifiers, consultants, and contractors.
7.2 Fittings and Hardware—Requirements for fittings and hardware shall be as specified (see Section 6) or as shown on plans
or drawings. Fittings and hardware specified shall be compatible with glass fabrication limitations.
7.1 Distortion:
7.1.1 Heat-strengthened and fully tempered glass is made by heating annealed glass in a tempering system to a temperature at
which the glass becomes slightly plastic. Immediately after heating, the glass surfaces are rapidly cooled by quenching with air.
The original flatness of the glass is slightly modified by the process, causing reflected images to be distorted. When viewing images
through the glass, the distortion, in most glazing applications, is less than that of reflected images.
7.1.2 Heat-strengthened and fully tempered glass that has been produced in a horizontal tempering system may contain surface
distortion (for example, picture framing, heat distortion or roller wave distortion). Distortion may be detected when viewing images
reflected from the glass surface.in reflection or transmission and may be more noticeable at viewing angles other than
perpendicular.
7.1.3 Pressures exerted around the periphery of glass by the glazing system can also alter glass flatness, thereby distorting
reflected images. This is true regardless of whether the glass is annealed, heat-strengthened, or fully tempered.
7.1.4 Sealed insulating glass units also exhibit distortion regardless of glass type. Air or other gas, sealed in the gap between
the lites of glass, expands or contracts with temperature and barometric changes, creating a pressure differential between the sealed
gap and the atmosphere. The glass reacts to the pressure differential by being deflected inward or outward.
7.1.5 Regardless of glass flatness, the degree of reflected distortion perceived is largely due to the characteristics or symmetry
of the object being reflected. Linear objects (such as building curtain walls and telephone poles) and moving objects (such as cars)
may appear distorted. Irregular and free-form objects such as trees and clouds may appear to have less perceived distortion.
7.1.6 Specified bow limits may not adequately define, or control, the distortion that may become apparent after glazing. The
factors, noted above, may have a larger influence on the perceived reflected distortion than that which is caused by bow from the
heat-treating process. Consultation with suppliers and the viewing of full-size mock-ups, under typical job conditions and
surroundings, is highly recommended for evaluation of reflective distortion.
7.2 Strain Pattern—A strain pattern, also known as iridescence, is inherent in all heat-strengthened and fully tempered glass.
This strain pattern may become visible under certain polarized lighting and other conditions. It is a characteristic of heat-treated
glass and should not be mistaken as discoloration, non-uniform tint or color, or a defect in the glass. The strain pattern does not
affect any physical properties or performance values of the glass.
7.3 Edge Curl (also edge lift, edge kink)—Glass which is heat treated in a horizontal furnace may show some level of edge curl.
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7.4 Surface Particles—The production of heat-strengthened and fully tempered glass involves the transport of very hot glass on
conveyor rollers. As a result of this soft glass-to-roller contact, some glass surface changes will occur. Minute particles (fines),
typically invisible to the naked eye, may adhere to one or both glass surfaces. These surface particles may occur from a variety
of sources including, but not limited to, the glass cutting and edging process, typical manufacturing plant airborne debris or dust,
refractory particles from the furnace roof, and external airborne dirt and grit carried into the plant by the large volumes of quench
air used in the process. Particles on the furnace rollers may be picked up by the hot bottom surface of the glass as it travels over
the particles. Surface particles invisible to the naked eye are inherent in the heat-treating process and are not a cause for rejection.
7.5 Glass Cleaning—Scrapers and/or razor blades shall not be used as part of a routine glass cleaning process because such use
may result in scratches from dragging surface particles across the glass surface. In some cases the resulting scratches may only
be visible under certain lighting conditions. It is important to use proper cleaning procedures when cleaning architectural glass
products to avoid causing scratches; see GANA/IWCA 01-0116 Proper Procedures for Cleaning Architectural Glass Products.
7.6 Resistance to Wind Load—The support system and the amount of glass deflection for a given set of wind-load structural
performance and load-induced deflections of the glass under uniform load conditions shall be considered for design purposes.
Consult the manufacturer to determine the appropriate thickness of heat-strengthened or fully tempered glass needed to satisfy the
design wind load and probability of breakage design factor for the required glass in accordance properly considered in relationship
to the requirements of the application, and consistent with Practice E1300. as applicable.
7.7 Special Surfaces, Types I or II—Custom designs or textures shall be as specified (see 6.1.5) or as shown on plans or
drawings.
7.7 Fabrication Guidelines—Fabrication—Heat-strengthened and fully tempered flat glass cannot be cut after the heat-treating
process. Fabrication altering the glass surface, thickness, or edges shall be performed before heat-treating to avoid a reduction of
glass strength. can be furnished with holes, notches, cutouts, and bevels. Fabrication involving other methods of modification shall
be discussed with the fabricator/manufacturer.
7.7.1 Fabrication Guidelines—Heat-strengthened and fully tempered flat glass can be furnished with holes, notches, cutouts,
and bevels. Fabrication involving other methods of modification should be discussed with the fabricator/manufacturer.cannot be
cut after the heat-treating process. Fabrication altering the glass surface, thickness, or edges shall be performed before heat-treating
to avoid a reduction of glass strength.
7.7.2 Fittings and Hardware—Requirements for fittings and hardware shall be as specified (see Section 6) or as shown on plans
or drawings. Fittings and hardware specified shall be compatible with glass fabrication guidelines.
