I only have Brushos, but can tell you that with them, the initial colour on the label is not all you get.As you add water- or they come into contact with the water on the page, you will start to see other colours appear too.
This sheet had only one blue and one green pot of colours applied, but you can see purple appearing in the blue, and yellows in the green. This is what it looked like when it dried. I got two sheets as I used a second to 'mop up' some of the colour. The one on the right is the 'original', and you can see the purples and yellows clearly.
I have a friend who bought Pixie Powders, and from what I understand, they do not react like this, the colour stays a pure version, rather than separating into individual elements.
Looking at what UndestandBlue says, the Bisters are very similar to another brand we have over here,Infusions, by Paper Artsy. They are also a powder which contain walnut shell granules, and how long you let them stay wet depends how much of the walnut colour shows in the piece.Hth.
BISTERS, BRUSHO'S, PIXIE DUST
