ISO 20657:2017
(Main)Glass in building — Heat soaked tempered soda lime silicate safety glass
Glass in building — Heat soaked tempered soda lime silicate safety glass
ISO 20657:2017 specifies product definitions, product characteristics, i.e. tolerances, flatness, edgework, etc., fracture characteristics, including fragmentation, and the physical and mechanical characteristics of flat heat soaked tempered soda lime silicate safety glass for use in buildings. ISO 20657:2017 does not cover curved (bent) glass according ISO 11485.
Verre dans la construction — Verre de sécurité de silicate sodocalcique trempé et traité
General Information
Standards Content (Sample)
INTERNATIONAL ISO
STANDARD 20657
First edition
2017-03
Glass in building — Heat soaked
tempered soda lime silicate safety glass
Verre dans la construction — Verre de sécurité de silicate
sodocalcique trempé et traité
Reference number
©
ISO 2017
© ISO 2017, Published in Switzerland
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ii © ISO 2017 – All rights reserved
Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Glass products . 3
5 Manufacturing processes. 3
5.1 General . 3
5.2 Tempering process . 3
5.3 Heat soak process cycles . 4
5.3.1 Off-line process . 4
5.3.2 In-line process . 7
6 Fracture characteristics . 8
6.1 General . 8
6.2 Accidental human impact . 8
6.3 Fragmentation . 8
7 Dimensions and tolerances . 9
7.1 Nominal thickness and thickness tolerances . 9
7.2 Width and length (sizes) . 9
7.2.1 General. 9
7.2.2 Maximum and minimum sizes .10
7.2.3 Tolerances and squareness .10
7.2.4 Edge deformation produced by vertical tempering .11
7.3 Flatness .11
7.3.1 General.11
7.3.2 Measurement of overall bow .13
7.3.3 Measurement of wave or roller wave distortion .14
7.3.4 Measurement of edge lift (only for heat soaked tempered safety glass
which was horizontally tempered) .15
7.3.5 Measurement of perimeter deformation of glass produced by air cushion
tempering process .16
7.3.6 Measurement of local distortion (only for heat soaked tempered safety
glass which was vertically tempered) .16
7.3.7 Limitation on overall bow, roller waves and edge lift for heat soaked
tempered safety glass which was horizontally tempered .17
7.3.8 Limitation on overall bow, wave and perimeter deformation for heat
soaked tempered safety glass manufactured by air cushion process .18
7.3.9 Limitation on overall bow and local distortion for heat soaked tempered
safety glass which was vertically tempered .18
7.3.10 Other distortions .18
8 Edge work, holes, notches and cut-outs.19
8.1 General .19
8.2 Edge working of glass for tempering .19
8.3 Profiled edges.20
8.4 Round holes .20
8.4.1 General.20
8.4.2 Diameter of holes .20
8.4.3 Limitations on position of holes .20
8.4.4 Tolerances on hole diameters .21
8.4.5 Tolerances on position of holes .22
8.5 Holes/others .23
8.6 Notches and cut-outs .23
8.7 Shaped panes .23
9 Fragmentation test .23
9.1 General .23
9.2 Dimensions and number of test specimens .23
9.3 Test procedure .24
9.4 Assessment of fragmentation .24
9.5 Minimum values from the particle count .25
9.6 Selection of the longest particle .25
9.7 Maximum length of longest particle .25
9.8 Test Report .26
10 Other physical characteristics .26
10.1 Optical distortion .26
10.1.1 Heat soaked tempered safety glass produced by vertical tempering .26
10.1.2 Heat soaked tempered safety glass produced by horizontal tempering .26
10.2 Anisotropy (iridescence) .26
10.3 Thermal durability .26
10.4 Mechanical strength .27
10.5 Surface pre-stress .27
11 Marking .27
12 Packaging .28
Annex A (informative) Pendulum impact test methods .29
Annex B (informative) Alternative method for the measurement of roller wave distortion .30
Annex C (informative) Example of particle count .32
Annex D (informative) Method for the measurement of the surface pre-stress of heat
soaked tempered safety glass .34
Annex E (informative) In-line heat soak process control .36
Annex F (informative) Heat soak process system calibration test .38
Bibliography .48
iv © ISO 2017 – All rights reserved
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www .iso .org/ patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO’s adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following
URL: w w w . i s o .org/ iso/ foreword .html.
