This is from the Highwater Clay Website:
The Fall of Frit P25 and the Rise of 3269
Once again an important ceramic material, frit P25, is going by the wayside. It seems as though this has been happening a lot lately! P25 is made by Pemco and they are getting out of the frit business. In anticipation of P25 being unavailable, Highwater Clays will stock Ferro frit 3269 as a replacement.
Unlike feldspar and silica, frits are a manufactured material. Commonly used by industrial ceramics, glass producers and potters alike, frits are comprised of raw materials such as alumina, sodium, silica, potassium, calcium and boron. The raw materials are melted together until vitreous and then ground down to powder form. Each frit has a specific formula and was designed for a specific need. While there are thousands of frits available, potters generally use just a few different types. Their low melting point makes for a valuable melting agent in glazes and promotes fusion to the clay body in underglaze and slip. Certain frits can be used as a low fire glaze all by themselves and some potters even use them as a flux for clay bodies, although that gets a bit pricey. The complex manufacturing process causes frit to be more expensive than other fluxes.
Frit formulations tend to be fairly standard across the industry and most have a readily available substitute. However, there are slight differences in the chemical analysis of P25 and 3269 which could affect the fired quality of a glaze recipe. As always, testing is recommended before firing up a whole glaze load and please contact us if you have any questions.