When gloss white glaze is crossed over black glaze in reduction firing, it creates this web-like pattern of white. I had seen others creating this effect and liked it. So, I tried it myself. The web-like pattern didn't come out as dense as I wanted, which suggests I need a thicker layer of white glaze over the black.
Firing: Reduction high fire
Clay: Soldate
Made with glazes at Echo Ceramics