G2934 (lower-LOI)

Code: G2934Y
Modification Date: 2019-12-18 13:10:24

Ferro Frit 324910.0
Nepheline Syenite10.5
Calcined Kaolin10.5


This is an "MgO matte". High MgO content is a common matting mechanism at cone 10 but also works at cone 6. This recipe has the same chemistry as G2934, however it sources the MgO from a frit and talc rather than from dolomite. The frit has a predictable chemistry, produces a much lower LOI (3.8 vs. 13.6), a smoother fired surface and better melt fluidity to host stains (stains look fantastic in this base).

WARNING: Like the original, the degree-of-matteness is very dependent on cooling rate. Fast cooling (e.g. free-fall in a lightly-loaded or smaller kiln) produces a silky matte surface. Slower cooling (e.g. a heavily loaded kiln) produces a matter and drier surface (subject to cutlery marking). Test in your circumstances to decide whether to adjust your firing to accommodate this or blend in some glossy G2926B produce the silky surface.

Fusion Frit F-69 can be used instead of Ferro Frit 3249 (actually, it is better). This recipe employs a mix of calcined and raw kaolin to keep the drying shrinkage down (to avoid cracking on drying). If you use pure kaolin it will likely crack during drying. If you do not have calcined kaolin just make your own (bisque fire a container of powder).

This glaze has a very low thermal expansion and will not craze an any common clay body. It accepts stains exceptionally well.

We recommend doing cutlery marking tests on your ware. If they mark, blend in a little transparent glossy glaze (like G2926B). This will compromise the matteness a little but will reduce the marking.

Again, although matte in appearance, this glaze has a high melt fluidity. That means that brush-on colors could bleed.

Because this contains both calcined and raw kaolins you can adjust their ratios to control the compromise between dry hardness and drying shrinkage. If better gelling response to Epsom salts (or other flocculant) is needed trade one or two percent raw kaolin for bentonite (to increase the particle surface area).

1100 water, 1000 powder to get creamy mix.
Regular 2934 (with dolomite) took more water, about 1300. Nicer surface than G2934, same matteness, better fluidity.

Joe: April 29/19 Mixed up a batch and added 10% Mason #6021 Red stain. Final totals were:
G2934Y + 10% stain weighed 5045 grams.
Water weighed 5450 grams.
Let glaze sit for 3 days to saturate before adding final water to bring to a S.G. of 1.43 and viscosity was approx. 12 seconds with ford cup.
At these quantities, the final ratios would be:
Glaze powder (including stain) 48%
Water 52%
This mixture yielded about 7.3 litres of mixed glaze. This glaze was screened 80 mesh and has no Epsom salts added.

Out Bound Links

In Bound Links

XML to Paste Into Insight

<?xml version="1.0"?>
<recipes version="1.0" encoding="UTF-8">
<recipe name="Cone 6 Magnesia Matte Low LOI Version" keywords="The same chemistry as the widely used G2934 but the MgO is sourced from a frit and talc instead of dolomite" id="135" date="2019-04-10" codenum="G2934Y">
<recipeline material="Ferro Frit 3249" amount="10.000" added="0"/>
<recipeline material="Nepheline Syenite" amount="10.500" added="0"/>
<recipeline material="Wollastonite" amount="21.500" added="0"/>
<recipeline material="Talc" amount="14.000" added="0"/>
<recipeline material="EPK" amount="20.500" added="0"/>
<recipeline material="Silica" amount="13.000" added="0"/>
<recipeline material="Calcined Kaolin" amount="10.500" added="0"/>
<url url="https://digitalfire.com/4sight/recipes/cone_6_magnesia_matte_low_loi_version_135.html" descrip="Recipe page at digitalfire.com"/>

By Tony Hansen

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