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The Soda-Lime Glass Formula
Pressed ware from about 1870 on changed in both quality of design and in composition. In 1864 William Leighton of Wheeling, West Virginia, formerly from the New England Glass Company of Cambridge, brought out a formula which omitted the expensive ingredient of lead. Glass made from his soda-lime mix did not have the brilliance of the earlier lead ware. It was not as suitable for cutting and engraving, nor even for the simple early pressed glass patterns, which are so attractive in articles of clear lead glass. Nevertheless hundreds of patterns continued to be made in clear glass from Leighton's formula.
The new soda-lime formula, the new improvements in machinery, the new buying power of the public, all produced a boom in the pressed glass business. Clear blown glass with simple cut or engraved designs was still made for an exclusive few. (As yet the machine had not encroached on this craft.) Colored blown glass was developed into the so-called "art glasses" and ornamental ware, some of which achieved ornateness that surpassed the fanciest of the pressed products. Mass production in glass, however, consisted of colored pressed ware with elaborate designs. New patterns were constantly brought out. Those that proved popular were retained longer and manufactured in a greater variety of items. The same patterns were often made in different colors and with variations, usually at different factories. Some of the old patterns like Ashburton were produced for a while from the new formula, but the absence of lead spoiled their earlier charm.
Briefly, there are three main types of decoration for pressed ware. First, clear glass was decorated solely by the pattern impressed on it in the mold. The pattern always appears in low relief and the inside of the article is smooth. This type has been used continuously down to the present time. Second, the same technique was used on a transparent or opaque colored glass. Here the appeal lies in both pattern and color. This type includes opaque white ware such as the Blackberry pattern. Colored pressed ware was made in quantities after the new soda-lime formula was invented. Third, clear colored or opaque glass has the pattern impressed upon it and is also decorated by other means. The multiple-decorated type belongs to the late Victorian period.