This document was prepared by Technical Committee ISO/TC 160, Glass in building, Subcommittee SC 1,
Product considerations.
Introduction
Heat soaked tempered soda lime silicate safety glass has a safer breakage behaviour when compared
with annealed glass. This behaviour is a direct result of the high surface pre-stress.
It also has a known level of residual risk of spontaneous breakage arising from the possible presence of
critical nickel sulfide (NiS) inclusions in the thermally toughened soda lime silicate glass.
Heat soaked tempered soda lime silicate safety glass has a known behaviour under accident human
impact together with known mechanical and thermal stress resistance.
Other requirements, not specified in this document, can apply to heat soaked tempered soda lime
silicate safety glass which is incorporated into assemblies, e.g. laminated glass or insulating glass
units, or undergo an additional treatment, e.g. coating. The additional requirements are specified in the
appropriate glass product standard. Heat soaked tempered soda lime silicate safety glass, in this case,
does not lose its mechanical or thermal characteristics.
NOTE 1 ISO/TC 160/SC 2 is producing standards for the determination of the design strength of
glass and is preparing a design method.
NOTE 2 In Europe, instead of “heat soaked tempered”, the term “heat soaked thermally
toughened” is used.
vi © ISO 2017 – All rights reserved
INTERNATIONAL STANDARD ISO 20657:2017(E)
Glass in building — Heat soaked tempered soda lime
silicate safety glass
1 Scope
This document specifies product definitions, product characteristics, i.e. tolerances, flatness, edgework,
etc., fracture characteristics, including fragmentation, and the physical and mechanical characteristics
of flat heat soaked tempered soda lime silicate safety glass for use in buildings.
This document does not cover curved (bent) glass according ISO 11485.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 1288-3, Glass in building — Determination of the bending strength of glass — Part 3: Test with
specimen supported at two points (four point bending)
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at http:// www .electropedia .org/
— ISO Online browsing platform: available at http:// www .iso .org/ obp
3.1
heat soaked tempered soda lime silicate safety glass
heat soaked tempered safety glass
glass within which a permanent surface compressive stress, additionally to the basic mechanical
strength, has been induced by a controlled heating and cooling process in order to give it greatly
increased resistance to mechanical and thermal stress and prescribed fragmentation characteristics
and which has a known level of residual risk (3.2) of spontaneous breakage due to the presence of critical
nickel sulphide (NiS) inclusions
3.2
level of residual risk
risk of spontaneous breakage of heat soaked thermally toughened soda lime silicate safety glass, on a
statistical basis, due to the presence of critical nickel sulphide inclusions
Note 1 to entry: It is considered that the level of residual risk is no more than one breakage per 400 tonnes of heat
[6][7][8]
soaked thermally toughened soda lime silicate safety glass .
3.3
flat heat soaked tempered safety glass
heat soaked tempered (thermally toughened) glass which has not been deliberately given a specific
profile during manufacture
3.4
enamelled heat soaked tempered safety glass
heat soaked tempered (thermally toughened) glass which has a ceramic frit fired into the surface
during the tempering (toughening) process
Note 1 to entry: After tempering, the ceramic frit becomes an integral part of the glass.
Note 2 to entry: The application of the ceramic frit may be by a continuous application or discontinuous, e.g.
screen printing.
3.5
horizontal tempering process
process in which the glass is supported on horizontal rollers
3.6
air cushion process
process in which the glass is supported by an air cushion with or without additional rollers
Note 1 to entry: In this process, the glass will be between horizontal and 45° of horizontal.
