|If this formula is not unified correctly please contact us.|
|COLE - Co-efficient of Linear Expansion||7.1 x 10-6|
|GSPT - Frit Softening Point||880-1050C M|
This term refers to frits having approximately one molar part of lead and two of silica. This ratio of silica and lead produces a stable low solubility powdered glass material that can be used in production with relative safety to workers. Of course it can be put into a recipe of unbalanced chemistry to create a glaze that is leachable.
Many lead bisilicate frits contain from 1-3% Al2O3 and are referred to as "lead alumina bilsilicates". This addition further stabilizes the frit glass powder itself (and prevents phase separation is the glass during firing).
Many manufacturers used to make this frit formula. But today, especially in North America, it is difficult to find a source. While available in some places, they only sell to manufacturers (not to potters, schools or hobbyists). Ceraflux from Hammond Lead Products might be the best choice.
For certain glazes care must be taken not to ball-mill these frits too fine (eg. tin glazed earthenware). Some products are dry milled by the manufacturer, others are well milled (much less common).
These cone 04 glazes have the same recipe (a version of Worthington Clear sourcing B2O3 from Ulexite instead of Gerstley borate). While the one on the left is OK, the one on the right is great! Why? It has 10% added lead bisilicate frit. Of course, I would not recommend this, I am just demonstrating how well it melts. Still, we gasp at the thought of using lead while we thrive on unstable flux-deprived, glass-deprived and alumina-deprived base stoneware glazes with additions of toxic colorants like chrome and manganese!
Out Bound Links
Inorganic Lead and Ceramics by Edouard Bastarache
Minium, Lead(II,IV) oxide
In Bound Links
Metallic glazes can most easily be produced in oxidation by mixing a very high percentage of manganese dioxide with a low melting frit. The metallic visual effect is modified by the degree of melting of the glaze, the saturation of metallic oxides in the recipe and the amount of crystallization tha...
The long slow death of lead use in ceramics taught us some lessons. Manufacturers who still use acid tests to determine glaze toxicity risk liability.
Frit 4364, Frit 3531, Frit DA4064
PotteryCrafts Frit 2950
Potclays Lead Bisilicate Frit
Frit 545, Frit P545
P29 Bly-bi-silikat, Frit P29
Lead alumina bisilicate
C1251 Fritte, C 1251 Fritte, Ceradel Frit 1251
C1250 Fritte, C 1250 Fritte, Ceradel Frit 1250
C1249 Fritte, C 1249 Fritte, Ceradel Frit 1249,C-1249
Frit VTR 29, Frit VTR29