Dark Blue by Johnson Matthey may be brushed on wet clay, greenware, or on bisque. Underglaze color is suitable for a variety of pottery painting
Underglaze - Wikipedia
Western Underglaze Project Pack
Painting with Underglazes — Rat City Studios
Underglaze Decorating Crayons
Dark Yellow Powder Pigment Underglaze Ceramic Paint - Australia
Ceramic Colorant - Singapore
6 Different Ways to Use Underglazes With Ceramics - The Art of Education University
Rice Bowl Set Underglaze Colored Ceramic Bowls Japanese Hand - Temu
Blue Underglaze