3.7
vertical tempering process
process in which the glass is suspended by tongs
3.8
edge deformation
deformation of the edge caused by the tong marks
3.9
edge lift
edge dip
distortion produced in heat soaked tempered safety glass (3.1) which was horizontally tempered, at the
leading and trailing edge of the plate, as a result of the glass during the tempering (toughening) process
not being supported by a roller
Note 1 to entry: This is a distortion produced by a deviation from surface flatness.
3.10
perimeter deformation
distortion around the edge of heat soaked tempered safety glass (3.1) manufactured by air cushion
process (3.6)
3.11
local distortion
local deformation underneath the tong marks of heat soaked tempered safety glass (3.1) which was
vertically tempered
3.12
overall bow
deformation of the whole pane of heat soaked tempered safety glass (3.1) caused by the heating and
cooling process
3.13
roller wave distortion
periodic distortion produced in heat soaked tempered safety glass (3.1) which was horizontally tempered
as a result of the glass during tempering process being in contact with the rollers
Note 1 to entry: This is a surface distortion produced by a reduction in surface flatness.
2 © ISO 2017 – All rights reserved
3.14
wave distortion
distortion produced in heat soaked tempered safety glass (3.1) manufactured by air cushion process (3.6)
as a result of the tempering process
3.15
heat soak process
heat treatment after the tempering process during which majority of NiS inclusions is removed resulting
in a known level of critical NiS inclusions in the heat soaked tempered soda lime silicate safety glass
3.16
in-line heat soak process
heat soak process (3.15) which follows immediately after the quenching process whereby the glass
temperature is directly reduced from quenching to the heat soak temperature in an in-line heat soak oven
3.17
off-line heat soak process
heat soak process (3.15) carried out after the quenching process whereby the glass is cooled down to
room temperature and heated up again to the heat soak temperature in an off-line heat soak oven
4 Glass products
Heat soaked tempered safety glass is made from a monolithic glass generally corresponding to one of
the following standards:
— basic soda lime silicate glass products according to ISO 16293-1;
— float glass according to ISO 16293-2;
— patterned glass according to ISO 16293-5;
— coated glass according to ISO 11479-1.
NOTE For drawn sheet glass, an ISO standard is not available. Therefore, see EN 572–4 or national standards.
Other nominal thicknesses of glass than those covered in the above standards are possible.
5 Manufacturing processes
5.1 General
Heat soaked tempered safety glass is manufactured as follows.
Basic soda lime silicate glass products (see Clause 4) are cut to size, shaped and edgeworked (see
Clause 8).
The prepared glass panes are then tempered (see 5.2).
The tempered panes are then subjected to an off-line or in-line heat soak process cycle (see 5.3.1 and 5.3.2)
After manufacture the heat soaked tempered safety glass shall comply with the fragmentation test (see
Clause 9) and mechanical strength requirement (see 10.4).
5.2 Tempering process
The cut, shaped and edgeworked glasses are tempered. The heat soaked tempered glass shall comply
with the flatness criteria for horizontal or vertical tempering or the air cushion process (see 7.3).
The heat soaked tempered safety glass shall have a level of fragmentation that will ensure that after the
glass has been through the heat soak process, and subsequently tested to the fragmentation test (see
Clause 9), it shall comply with 9.5.
5.3 Heat soak process cycles
5.3.1 Off-line process
5.3.1.1 General
The heat soak process cycle consists of a heating phase, a holding phase and a cooling phase (see
Figure 1).
Key
T glass temperature at any point, °C
t time, h
1 first glass to reach 250 °C
2 last glass to reach 250 °C
a
heating phase
b
holding phase
c
cooling phase
d
ambient temperature
Figure 1 — Heat soak process cycle
5.3.1.2 Heating phase
The heating phase commences with all the glasses at ambient temperature and concludes when the
surface temperature of the last glass reaches 250 °C. The maximum heating rate is 3 °C per min. The
time to reach this temperature is defined in the calibration process. This time will be dependent on
the size of the oven, the amount of glass to be treated, the separation between glasses and the heating
system capacity.
The glass separation and rate of heating should be controlled to minimize the risk of glass breakage as
a result of thermal stress.
