GLASS 651 



The following recipe for crown-glass is excellent : Partg 



5 atoms of silica (2 ?) . . . ' . . .80 



1 carbonate of soda 54 



5 silica . ,80 



1 carbonate of lime . . . . .50 



1 atom of carbonate of baryta . .. ..''-'. .98 

 5 atoms of silica ' . 80 



Silicates of lime and baryta per se, or even combined, are very refractory ; but they 

 vitrify well along with a third silicate, such as that of soda or potash. 



The following are additional recipes for making different kinds of glass : 



1. Bottle glass. 1 1 Ibs. of dry Glauber salt ; 12 of soaper salts ; a half bushel of 

 waste soap ashes ; 56 Ibs. of sand ; 22 of glass skimmings ; 1 cwt. of green broken 

 glass ; 25 Ibs. of basalt. This mixture affords a dark green glass. 



2. Yellow or white sand, 100 parts ; kelp, 30 to 40 ; lixiviated wood ashes, from 

 160 to 170 ; fresh wood ashes, 30 to 40 ; potter's clay, 80 to 100 ; cullet or broken 

 glass, 100. If basalt be used, the proportion of kelp may be diminished. 



In two bottle-glass houses in the neighbourhood of Valenciennes, an unknown in- 

 gredient, sold by a Belgian, was employed, which he called spar. This was discovered 

 by chemical analysis to be sulphate of baryta. The glass-makers observed that the 

 bottles which contained some of this substance were denser, inore homogeneous, more 

 fusible, and worked more kindly than those formed of the common materials. When 

 one equivalent of the silicate of baryta = 123, is mixed with three of the silicate of 

 soda (3 x 77'6) 232 f 8, and exposed in a proper furnace, vitrification readily ensues, 

 and the glass may be worked a little under a cherry-rod heat, with as much ease as 

 a glass of lead, and has nearly the same lustre. 



3. Green window-glass, or broad glass. 11 Ibs. of dry Glauber salt; 10 of soaper 

 salts ; half a bushel of lixiviated soap waste ; 50 Ibs. of sand ; 22 of glass-pot 

 skimmings ; 1 cwt. of broken green glass. 



4. Crown-glass. 300 parts of fine sand ; 200 of good soda ash ; 33 of lime ; from 

 250 to 300 of broken glass ; 60 of white sand ; 30 of purified potash ; 15 of saltpetre 

 (1 of borax); g- of arsenious acid. 



5. Nearly white table-glass. 20 Ibs. of potashes; 11 of dry Glauber salt; 16 of 

 soaper salt; 55 of sand; 140 of cullet of the same kind. 



Another. 100 Ibs. of sand; 235 of kelp; 60 of wood ashes; Ig- of manganese; 

 100 of broken glass. 



6. White table-glass. 40 Ibs. of potashes; 11 of chalk; 76 of sand; of manga- 

 nese ; 95 of white cullet. 



Another. 50 Ibs. of purified potashes ; 100 of sand; 20 of chalk; 2 of saltpetre. 

 Bohemian table- or plate-glass is made with 63 parts of quartz; 26 of purified 

 potashes ; 1 1 of sifted slaked lime ; and some cullet. 



7. Crystal glass. 60 parts of purified potashes; 120 of sand; 24 of chalk; 2 of 

 saltpetre ; 2 of arsenious acid ; i of manganese. 



Another. 70 parts of purified pearlashes; 120 of white sand; 10 of saltpetre; 

 of arsenious acid ; ^ of manganese. 



A third. 67 parts of sand ; 23 of purified pearlashes ; 10 of sifted slaked lime ; 

 of manganese ; (5 to 8 of red lead). 



A fourth. 120 parts of white sand ; 50 of red lead ; 40 of purified pearlashes ; 

 20 of saltpetre ; of manganese. 



A fifth. 120 parts of white sand; 40 of purified pearlashes ; 35 of red lead; 13 

 of saltpetre ; ^ of manganese. 



A sixth. 30 parts of the finest sand; 20 of red lead; 8 of purified pearlashes ; 

 2 of saltpetre ; a little arsenious acid and manganese. 



A seventh. 100 parts of sand; 45 of rod lead; 35 of purified pearlashes; \ of 

 manganese ; of arsenious acid. 



8. Plate-glass. 300 parts of very white sand ; 100 of dry purified soda ; 43 of 

 carbonate of lime; 1 of manganese; 300 of cullet. 



Another. 720 parts of finest sand ; 450 of purified soda ; 80 of quicklime ; 25 of 

 saltpetre ; 425 of cullet. 



A little borax has also been prescribed ; much of it communicates an exfoliating 

 property to glass. 



PRACTICAL DETAILS OF THE MANUFACTUBE OF GLASS. 



^ There are five different species of glass, each requiring a peculiar mode of fabrica- 

 tion and peculiar materials : 1. The coarsest and simplest form of this manufacture 

 is bottle-glass. 2. Next to it in cheapness of material may be ranked broad or spread 

 window-glass. An improved article of this kind is now made near Birmingham, 



