Testing Underglazes

I wanted to test what effect different firing temperatures have on my underglazes. So, here I've painted a swatch of colours on tiles of porcelain paperclay and covered them with a clear glaze. The left shows the colours pre-glazing. On the right are the tiles after firing. Even though in the earthenware firing the colours are brighter, especially the reds and yellows, I was pleased to see that the colours remained quite true at stoneware temperatures.