To facilitate economic heating, the air temperature within the oven may exceed 290 °C. However, the
glass surface temperature shall not be allowed to exceed 290 °C. The period of glass surface temperature
in excess of 270 °C shall be minimized.
NOTE Care should be taken to ensure the maximum temperature of the glass does not exceed 270 °C as there
is a possibility of the nickel sulphide inclusion reconverting.
4 © ISO 2017 – All rights reserved
5.3.1.3 Holding phase
The holding phase commences when the surface temperature of all the glasses has reached a
temperature of 250 °C. The minimum duration of the holding phase is 2 h.
Precise oven control is necessary in order to ensure that the glass surface temperature shall be
maintained in the range of 260 °C ± 10 °C during the holding phase.
5.3.1.4 Cooling phase
The cooling phase commences when the last glass to reach 250 °C has completed its holding phase, i.e.
been held for two hours at 260 °C ± 10 °C. During this phase, the glass temperature shall be brought
down to ambient temperature.
The cooling phase can be concluded when the air temperature in the oven reaches 70 °C.
The rate of cooling should be controlled to minimize the risk of glass breakage as a result of thermal stress.
5.3.1.5 Heat soak process system
5.3.1.5.1 General
The heat soak process system consists of the following:
— oven (see 5.3.1.5.2);
— glass support (see 5.3.1.5.2);
— separation system (see 5.3.1.5.4).
The oven shall be calibrated (see 5.3.1.5.5 and Annex F) and this determines the method of operation of
the heat soak process system during manufacture of heat soaked tempered safety glass.
5.3.1.5.2 Oven
The oven shall be heated by convection and shall allow an unhindered air circulation around each glass
pane. In the event of glass breakage, the airflow shall not be hindered. The airflow in the oven shall be
led parallel to the glass surfaces.
The openings for the air ingress/egress should be designed to ensure that fragments of broken glass do
not cause blockages.
5.3.1.5.3 Glass support
Glasses may be supported vertically or horizontally. The glasses shall not be fixed or clamped; they
have to be supported to allow free movement.
NOTE Vertically means true vertical or up to 15° either side of true vertical.
The distance between glasses affects the airflow, heat exchange and the heating time. Glass to glass
contact shall not be allowed.
5.3.1.5.4 Glass separation
The glasses shall be separated in a manner that does not hinder the airflow. The separators shall also
not hinder the airflow, e.g. see Figure 2.
Dimensions in millimetres
Figure 2 — Example of a vertical glass separator
The minimum separation of the glasses shall be determined during the calibration of the oven, see
5.3.1.5.5 and Annex F.
NOTE 1 Generally, a minimum separation of 20 mm is recommended (see Figure 3).
NOTE 2 If glasses of very different sizes are put on the same stillage, they will require greater separation in
order to prevent glass breakage when the furnace is opened after the heat soak process. The same applies to
glasses with holes, notches and cut-outs.
Figure 3 — Recommended separation between glass
6 © ISO 2017 – All rights reserved
The positioning of the separators, material of the manufacture and their shape shall be specified during
the calibration test of the oven and shall be reproduced during the manufacturing process.
5.3.1.5.5 Calibration
The heat soak system, e.g. oven, glass separation, separators, etc., shall be calibrated. See Annex F.
The calibration shall determine the heating phase of the process, glass separation distance, the
positioning, material and shape of separators, the type and positioning of stillage(s) and define the
operating conditions for use during manufacture.
5.3.2 In-line process
5.3.2.1 General
The in-line heat soak process cycle consists of only a holding phase subsequent to the quenching (see
Figure 4).
Key
T glass temperature at any point, °C
t time, minutes
a
heating phase for tempering
b
quenching phase for tempering
c
holding phase
d
cooling phase
Figure 4 — In-line heat soak process cycle
5.3.2.2 Holding phase
The holding phase commences when the glass temperature has reached a temperature of between
200 °C and 240 °C. The duration of the holding phase is 12 min or more.
