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Low Expansion Glossy Clear Cone 6

Code: G1215U
Modification Date: 2015-10-30 04:31:44

A recipe sourcing high MgO (from Ferro Frit 3249) to produce a low expansion glass resistant to crazing on lower silica porcelains.

F-4 Feldspar24.024.4%
Ferro Frit 324920.020.3%

Firing Schedule

Rate (F)Temp (F)Hold (Min)Step


The original impetus to create this recipe was to reduce the thermal expansion of the G1214M and G1215W recipes to work better on porcelains (the others craze). Although a clear transparent glaze, the higher MgO content can produce dimples in the surface if fired too quickly. The higher MgO also affects the color response (this glaze does not work with chrome-tin pink and maroon stains).

Keep in mind that you cannot expect one glaze to work well on both porcelain and stonewares. This fires to a very low expansion glass, while good on vitrified porcelains, it may be under too much compression if used on stonewares (for example, if used on the insides of vessels its compression could make the piece brittle and prone to failure, especially when exposed to sudden increases in temperature). G1214W may be a better choice. To know for sure, glaze a piece only on the inside, fire, then drop it on the floor. If it explodes into many many pieces, the glaze is under too much compression.

As of spring 2013 we are altered this recipe to reduce the MgO content and eliminate the expensive frit 3249 (See G1216L and M). This was done because some users experienced a shift toward a silky matte appearance. We were not been able to explain this sudden change, possibly it was due to a change in the frit. However this recipe continue to work for many other people.

Out Bound Links

In Bound Links

XML to Paste Into Insight

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<recipes version="1.0" encoding="UTF-8">
<recipe name="Low Expansion Glossy Clear Cone 6" keywords="A recipe sourcing high MgO (from Ferro Frit 3249) to produce a low expansion glass resistant to crazing on lower silica porcelains." id="45" date="2015-10-30" codenum="G1215U">
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<recipeline material="Silica" amount="26.000" unitabbr="g" conversion="0.0010" added="0"/>
<recipeline material="Wollastonite" amount="14.500" unitabbr="g" conversion="0.0010" added="0"/>
<recipeline material="F-4 Feldspar" amount="24.000" unitabbr="g" conversion="0.0010" added="0"/>
<recipeline material="Ferro Frit 3249" amount="20.000" unitabbr="g" conversion="0.0010" added="0"/>
<url url="" descrip="Recipe page at"/>

By Tony Hansen

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