We make these using a porcelain containing about 5% Mason 6666 stain. Originally they were made as pixels for making ceramic QRCodes, but they proved valuable for also doing glaze bonding tests. We fire them to vitrify well, this intensifies the black color. The 3D printed template stamps 9x9mm tiny square tiles. We roll the porcelain to 1/8" thickness for stamping. Pressing the cutter down into the clay rounds the top edges and creates a concave underside. An overnight drying provides enough shrinkage that they will drop out of the mold. Before drop-out we press them all further in, this trims excess around the bottom edges.