M-340

M340 is more vitreous than in the past (porosity can go as low as 0.5% at cone 6). This will be a benefit to most users, producing stronger and more functional ware. However, for some susceptible shapes it can mean more warping during firing. Because our 3B native clay became more vitreous in a mining we recently began using, it was necessary to remove all the talc from the M340 recipe. But even that was not enough to bring it into line with the normal target of 1.5% porosity at cone 6. A recipe adjustment is being tested and more information will be coming soon.