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These stains provide the opportunity to produce a wide range of personalized colours of underglazes. They have been specially processed with underglaze application in mind. They are intended for functional and decorative ware and they can be applied to porous earthenware, vitrified tableware, china and stoneware. Certain colours are also stable up to the high fire conventional porcelain temperature of 1400°C.
As a guide to their mixing characteristics, the colours have been separated into three groups:-
Group 1 - General mixing group
Group 2 - Tin based group
Group 3 - Chromium based group
We recommend the use of Walker Ceramics Brushing Medium (Product Code CB80) for mixing with these powders. It has been formulated so that the colour may be applied to greenware and clear glaze can be applied directly over the decoration.
Group 1
These powders are completely intermixable, in that blends can be produced from within the group, as well as cross blended with Groups 2 & 3. Group 1 colours are made up of a selection of conventional zircon colours, cadmium Zircon inclusion colours, cobalt silicates, aluminates and lead antimoniates. All the colours are chemically compatible and in most cases they have good firing stability.
Group 2
This group of colours is intermixable with Group 1, but not with Group 3. The general rule is not to mix colours containing chrome with tin based colours. Chemical interaction can result in pink discolouration. The tin based colours have a greater importance as underglaze colours than would be expected from them as glaze stains. The Group 2 colours can exhibit better glaze compatibility than their zircon based equivalents. 
Group 3
This group is intermixable with Group 1 but not with Group 2. The colour have limited intermixablity within the group itself. The green and blue green section can be blended within themselves, although it would not be recommended that the green/blue-green section was intermixed with the browns. That kind of combination can cause some instability. Under differing glazes, either the brown or the green could dominate, thus giving colour variation.