Precise oven control is necessary in order to ensure that the glass temperature is maintained in the
range of 220 °C ± 20 °C during the holding phase.
The glass which has completed its holding phase (has been held at 220 °C ± 20 °C for 12 min or longer) is
cooled down by exposure to ambient temperature.
5.3.2.3 In-line heat soak process system
5.3.2.3.1 General
The in-line heat soak process system only consists of the oven subsequent to the quenching furnace.
5.3.2.3.2 Oven
The oven temperature shall be maintained in the range of 220 °C ± 20 °C at all times. The entrance of
the oven shall be designed to ensure that the temperature in the oven does not fall rapidly when the
glass is moved in and out.
5.3.2.3.3 Glass temperature control
Precise glass temperature control is necessary before the glass enters the in-line heat soak oven in order
to ensure that the glass is kept in the range of 220 °C ± 20 °C during the holding phase (see Annex E).
6 Fracture characteristics
6.1 General
In the event of breakage, heat soaked tempered safety glass fractures into numerous small pieces, the
edges of which are generally blunt.
Fragmentation in service may not correspond exactly to that described in Clause 9 due to restraint
from fixing and external actions or due to the cause of fracture.
There can be different fragmentations if heat soaked tempered glass is used in laminated glass.
6.2 Accidental human impact
6.2.1 When subjected to an accidental human impact, heat soaked tempered safety glass will either
not break or break in a manner that will reduce the risk of cutting and piercing injuries.
6.2.2 Heat soaked tempered safety glass can be classified by the use of a pendulum impact test. When
tested by this type of test, the safe breakage criteria employed for heat soaked tempered safety glass is
that the 10 largest crack-free particles collected within 3 min after the impact shall weigh no more than
6 500 mm of the original test piece.
6.2.3 The quoted break criteria is taken from the standards given in Annex A. Annex A lists the test
methods presently employed to classify this product.
NOTE The safe breakage criteria are different to the fragmentation criteria used to determine that the
product complies with its definition.
6.3 Fragmentation
This test method is employed to demonstrate that the heat soaked tempered safety glass breaks in the
manner expected of this product. The fragmentation test (see Clause 9) details the minimum number
of crack-free particles that shall be in a set area, i.e. 50 mm × 50 mm, and the dimension of the largest
acceptable splinter.
This fragmentation behaviour ignores any influence of support conditions and is a representation of
the effect of the surface pre-stress.
These properties are not size dependent.
8 © ISO 2017 – All rights reserved
7 Dimensions and tolerances
7.1 Nominal thickness and thickness tolerances
The nominal thicknesses and thickness tolerances in Table 1 are those given in the relevant product
standards (see Clause 4).
Table 1
Nominal thickness Float glass tolerances Patterned glass tolerances
mm mm mm
2 ±0,2 Not manufactured
3 ±0,3 ±0,5
4 ±0,3 ±0,5
5 ±0,3 ±0,5
6 ±0,3 ±0,5
8 ±0,6 ±0,8
10 ±0,6 ±1,0
12 ±0,8 ±1,5
15 ±0,8 ±1,5
19 ±1,2 ±1,5
22 ±1,2 ±2,0
25 ±1,2 Not manufactured
The thickness of a pane shall be determined as for the basic product. The measurement shall be taken
at the centres of the 4 sides, and away from the area of any tong marks (see Figure 6), which may be
present.
7.2 Width and length (sizes)
7.2.1 General
When heat soaked tempered safety glass dimensions are quoted for rectangular panes, the first
dimension shall be the width, B, and the second dimension the length, H, as shown in Figure 5. It shall
be made clear which dimension is the width, B, and which is the length, H, when related to its installed
position.
Figure 5 — Examples of width, B, and length, H, relative to the pane shape
For heat soaked tempered safety glass manufactured from patterned glass, the direction of the pattern
should be specified relative to one of the dimensions.
7.2.2 Maximum and minimum sizes
For maximum and minimum sizes, the manufacturer should be consulted.
