isa-normaladvance-1913-00086

Description:	86THE NORMAL ADVANCESky blue glass contains from eight to twelvethousandths per cent of black oxide of copper,in addition to the foundation glass.Pale blue glass can be made by the partialoxidation of glass that is colored by iron.Deep blue color can be produced in glassby adding 0.15% of pure oxide of cobalt. Onepart of oxide of cobalt, added to 240 parts ofglass produces a very faint blue tinge. Thiscolor becomes more pronounced with the addition of more cobalt, until 18 per cent isreached, when the glass becomes black. Formaking the cobalt blue glass, a potash glass isalways used as a foundation. This blue glassis ground into a fine powder and is then usedin paints, and in the arts for coloring purposes.This powder is called smalt. Another way ofobtaining a deep blue is by using from threeand one-half to four per cent of zaffie in placeof the cobalt.Purple or amethyst glass is made by the addition of from two to two and one-half percent of black oxide of manganese. From fourto four and one-half per cent of saltpetre mustbe added to prevent reduction. Also, caremust be taken that the temperature is notraised too high, as the color varies with theheat, the purple tint turning to a brownish-red,then to yellow, and afterwards to green, asthe temperature increases.Green glass is produced in several ways. Itmay be made by using one to tw7o and one-halfper cent of iron oxide, the same amount ofcopper oxide, and one per cent of saltpeter,wrhich maintains the iron in the ferric state.When copper is used, a lead glass should beused as a foundation, as the color produced ismuch finer than with one containing no lead.A beautiful emerald green is produced by one-half to one per cent of oxide of chromium.This same color is produced by one or twoper cent of bichrome, or by two per cent ofoxide of antimony, with one per cent of cobalt.Two kinds of Bohemian green glass are madeby the use of mixtures of the oxides of nickeland uranium.Yellow glass may be produced by adding toone hundred parts of a fresh batch of soda-lime or potash-lime glass, two or three partsof stripped birch or elder bark, or the charcoalfrom them. The carbon formed from themmakes the color. Sulphur, also, is used forproducing yellow glass from either soda-limeor potash-lime foundations. The sulphurunites with the soda or potash to producesodium or potassium sulphide, which colors theglass. A simple receipt for this glass is: Sand,100 potash, 50 lime, 21 sulphur, 1.5 parts.A good yellow may also be produced by usingten parts of manganese dioxide and eight partsof ferric oxide, or by the addition of four toseven parts of antimonate of lead. Antimon-ate of potash is said to have the same effect.Bohemian glass is colored yellow by the useof glass of antimony, minium and oxide ofiron. Glass of antimony is made by roastingsulphide of antimony until antimonious acid isformed, and melting it with about five percent of the undecomposed sulphide of antimony. Silver is used to make the most beautiful and expensive yellow glass, but it is necessary, in using silver, to be very careful, as thesilver is only put on the surface, and must notpenetrate too far. Also, glass in which thereis some alumina must be used, as alumina isnecessary to produce the finest silver yellow.The surface of the glass is covered with amixture of finely powdered clay and silverchloride, and then the glass is re-heated. Before it reaches the melting point the silver penetrates a little ways into the glass. The coating on the glass is then scraped off, and theyellow color appears. Bohemian lime-potashglass is painted yellow w7ith the followingmixture: Silver chloride two to two and one-half parts red oxide of iron, ten parts sulphide of copper, five per cent and stannicoxide one part. After the design has beenapplied, the glass is retired and the silver mixture penetrates the glass, forming the yellowdesign with a color that varies from pale yellow7 to deep orange, according to the amountused. A beautiful canary-yellow shade isproduced by uranium. This glass is unique,
Source:	http://indstate.contentdm.oclc.org/cdm/ref/collection/isuarchive/id/34531
Collection:	Indiana State University Archives

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