Monthly Tech-Tip from Tony Hansen SignUp

No tracking! No ads!That's why this page loads quickly!

1-9 | A | B | C | D | E | F | Frits | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z

Ferro Frit CC-257

Alternate Names: Frit CC257

Oxide Analysis Formula
BaO 33.80% 0.62
CaO 5.50% 0.28
K2O 0.79% 0.02
MgO 0.31% 0.02
Na2O 1.00% 0.05
SrO 0.57% 0.02
TiO2 2.20% 0.08
Al2O3 9.20% 0.25
SiO2 46.60% 2.18
Fe2O3 0.04% 0.00
Oxide Weight 280.74
Formula Weight 280.74


A fritted source of barium for cone 06-1. No longer produced but still sold by Laguna Clay in 2019. 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.

Approximate Composition:
CaO less than 5%
BaO 37.8
Al2O3 5-25%
SiO2 25-50%
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

Related Information

Various frits fired at 1850F

16 GBMF tests on a slab of grogged clay. Kiln fired at 108F/hr for last 100 degrees F and held for 15 minutes.

Frits fired to 2050F

These are higher temperature frits. 10 gram balls were melted on to this tile.

Various frits fired at 1950F

16 GBMF tests on a slab of grogged clay. Kiln fired at 108F/hr for last 100 degrees F and held for 15 minutes.

Substituting MgO for BaO in a matte will also make a matte, right? Wrong.

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.

1700F Frit Melt-Off 2: Who is the winner?


Materials Fusion Frit F-403
Materials Ferro Frit FB-284-M
Materials Barium Carbonate
Materials Frit
Typecodes Available from Laguna Clays
Typecodes Frit
Hazards Barium Carbonate


Co-efficient of Linear Expansion6.8
Frit Softening Point1700F

By Tony Hansen

Tell Us How to Improve This Page

Or ask a question and we will alter this page to better answer it.

Email Address





Leave the following empty, All Rights Reserved
Privacy Policy