|Monthly Tech-Tip |
This is G1916Q3 low-temperature transparent glaze (it is the G1916Q recipe plus 10% 45-micron silica). Silica is a highly refractory material, this low-temperature glaze should not have been able to dissolve that much of an addition without cost to the gloss, melt fluidity or transparency. But none of these has happened and the reason is, in good part, because of the finer particle size of the silica powder: 45 microns (or 325 mesh). It is applied fairly thick and is runny enough to have pooled at the base. And it is still ultra glossy. A big benefit of the silica being present and having dissolved so well in the melt well is an almost certain increase in the durability and hardness of the glaze. Another benefit is a reduction in the thermal expansion, that is proven by the glaze shivering off the rim (on the far right). This body is Plainsman L215. So, while not suitable on this body, this glaze is ready to be used on others that craze the parent G1916Q recipe. And it has a thermal expansion adjustable recipe, a base frit and about 15% each of a low and high expansion frit. That means some high-expansion Ferro frit 3110 can be introduced at the expense of low expansion Ferro frit 3249.
On the left is the oversize from 100 grams of 45 micron US Silica (325 mesh): 3 grams.
On the right is the oversize from 100 grams of their 95 micron grade (200 mesh): 26 grams!
Clearly, if you want minus 200 mesh material, the #45 325 mesh grade is the one to actually use.
Silica, sold as a white powder, is pure quartz mineral. Quartz is the most abundant mineral, it is pure SiO2 silicon dioxide.