ASTM C912-93(2008)
(Practice)Standard Practice for Designing a Process for Cleaning Technical Glasses
Standard Practice for Designing a Process for Cleaning Technical Glasses
SIGNIFICANCE AND USE
Many of the low-silica technical glasses which contain soluble or reactive oxides require processing or involve applications that require cleaning. Very often these cleaning procedures have evolved over several decades and are considered an art. They usually contain numerous steps, some of questionable validity. It is the premise of this practice that cleaning glass can be more scientific. Design of a cleaning procedure should involve (1) a definition of the soil to be removed, (2) an awareness of the constraints imposed by the glass composition, and (3) a rational selection of alternative methods that will remove the soil and leave the glass in a condition suitable for its intended application. This practice provides information to assist in step (3). General references on glass cleaning and on various methods of evaluating cleanliness and associated information has been published.
SCOPE
1.1 This practice covers information that will permit design of a rational cleaning procedure that can be used with a glass that is somewhat soluble in many aqueous chemical solutions. Typically, this type of glass is used in applications such as optical ware, glass-to-metal seals, low dielectric loss products, glass fibers, infrared transmitting products, and products resistant to metallic vapors.
1.2 In most cases, this type of glass contains high concentrations of oxides that tend to react with a number of aqueous chemicals. Such oxides include B2O3, Al2O3, R2O, RO, La2O3, ZnO, PbO, P2O5, and Fe2O3. The more conventional high-silica glasses are usually more chemically resistant, but the cleaning principles outlined here also apply to them.
1.3 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 and health practices and determine the applicability of regulatory limitations prior to use. Specific hazard statements are given in Section 4 and Table 1.
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Designation:C912–93(Reapproved 2008)
Standard Practice for
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Designing a Process for Cleaning Technical Glasses
This standard is issued under the fixed designation C912; 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 (ϵ) indicates an editorial change since the last revision or reapproval.
1. Scope remove the soil and leave the glass in a condition suitable for
its intended application. This practice provides information to
1.1 This practice covers information that will permit design
assist in step (3). General references on glass cleaning and on
of a rational cleaning procedure that can be used with a glass
various methods of evaluating cleanliness and associated
that is somewhat soluble in many aqueous chemical solutions.
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information has been published.
Typically, this type of glass is used in applications such as
optical ware, glass-to-metal seals, low dielectric loss products,
4. Hazards
glass fibers, infrared transmitting products, and products resis-
4.1 Manyofthechemicalsthatcanbeusedincleaningglass
tant to metallic vapors.
are hazardous. This is true of most of the aqueous chemicals
1.2 In most cases, this type of glass contains high concen-
discussed in Section 5 and shown in Table 1 as well as the
trations of oxides that tend to react with a number of aqueous
organic chemicals discussed in Section 6.
chemicals. Such oxides include B O ,Al O ,R O, RO, La O ,
2 3 2 3 2 2 3
4.2 Specialcareshouldbeusedwithhydrofluoricacid(HF),
ZnO, PbO, P O , and Fe O . The more conventional high-
2 5 2 3
which will react with glass generating heat. The vapors as well
silica glasses are usually more chemically resistant, but the
as the liquid destroy dermal tissue and can be fatal if inhaled.
cleaning principles outlined here also apply to them.
4.3 Concentrated acids can react violently if water is added
1.3 This standard does not purport to address all of the
into them. When it is necessary to dilute acid, add the acid to
safety concerns, if any, associated with its use. It is the
the water slowly and with constant stirring so that heat is never
responsibility of the user of this standard to establish appro-
allowed to concentrate locally in the solution.
priate safety and health practices and determine the applica-
4.4 Organic solvents may be flammable or toxic, or both.
bility of regulatory limitations prior to use. Specific hazard
Thresholdlimitvaluesforsomecommonsolventsareshownin
statements are given in Section 4 and Table 1.
Table 2. Note that the fluorocarbons are most likely to exhibit
2. Terminology toxic effects as a result of inhalation or skin absorption.
Benzene is not recommended as a solvent since it is a known
2.1 Definitions of Terms Specific to This Standard:
carcinogen.
2.1.1 technical glass—glasses designed with some specific
property essential for a mechanical, industrial, or scientific
5. Aqueous Solvents
device.
5.1 Selection—In using aqueous solvents for cleaning, gen-
3. Significance and Use erally two extreme choices are available. One is to select an
aqueous system that dissolves the soil to be removed, but has
3.1 Many of the low-silica technical glasses which contain
little effect on the glass. The other is to select a system that
soluble or reactive oxides require processing or involve appli-
dissolves the glass uniformly, thus undercutting the soil and
cations that require cleaning. Very often these cleaning proce-
leaving a chemically polished glass surface. It is best to avoid
dures have evolved over several decades and are considered an
a solvent that selectively attacks the glass, dissolving only
art.Theyusuallycontainnumeroussteps,someofquestionable
some components, or a solvent that produces a precipitate that
validity.Itisthepremiseofthispracticethatcleaningglasscan
adheres to the surface to be cleaned.
be more scientific. Design of a cleaning procedure should
5.2 Minimum Glass Dissolution:
involve (1) a definition of the soil to be removed, (2)an
5.2.1 Water is the most frequently used aqueous solvent.
awareness of the constraints imposed by the glass composition,
Even this can attack some glasses appreciably.
and (3) a rational selection of alternative methods that will
5.2.2 Try to choose an aqueous system that completely
removes the soil with minimal effect on the underlying glass.
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Obviously, to achieve this the glass composition must be
This practice is under the jurisdiction of ASTM Committee C14 on Glass and
GlassProductsandisthedirectresponsibilityofSubcommitteeC14.02onChemical
Properties and Analysis.
Current edition approved Sept. 1, 2008. Published October 2008. Originally
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approved in 1979. Last previous edition approved in 2003 as C912
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