Sometimes celadon glaze can get these flashes of red.
This was one of the first test plates I made for a custom order of dinner plates. I tried to glaze the bottom side of the plate but it stuck to the kiln shelf because my foot is too small. The large white spot on the back is due to grinding off the glaze that had stuck to the kiln shelf.
Firing: Reduction
Clay: English porcelain
Made with glazes at Echo art studio