7.2.3 Tolerances and squareness
The nominal dimensions for width and length being given, the finished pane shall not be larger than the
nominal dimensions increased by the tolerance, t, or smaller than the nominal dimensions reduced by
the tolerance, t. Limits are given in Table 2.
The squareness of rectangular glass panes is expressed by the difference between its diagonals. The
difference between the two diagonal lengths of the pane of glass shall not be larger than the deviation
limit, v, as specified in Table 3.
Table 2 — Tolerances, t, on width, B, and length, H
Dimensions in millimetres
Nominal glass thickness
Nominal dimension
of side, B or H
2 3 4 5 6 8 10 12 15 19 25
≤ 1 000 ±2 ±3 ±4 ±5
1 000 < B or H ≤ 2 000 ±3 ±4 ±5
2 000 < B or H ≤ 3 000 ±4 ±6
3 000 < B or H ±4 ±5 ±6
10 © ISO 2017 – All rights reserved
Table 3 — Limit deviations, v, for the difference between diagonals
Dimensions in millimetres
Nominal dimension Nominal glass thickness
of side, B or H
2 3 4 5 6 8 10 12 15 19 25
≤ 1 000 4 6 8 10
1 000 < B or H ≤ 2 000 6 8 10
2 000 < B or H ≤ 3 000 8 12
3 000 < B or H 8 10 12
7.2.4 Edge deformation produced by vertical tempering
The tongs used to suspend the glass during tempering result in surface depressions, known as tong
marks (see Figure 6). The centres of the tong marks are situated up to a maximum of 20 mm from the
edge. A deformation of the edge less than 2 mm can be produced in the region of the tong mark and
there may also be an area of optical distortion.
Key
1 deformation in the tolerances of Table 2
2 up to 20 mm
3 tong mark
4 100 mm radius maximum area of optical distortion
Figure 6 — Tong mark deformation
7.3 Flatness
7.3.1 General
By the very nature of the tempering process, it is not possible to obtain a product as flat as annealed
glass. This difference in flatness depends on the type of glass, e.g. coated, patterned, etc., glass
dimensions, i.e. the nominal thickness, the dimensions, the ratio between the dimensions and the type
of the tempering process employed.
There are six kinds of distortion:
— overall bow (see Figure 7);
— roller wave distortion (only for heat soaked tempered safety glass which was horizontally tempered)
(see Figure 8);
— edge lift (only for heat soaked tempered safety glass which was horizontally tempered) (see
Figure 9);
NOTE 1 Overall bow, roller wave and edge lift can, in general, be accommodated by the framing system.
— local distortion (only for heat soaked tempered safety glass which was vertically tempered) (see
Figure 10);
NOTE 2 Local distortion needs to be allowed for within the glazing materials and the weather seals. For
special requirements, the manufacturers should be consulted.
— wave distortion (for heat soaked air cushion tempered safety glass only) (see Figure 8);
— perimeter deformation (for heat soaked air cushion tempered safety glass only) (see Figure 14).
Key
1 deformation for calculating overall bow
2 B or H or diagonal length
3 heat soaked tempered safety glass
Figure 7 — Representation of overall bow
Key
1 roller wave distortion
Figure 8 — Representation of wave or roller wave distortion
12 © ISO 2017 – All rights reserved
Key
1 straight edge
2 edge lift
3 heat soaked tempered safety glass
Figure 9 — Representation of edge lift
Key
1 local distortion
2 heat soaked tempered safety glass
Figure 10 — Representation of local distortion
7.3.2 Measurement of overall bow
The pane of glass shall be placed in a vertical position and supported on its longer side by two load
bearing blocks at the quarter points (see Figure 11).
For glass thinner than 4 mm nominal thickness, a solid back support with an angle between 3° and 7°
from the vertical can be used.
The deformation shall be measured along the edges of the glass and along the diagonals, as the
maximum distance between a straight metal ruler, or a stretched wire, and the concave surface of the
glass (see Figure 7).
The value for the bow is then expressed as the deformation, in millimetres, divided by the measured
length of the edge of the glass, or diagonal, in millimetres, as appropriate.
