History of Technology in India, Vol. I: From Antiquity to c. 1200 A.D. v1.c16.s3: Manufacture
History of Technology in India, Vol. I: From Antiquity to c. 1200 A.D. v1.c16.s3
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Manufacture
v1.c16.s3.1
Ingredients for glass in early days were river sand, crude natron or plant ashes and some colouring matter. Calcium carbonate was not added separately but particular sands were selected which contained lime. Such river sands are common in India.
v1.c16.s3.2
Production of Glass involved two stages. In the first stage sand and crude natron were heated at a temperature of 750°C when they were converted into frit. In the second stage the frit was converted to glass by heating it in crucibles upto a temperature of around 1100°C, till glass had become homogenous and clear.
v1.c16.s3.3
When finished, the glass was either poured straight into the mould for casting seals and slabs or it was poured in bits at a time and rolled into thick rods which were drawn into canes or strips.
v1.c16.s3.4
Table 1 — Colouring Agents used
v1.c16.s3.5
| 1. | Red and Liver red | Cu2O - Cuprous oxide |
| 2. | Brown | Fe2O3- Ferric oxide |
| 3. | Chocolate(opaque) | Cu2O+Fe2O3, - Cuprous oxide and Ferric oxide |
| 4. | Black | Ferri-sulphide/Ferrous oxide |
| 5. | White | SnO2-Tin oxide |
| 6. | Green - Bottle green | Mixture of CuO, FeO and Fe2O3 |
| 7. | Bluish green | Fe2O3+CuO |
| 8. | Turquoise Blue | CuO (Cupric oxide) |
| 9. | Deep Blue | CoO (Cobalt oxide) |
| 10. | Yellow | Fe2O3 (Ferric oxide) |
| 11. | Violet | MnO (Manganese Oxide) |