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Ferro Frit CC-257

Alternate Names: Frit CC257

Description: High Barium Frit

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% -
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

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.

Various frits fired at 1950F

These sixteen GBMF test balls have melted down onto a slab of grogged clay. Kiln fired at 108F/hr for the last 100 degrees F and held for 15 minutes. This demonstrates the comparison value of this test and how various frits compare in their melting character.

Frits fired to 2050F

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

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.

At 1700F the fast fire frits show an important difference

12 frits melting at 1700F

These were 10g balls melted using our GBMF test, the tile they are being fired on is a grogged stoneware clay. A few of the more interesting ones here are frit 3470 lead zinc, 3185 super high boron, CC257 high barium, FR003 high alkali and F49 and FR001 opacifieds. Notice how early and vigorously some are melting. But notice 557 and 556, they aren’t doing anything - that is not by accident. These are fast-fire frits, they are designed to melt later and more quickly. This is only 1700F, since no one fires this low it makes sense that if a glaze has not started melting it will be able to pass escaping gases of decomposition. This avoids the bubbles and surface defects these cause, as 3185, CC257 and 3470 are already demonstrating. What about FR002, FR002 and 3565, they are melting and look fine? They have higher surface tension and much less contact with the body generating the gases.


Materials Fusion Frit F-403
For ceramic glazes this is a higher quality and safer source of BaO than barium carbonate. It contains 35% BaO.
Materials Frit
Frits are made by melting mixes of raw materials, quenching the melt in water, grinding the pebbles into a powder. Frits have chemistries raw materials cannot.
Materials Barium Carbonate
A pure source of BaO for ceramic glazes. This is 77% BaO and has an LOI of 23% (lost at CO2 on firing).
Materials Ferro Frit FB-284-M
Materials Ferro Frit CC-257-2
Hazards Barium Carbonate
Typecodes Frit
A frit is the powdered form a man-made glass. Frits are premelted, then ground to a glass. They have tightly controlled chemistries, they are available for glazes of all types.
Typecodes Available from Laguna Clays


Co-efficient of Linear Expansion 6.8
Frit Softening Point 1700F
By Tony Hansen
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