Very good info. J-Bay
Like the food coloring idea, shall use it
Now... Im buying off the shelf amaco, velvets stuff like that...barking up the wrong tree there?
Still needa grinda ?
okay Thanks much fellas...
a plan is coming together
Japanese brushwork with cobalt decoration like this is often done directly onto the RAW procelain. Much different consistency from bisqued. Doesn't "suck" the brush dry quite so fast. Try both ways and see what you like. Cobalt pigment is so strong...... if you screw up either on the raw clay or the bisque....... you can't get fully "rid" of it.... and it gets trashed anyway... so not much risk to trying on the raw clay.
I've visited the the Kondo family in Kyoto (their studio near Kyomizudera) and watched the brushwork being done. The grinding is considered an important and integral part of the process.
Also note that cobalt CARBONATE (here in the USA) comes in a finer particle size than cobalt OXIDE. So I'd start there.
I never use commercial underglazes... so can't really say. I ALWAYS use commercial overglaze enamels... and grind them too.