The measurement shall be carried out at room temperature.
Dimensions in millimetres
Key
1 B or H
2 (B or H)/2
3 (B or H)/4
4 heat soaked tempered safety glass
5 load bearing block
Figure 11 — Support conditions for the measurement of overall bow
NOTE Special care has to be taken for large and thin panes because they can show a buckling which is
different from an overall bow caused by the tempering process. Results from this test method for glasses thinner
than 4 mm may be inaccurate.
7.3.3 Measurement of wave or roller wave distortion
7.3.3.1 General
The wave or roller wave distortion is measured by means of a straightedge, or equivalent, being placed
at right angles to the wave or roller wave and bridging from peak to peak of the wave (see Figure 12).
NOTE This subclause deals with measurement using a straightedge and feeler gauges. An alternative method
is described in Annex B.
7.3.3.2 Apparatus
A straightedge: length of between 300 mm and 400 mm.
NOTE The actual length of straight edge required will depend upon the wavelength of the wave or roller wave.
Feeler gauges: various thicknesses in units of 0,05 mm.
7.3.3.3 Method
Place the straightedge so that it bridges across adjacent peaks. Insert the feeler gauge between the
glass surface and the straightedge. Increase the thickness of the feeler gauges until they just fill the gap
between glass surface and the straight edge. Record the thickness of feeler gauge(s) to an accuracy of
0,05 mm.
Repeat the measurement at several places over the glass surface.
14 © ISO 2017 – All rights reserved
The measured wave or roller wave distortion is the maximum value measured. The maximum allowable
values are given in Table 4 and Table 6.
7.3.3.4 Limitations
The following limitations apply.
— The wave or roller wave can only be measured on panes with a dimension greater than 600 mm
measured at right angles to the waves or roller waves.
— The wave or roller wave cannot be measured in an exclusion area that is 150 mm from the edges of
the pane. The apparatus should not be used in the area of these 150 mm.
— Panes with an overall bow shall be laid on a flat support. This will allow gravity to flatten out the
overall bow and hence give a truer result for the wave or roller wave.
Key
1 straight edge
2 wave or roller wave distortion
3 heat soaked tempered safety glass
Figure 12 — Measurement of wave or roller wave distortion
7.3.4 Measurement of edge lift (only for heat soaked tempered safety glass which was
horizontally tempered)
7.3.4.1 Apparatus
A straightedge: length of between 300 mm and 400 mm.
NOTE The actual length of straightedge required will depend upon the wavelength of the roller wave.
Feeler gauges: various thicknesses in units of 0,05 mm.
7.3.4.2 Method
The glass shall be placed on a flat support with the edge lift overhanging the edge of the support. The
overhanging distance should be between 5 cm and 10 cm.
The straight edge is placed on the peaks of the roller waves and the gap between the ruler and the glass
measured using a feeler gauge (see Figure 13).
The maximum values for edge lift are given in Table 5.
The values in Table 4 only apply to heat soaked tempered safety glass having edgework complying with
Figure 16 to Figure 19. For profiled edges or other types of edgework, contact the manufacturer.
Dimensions in millimetres
Key
1 straight edge
2 edge lift
3 heat soaked tempered safety glass
4 flat support
Figure 13 — Measurement of edge lift
7.3.5 Measurement of perimeter deformation of glass produced by air cushion tempering
process
Place the glass on a flat surface with the concave side facing upwards. See Figure 14.
A 100 mm straight edge is laid on the pane at right angles to the edge. The gap between the ruler and
the glass is measured using a feeler gauge (see Figure 14). The perimeter deformation is the maximum
distance between the surface of the pane and the straight edge.
The maximum allowable values for perimeter deformation are given in Table 7.
Dimensions in millimetres
Key
1 straight edge
2 perimeter deformation
3 glass
Figure 14 — Measurement of perimeter deformation
7.3.6 Measurement of local distortion (only for heat soaked tempered safety glass which was
vertically tempered)
Local distortion can occur over relatively short distances on the edges with tong mark
...
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