|Monthly Tech-Tip |
Traditionally we have made GBMF test balls of non-plastic materials using Veegum as the binder. However Veegum interacts with the material enough to affect melting. Psyllium is easily accessible and works much better as a binder (even the flaky version). In this picture, 30g powder, 0.75g psyllium and 20 water are being mixed (some frits only need 15 water, others more). The procedure that seems to work best is to shake the frit/psyllium mix in a bag, pour it into a bowl and pour in 3/4 of the water. Then stir with a spoon. It should liquify quickly, the psyllium seems to help in wetting of the material particles. Within about 30 seconds it should thicken rapidly. With the right amount of water the thickened material will have a Play-Doh consistency and is easily kneaded with your hands. It is very cohesive and almost completely non-sticky, everything in the bowl can be blotted out. Finally, weigh the mass, divide that weight by 3 and weigh out three balls of that weight. If there is enough water you will be able to roll each round between your hands and the pieces will stick together. You might think that cornstarch will also work but no, it does not gel like this and the mix is not plastic either. This works better than Veegum also, it is not as sticky and it is much easier to stir the water into the powder mix.
Glaze Melt Fluidity - Ball Test
A test where a 10-gram ball of dried glaze is fired on a porcelain tile to study its melt flow, surface character, bubble retention and surface tension.
Binders are glues that harden ceramic powders as they dry. They enable improved surface adherence. And slower drying.