Bister is a powder that creates an antiqued effect when mixed with water.
How to use bister powder :
Take an empty (spray) bottle (app. 100ml) and fill it with water. Add a teaspoon of bister powder, put the lid on the bottle and shake well. Poor the mixture through a very fine sieve if there are some granules left. If you need to preserve the mixture for a while, it is best to use distilled water. Use the spray as described in the instructions for the ready made bister.
For a lighter result, add more water to the mixture or directly onto the piece. To intensify the colour, add a few granules of bister onto the piece and spread well with a brush.