7.7.3 Placement of Holes:
7.7.3.1 The minimum distance from any edge of the glass to the nearest point on the rim of a hole shall be 6 mm ( ⁄4 in.) or
2two times the thickness of the glass, whichever is greater (see Fig. 1).
7.7.3.2 The minimum distance between the rims of adjoining holes shall be 10 mm ( ⁄8 in.) or 2two times the thickness of glass,
whichever is greater (see Fig. 1).
7.7.3.3 Holes near corners shall be located so that the nearest edge of the hole is a minimum of 6.5 times the thickness of the
glass from the tip of the corner when the corner is 90° or more (see Fig. 2). When the corner is less than 90 or rounded, the
minimum distance between the hole and the edge shall be maintained at minimum 6 mm ( ⁄4 in.) or two times the glass thickness,
whichever is greater. Also may require the hole be located asymmetric with respect to the corner.
7.7.3.4 If a hole is placed closer to the edge than recommended, the risk of glass breakage increases substantially. This may be
reduced by making a relief cut from the rim of the hole to the nearest edge prior to the heat treating process. Consult the glass
fabricator and hardware supplier.
7.7.4 Minimum Dimension of Holes—Circular holes shall have a minimum diameter of 6 mm ( ⁄4 in.) in.) or the thickness of
the glass, whichever is greater. In other than circular holes, any corners shall have fillets, the radius of which shall be equal to or
greater than the thickness of the glass (see Fig. 3).
7.7.5 Dimensional Tolerances of Holes:
7.7.5.1 Tolerance of hole diameter shall be 61.6 mm ( ⁄16 in.). in.).
7.7.5.2 Tolerance for dimensions of hole center from specified edges shall be 61.6 mm ( ⁄16 in.).
7.7.5.3 Tolerance for dimension between hole centers shall be 61.6 mm ( ⁄16 in.). in.).
7.7.6 Chips and flakes at hole edges shall not exceed 1.6 mm 3.2 mm ( ⁄8 in.). in.). Exception: chips and flakes at countersunk
holes shall not exceed 0.8 mm ( ⁄32 in.).
7.7.7 Notches and Cutouts:
7.7.7.1 Notches and cutouts shall have fillets, the radius of which shall be equal to or greater than the thickness of the glass (see
Fig. 4).
7.7.7.2 Dimensional tolerance of notches and cutouts shall be:
1 1
±1.6 mm ( ⁄16 in.) for glass thickness less than 12 mm ( ⁄2 in.)
1 1
±3 mm ( ⁄8 in.) for glass thickness of 12 mm ( ⁄2 in.) and greater
1 1
6 1.6 mm (. ⁄16 in.) for glass thickness less than 12 mm ( ⁄2 in.).
1 1
6 3 mm ( ⁄8 in.) for glass thickness of 12 mm ( ⁄2 in.) and greater.
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X = 6 mm ( ⁄4 in.) or 2t, whichever is greater
Y = 10 mm ( ⁄8 in.) or 2t, whichever is greater
Where:
X = Minimum distance between glass edge and rim of nearest hole
Y = Minimum distance between rims of adjoining holes
t = Glass thickness
X = 6 mm ( ⁄4 in.) or 2t, whichever is greater
Y = 10 mm ( ⁄8 in.) or 2t, whichever is greater
where:
X = Minimum distance between glass edge and rim of nearest hole,
Y = Minimum distance between rims of adjoining holes, and
t = Glass thickness.
FIG. 1 Placement Location of Holes Near Edge
X = 6.5t
Where:
X = Minimum distance between glass corner and rim of nearest hole
t = Glass thickness
X = 6.5 * t
Z = 6 mm ( ⁄4 in.) or 2 * t, whichever is greater
where:
X = Minimum distance between glass corner and rim of nearest hole,
Z = Minimum distance between rim and hole and rounded corner, and
t = Glass thickness.
FIG. 2 Location of Holes Near Corners
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D = 6 mm (1/4 in.) or 1t, whichever is greater
R ≥ t
Where:
D = Minimum diameter of a hole
R = Radius
t = Glass thickness
D = 6 mm (1/4 in.) or 1t, whichever is greater
R $ t
where:
D = Minimum diameter of a hole,
R = Radius, and
t = Glass thickness.
FIG. 3 Minimum Dimension of Holes
R ≥ t
t = thickness of glass
R = radius
See paragraph 7.8.6.
R $ t
where:
t = thickness of glass, and
R = radius.
FIG. 4 Notch and Cutout Fillets
7.7.7.3 Inner surfaces of notches and cutouts shall be smooth, seamed, ground, or polished.
7.7.8 Consult manufacturer regarding heat-treatment of glass with irregular patterns, surface treatments, unusual edge work or
any fabrication that falls outside these guidelines.
8. Other Requirements
8.1 Strength Requirements:
8.1.1 Surface and Edge Compression Requirements (see 10.8):
8.1.1.1 Kind HS, Heat-Strengthened Glass—Kind HS glass with thicknesses of 6 mm ( ⁄4 in.) and less shall have a surface
compression between 24 to 52 MPa (3500 and 7500 psi). Surface compression testing, when required (see 6.1.86.1.7), shall be
done in accordance with 10.8.
NOTE 3—Heat-strengthening of glass thicker than 6 mm ( ⁄4 in.) can be difficult. Consult manufacturer.the fabricator providing the heat-strengthened
glass.
C1048 − 18
8.1.1.2 Kind FT, Fully Tempered Glass—Fully tempered glass shall have either a minimum surface compression of 69 MPa
69 MPa (10 000 ps
...