Dough color (printing technique)
Dough colors are colors that contain a residual proportion of approx. 20% water. That is why they are particularly suitable for the production of colored paper .
Manufacturing
For the production, aluminum sulfate blocks are first dissolved in a dissolving container (wooden tub) with the help of steam. This solution is then placed in an 8 m³ wooden tub together with Blankfix ( barium sulfate ). Adding small amounts of caustic soda creates a blankfix aluminum hydroxide mixture.
Reaction equation: BaSO 4 + 6 NaOH + Al 2 (SO 4 ) 3 reacts to BaSO 4 + 2 Al (OH) 3 + 3 Na 2 SO 4
Now the water-soluble dyes are dissolved with barium chloride in the dissolving container, added to the large wooden tub and stirred. The result is dough color. The barium chloride serves to bind the soluble dyes to the aluminum hydroxide by lacquering . An insoluble color precipitate forms, which can be easily filtered . Finally the product is filtered in a filter press . It is now ready to be packed in plywood barrels and sold.
use
Dough colors are mainly used for the production of colored paper because they do not form lumps due to their remaining water content and especially because they are non-toxic if the appropriate colorants are used.