|Monthly Tech-Tip |
This is the dolomite body recipe L4410P. In the plastic form we have measured it’s drying shrinkage at 6%. It has no firing shrinkage at cone 04. The final size needed is 20.5 cm. Thus I calculated the cut size to be 20.5 / (100 - 0.06) = 21.8 cm (or 20.5 / 0.94 = 21.8 cm). Sure enough, this 21.8 cm square dried and shrunk down to 20.5. To keep these flat we put them between sheets of drywall, the process takes 2-3 days. As noted, during firing no change in size occurs.
Plainsman Snow clay (developed under code number L4410P) makes this QRCode mosaic possible. Each 8mm square porcelain pixel is glaze-glued onto a 21cm square 5mm thick ceramic tile made of Snow (simply rolled and cut and dewatered between sheets of Gyproc). During the bisque firing to cone 04, the Snow tile had zero shrinkage, from dry to fired, and therefore did not curl up at the edges. On refiring to melt the glaze it again stays flat. No other common plastic clay can do this! Snow continues this zero-shrinkage performance for seven more cones of firing (all the way to 4). The secret is the 40% dolomite it contains. We silicone-sealed this work front and back, now it is ready for outdoor installation.
Tile manufacture is the largest sector of ceramic industry. Engineers overcome the very difficult technical challenges of drying and firing defect-free, flat and durable tile. Potters can do it too.