Modification Date: 2016-03-17 13:09:41
This glaze was born as a demonstration of how to use chemistry to convert a glossy cone 6 glaze into a matte.
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Please click the article link below for more information.
This recipe is adjustable in that you can raise and lower the silica to increase and decrease the gloss or matteness.
However, the spirit of this recipe is not to present the perfect matte, it is to demonstrate about how Al2O3:SiO2 chemistry balance in a glaze recipe can be changed to adjust the degree of matteness of a glaze (for an article on this subject). Generally the best mattes are made using high MgO levels in an otherwise correctly melted base (see linked article). You should consider testing the G2934 recipe in preference to this one.
G1214Z blue glaze from Lilly Ann Hume
G1214Z golden glaze sample from Lilly Ann Hume
G1214Z with overglaze decoration painted overtop
1214Z over Ravenscrag slip at cone 6 gives mottled surface
These are two cone 6 matte glazes (shown side by side in an account at Insight-live). G1214Z is high calcium and a high silica:alumina ratio (you can find more about it by googling 1214Z). It crystallizes during cooling to make the matte effect and the degree of matteness is adjustable by trimming the silica content (but notice how much it runs). The G2928C has high MgO and it produces the classic silky matte by micro-wrinkling the surface, its matteness is adjustable by trimming the calcined kaolin. CaO is a standard oxide that is in almost all glazes, 0.4 is not high for it. But you would never normally see more than 0.3 of MgO in a cone 6 glaze (if you do it will likely be unstable). The G2928C also has 5% tin, if that was not there it would be darker than the other one because Ravenscrag Slip has a little iron. This was made by recalculating the Moore's Matte recipe to use as much Ravenscrag Slip as possible yet keep the overall chemistry the same. This glaze actually has texture like a dolomite matte at cone 10R, it is great. And it has wonderful application properties. And it does not craze, on Plainsman M370 (it even survived and 300F to ice water plunge without cracking). This looks like it could be a great liner glaze.
True functional mattes have fluid melts, like glossy glazes. They need this in order to develop a hard, non-scratching durable glass. The mechanism of the matte on the right is high Al2O3 (G1214Z), it is actually melting more than the glossy glaze on the left (G1214W).
A melt fluidity comparison between two cone 6 matte glazes. G2934 is an MgO saturated boron fluxed glaze that melts to the right degree, forms a good glass, has a low thermal expansion, resists leaching and does not cutlery mark. G2000 is a much-trafficked cone 6 recipe, it is fluxed by zinc to produce a surface mesh of micro-crystals that not only mattes but also opacifies the glaze. But it forms a poor glass, runs too much, cutlery marks badly, stains easily, crazes and is likely not food safe! The G2934 recipe is google-searchable and a good demonstration of how the high-MgO matte mechanism (from talc) creates a silky surface at cone 6 oxidation the same as it does at cone 10 reduction (from dolomite). However it does need a tin or zircon addition to be white.
Out Bound Links
This glaze was developed using the 1214W glossy as a starting point. This article overviews the types of matte glazes and rationalizes the method used to make this one.
Takes you on a detailed tour of how to start with a glossy glaze, compare its chemistry with a target formula in the light of what kind of chemistry matte glazes have, then alter the chemistry while a...
A glaze that is not glossy. Of course, unmelted glazes will not be glossy, but to be a true matte a glaze must be melted and still not glossy. To be a functional matte it must also resist cultery marking, clean well and not leach into food and drink. Thus it is not easy to make a good matte glaze. I...
A base MgO matte glaze recipe fires to a hard utilitarian surface and has very good working properties. Blend in the glossy if it is too matte.
2014-03-26 - This glaze is a cone 6 dolomite matte. It is the product of a series of tests to determine the best levels of SiO2 and Al2O3 in a boron fluxed (but no...
In Bound Links
This is a base transparent glaze recipe developed for cone 6. It is known as the 20x5 or 20 by 5 recipe. It is a simple 5 material at 20% each mix and it makes a good home base from which to rationalize adjustments.
The process we used to improve the 20x5 base cone 6 glaze recipe
A recipe developed by Tony Hansen in the 1980s. Its was popular because of the simplicity of the recipe and how well it worked with chrome-tin stains.
2003-12-17 - This is also known as the 20x5 recipe. It was developed during the early 1980s to demonstrate principles of glaze chemistry in creating a glaze base s...
Substitute for low expansion cone 6 G1215U, this sources MgO from talc instead of a frit
2013-05-29 - During 2013 we saw problems with the G1215U low expansion glossy that we had been recommending from some years. It was not melting to a completely ult...
Plainsman Cone 6 Ravenscrag Slip based glaze. It can be found among others at http://ravenscrag.com.
2014-02-20 - This works well on Plainsman M340, but especially on a whiteware like M370. Produces an ivory white with some fleck. The surface is very silky, remini...
By Tony Hansen+