Underglaze painting looks straightforward until you try to mix two colours and end up with something that resembles a grey puddle. The good news is that the problem is almost always technique rather than colour sense. Underglaze pigments behave differently from watercolour or acrylic, and understanding a few basic principles makes the layering process much more reliable.
Why underglaze does not mix the way paint does ¶
Underglaze is a pigment suspended in a clay slip, and when it dries on bisqueware it becomes slightly chalky. If you apply a second colour before the first is fully dry, the two layers blend at the surface and the result is often muddy. The standard approach is to apply the first layer, wait two to three minutes until the sheen disappears, then apply the second. At that point the first layer is dry enough to hold its colour.
Loading the brush correctly ¶
A brush loaded too heavily will drag across the bisqueware surface and deposit colour unevenly. The standard test is to draw the loaded brush across a practice tile: if the stroke is even and opaque after one pass, the load is right. If it beads or pools at the edges, thin the underglaze slightly with a few drops of water and test again. At Willow Panel Gate we keep a set of practice tiles at each table for exactly this reason.
Building depth with three layers ¶
The most reliable way to achieve a sense of depth is to work in three thin layers rather than one thick application. The first layer is a diluted wash that tints the surface. The second, applied when the first is dry, is full-strength and defines the main shape. The third is selective, applied only to the shadow areas or to reinforce the darkest tones. Three layers of the same colour produce a depth that a single heavy application cannot.
Where the liner tool changes everything ¶
For fine lines and detail work, a liner tool loaded with underglaze gives you a line weight that a standard brush cannot. The key is to keep the underglaze in the liner on the thicker side, because the narrow nib evaporates moisture quickly. If the line breaks up mid-stroke, add a small amount of water to the pot and stir. Liner work is best done after the base colour layers are fully dry, so you are drawing on a stable surface.
What happens to your colours in the kiln ¶
Underglaze colours shift during firing. Blues tend to deepen, yellows sometimes pale slightly, and the iron-oxide grey we keep on our palette darkens considerably. We give every visitor a fired colour sample card at the start of their session so they can see the fired result of each colour before committing. Layering two colours that both shift in the same direction tends to produce more predictable results than combining a colour that intensifies with one that fades.
Layering underglaze is a skill that develops quickly with practice. Most visitors are producing noticeably better results in their second session than their first. If you want to develop a more consistent approach, the private Thursday morning session gives you three hours and direct guidance from Natsuki Igarashi.