ASTM_C_912_-_93_2013.pdf

Designation:C91293(Reapproved 2013)Standard Practice forDesigning a Process for Cleaning Technical Glasses1This standard is issued under the fixed designation C912;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This practice covers information that will permit designof a rational cleaning procedure that can be used with a glassthat is somewhat soluble in many aqueous chemical solutions.Typically,this type of glass is used in applications such asoptical ware,glass-to-metal seals,low dielectric loss products,glass fibers,infrared transmitting products,and products resis-tant to metallic vapors.1.2 In most cases,this type of glass contains high concen-trations of oxides that tend to react with a number of aqueouschemicals.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 thecleaning principles outlined here also apply to them.1.3 This standard does not purport to address all of thesafety concerns,if any,associated with its use.It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.Specific hazardstatements are given in Section 4 and Table 1.2.Terminology2.1 Definitions of Terms Specific to This Standard:2.1.1 technical glassglasses designed with some specificproperty essential for a mechanical,industrial,or scientificdevice.3.Significance and Use3.1 Many of the low-silica technical glasses which containsoluble or reactive oxides require processing or involve appli-cations that require cleaning.Very often these cleaning proce-dures have evolved over several decades and are considered anart.They usually contain numerous steps,some of questionablevalidity.It is the premise of this practice that cleaning glass canbe more scientific.Design of a cleaning procedure shouldinvolve(1)a definition of the soil to be removed,(2)anawareness of the constraints imposed by the glass composition,and(3)a rational selection of alternative methods that willremove the soil and leave the glass in a condition suitable forits intended application.This practice provides information toassist in step(3).General references on glass cleaning and onvarious methods of evaluating cleanliness and associatedinformation has been published.24.Hazards4.1 Many of the chemicals that can be used in cleaning glassare hazardous.This is true of most of the aqueous chemicalsdiscussed in Section 5 and shown in Table 1 as well as theorganic chemicals discussed in Section 6.4.2 Special care should be used with hydrofluoric acid(HF),which will react with glass generating heat.The vapors as wellas the liquid destroy dermal tissue and can be fatal if inhaled.4.3 Concentrated acids can react violently if water is addedinto them.When it is necessary to dilute acid,add the acid tothe water slowly and with constant stirring so that heat is neverallowed to concentrate locally in the solution.4.4 Organic solvents may be flammable or toxic,or both.Threshold limit values for some common solvents are shown inTable 2.Note that the fluorocarbons are most likely to exhibittoxic effects as a result of inhalation or skin absorption.Benzene is not recommended as a solvent since it is a knowncarcinogen.5.Aqueous Solvents5.1 SelectionIn using aqueous solvents for cleaning,gen-erally two extreme choices are available.One is to select anaqueous system that dissolves the soil to be removed,but haslittle effect on the glass.The other is to select a system thatdissolves the glass uniformly,thus undercutting the soil andleaving a chemically polished glass surface.It is best to avoida solvent that selectively attacks the glass,dissolving onlysome components,or a solvent that produces a precipitate thatadheres to the surface to be cleaned.5.2 Minimum Glass Dissolution:5.2.1 Water is the most frequently used aqueous solvent.Even this can attack some glasses appreciably.1This practice is under the jurisdiction of ASTM Committee C14 on Glass andGlass Products and is the direct responsibility of Subcommittee C14.02 on ChemicalProperties and Analysis.Current edition approved Oct.1,2013.Published October 2013.Originallyapproved in 1979.Last previous edition approved in 2008 as C91293(2008)1.DOI:10.1520/C91293R13.2Campbell,D.E.,and Adams,P.B.,“Bibliography on Clean Glass:Supplement1,”Journal of Testing and Evaluation,Vol 14,No.5,September 1986,pp.260265.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 TABLE 1 Relative Solubility of Various Glass Component Oxides in HF,Other Inorganic Acids,and NaOH,in Concentrated Solutions atRoom TemperatureNOTE1Macro or min