| The soda or German vat is used extensively on the Continent, but has not found much favour with dyers in England. On the whole, it is more easily managed than the woad vat. It is more suitable for light bright shades ; but for dark shades, especially on heavy cloth, the woad vat is to be preferred. The soda vat is prepared with indigo, bran, treacle, madder, sodium carbonate, and lime. |
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The soda vat Delmart gives the following proportions for a vat of 1,800 gallons capacity:
These quantities give a comparatively weak vat. As in the case of woad vat, the proportions of ingredients used by different dyers vary greatly. For a vat of medium strength the Badische Anilin- und Soda-Fabrik recommend the following proportions for synthetic indigo and a 2,000 gallon vat:
In place of the 40 lbs. indigo paste 20 per cent., about 13 to 14 lbs. of 60 per cent. Bengal indigo might be taken. In setting a vat the water is heated to about 65 ºC. and the above ingredients, irrespective of order, added. The vat is well stirred, covered, and allowed to stand for about 24 hours. It is then examined and treated in a similar manner to the woad vat in its preparation. The vat is fed with indigo, treacle, and lime as required, and occasionally, once or twice a week, about 2 lbs. of soda added. Dyeing is conducted in this vat in the same way as in the woad vat. Edmund Knecht, Christopher Rawson, Richard Loewenthal, Manual of dyeing : for the use of practical dyers, manufacturers, students, and all interested in the art of dyeing., 6th ed. (1920), London: Charles Griffin and company, limited; Vol. 1, p. 324 |
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