colouring metal

These 2 recently made planes, the one in the background I coloured yesterday, the one in the foreground I am going to colour today.

These are the colouring agents I use, Perma Blue first, Potassium Sulphate crustals on the right dish. The amount is plenty.

I have applied the Perma Blue with a brush over the bronze and steel in this picture.

Minutes later with a damp cloth, I vigorously rub most of the black off, as shown.

Using the same damp cloth, I dip it in the crystals, These have been crushed with the handle of a chisel.

I then rub with the damp cloth all over the bronze and steel. After about a minute or 2, using a dry cloth I rub over again, removing the film that has formed when dry. This picture shows the damp cloth with the crystals that I used and the results after a few minutes.