Alternate Names: Frit CC257
|If this formula is not unified correctly please contact us.|
|COLE - Co-efficient of Linear Expansion||6.8|
|GSPT - Frit Softening Point||1700F|
A fritted source of barium for cone 06-1. No longer produced but still sold by Laguna Clay in 2014. Use Ferro FB-284 instead.
According to our tests this analysis appears to be very wrong, the material melts much more than this chemistry suggests.
Essentially an alkaline-earth aluminum silicate. The formula of this frit is not published however we got it from Val Cushing's Notebook. Ferro says to use it with Frit CC-265 for satin effects.
Ferro's instructions were:
First determine the percent BaO in the glaze (% barium carbonate times 0.777), then divide that figure by 0.378 to determine the amount of frit necessary to supply that amount of BaO. [Example: assume 12% barium carbonate; X 0.777 - 9.324% BaO, / 0.378 = 24.67 parts CC257-2 to supply the equivalent amount of BaO as 12% barium carbonate.] Then, reduce the alumina and silica in the glaze by the extra percentage of frit used (24.67 - 12, = 12.67), in the ratio of approximately 1 alumina : 4 silica.
CaO less than 5%
ZrO2 less than 5%
TiO2 less than 5%
Coefficient of expansion (calculated): 8.24 x 10-6
Coefficient of expansion (measured): 6.8 x 10-6
Frit Fusion: 1700F
Empirical Silica:Alumina ratio: 14.07
CAS Number: 65997-18-4
Left: G2934 magnesia cone 6 matte (sold by Plainsman Clays). Right (G2934D): The same glaze, but with 0.4 molar of BaO (from Ferro Frit CC-257) substituted for the 0.4 MgO it had. The MgO is the mechanism of the matte effect. Barium also creates mattes, but only if the chemistry of the host glaze and the temperature are right. In addition, barium mattes are normally made using the raw carbonate form, not a frit. In fritted form, barium can be a powerful flux when well dissolved in the melt and boron is present. This glaze is actually remarkably transparent. However, if this was fired lower it could very well matte.
Out Bound Links
Fusion Frit F403
Overview of strategies in dealing with the hazards of difficult-to-replace barium carbonate in ceramics
Frit 284M, FB284M, FB284-M, FB-284M
In Bound Links
Barium Carb, Witherite