|Monthly Tech-Tip |
Left is G3933G1, an Alberta Slip based glaze. Right is Amaco PC-32, Albany Slip Brown. The difference is that they are adding lithium carbonate to supercharge the melting of this type of glaze, which makes it reactive - where thick in the recesses it crystallizes to a much lighter color. Where thin it amplifies the brown body color. The use of the lithium explains why this particular product is more expensive ($2 at time of writing). At current lithium carbonate costs that would cover 6-8% they are adding.
Left is G3933G1, it is part of a project to create an Alberta Slip and Ravenscrag Slip versions of our G3933A recipe (repeated issues with crawling was the motivation). During the process the silky matte texture was lost and thus the opportunity to add lithium. The glaze on the mug on the right, G3933G1, it the same except for the addition of 6% lithium carbonate. Lithium is a super powerful melter, turning this into a very reactive glaze! Our current lithium price is about 15 cents/g. To make a 500ml jar of this would require 330g of powder, at 6% 20g of lithium would be needed. That is $3.
A powerful melter very valuable in ceramic glazes. It is 40% Li2O and has an LOI of 60% (lost as CO2 on firing). This material in now incredibly expensive.