Glass article

Many authors have shown that residual stresses in glass articles can be formally considered as the thermal stresses due to a certain fictitious temperature field. In the general case... 

Molding. Many glass articles ate made by shaping a glass gob by forcing it under pressure against a mold. The source of pressure and type of mold vary with the application. 

Small, complex-shaped glass articles such as thread guides for the textile industry and television gun mounts for the electronics industry are made by the multiform process. The dry-milled powder is mixed with an inorganic binder and a fluid vehicle, and then atomi2ed by a spray dryer into small, dried agglomerates of glass powder and binder with good flow characteristics. They are subsequently pressed to the desired shape and fired. 

Stress birefringence The presence of stress in glass articles may be monitored readily since stressed glass is birefringent. Standard methods exist for these measurements. 

Whole article tests Grain tests are open to the criticism that they do not necessarily reflect the behaviour of the finished product in service, hence various tests on complete glass articles have been developed. These are normally carried out under accelerated conditions, and on completion various relevant factors are determined, such as loss in weight, alkali or other constituents extracted, the weight of soluble and insoluble materials in the extract and an assessment of surface condition. The advent of the electron microscope as a standard tool has made the latter study much more objective. 

Procedure for classifying glass articles according to chemical and thermal properties. Not yet published in its final form. May be adopted by ISO. 

Soda (composed of sodium oxide) and potash (composed of potassium oxide) are relatively easy to obtain or to make, work, and handle. Although they do not occur naturally, they could be quite easily prepared in the past by burning some plants (see Textbox 28). Both these oxides were used as fluxes for making early types of glass articles, particularly small vessels and decorative objects. 

From analyses of ancient Egyptian and Roman glass articles, it is shown that generally the glass from these sources was a soda-lime glass with rather high soda content as compared with modern soda-lime glass. 

Heralux tradename of Heraeus quartz glass articles. 

Lead glass suitable for fine glass articles (crystal glass), optical glasses and television tubes... 

Increasing the strength of glass articles by compression strain in the glass surface (quenching, ion exchange)... 

The precursor glass article may be annealed and cooled to room temperature for inspection (it is usually transparent), or it may be cooled to the nucleation temperature... 

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