The secret to cool bodies and glazes is alot of testing. But how will you be able to learn from that testing without a good place to store the recipes? Document the successes and failures? Do it in your account at https://insight-live.com.

Cone 6 Silky Matte

Code: G1214Z
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.

MaterialAmountPercent
Wollastonite27.026.2%
Frit 312436.035.0%
EPK35.034.0%
Silica5.04.9%
 103.00  

Firing Schedule

Rate (F)Temp (F)Hold (Min)Step
100220601
300173302
1082175153
1502075304

Notes

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

Compare two glazes having different mechanisms for their matteness

Compare two glazes having different mechanisms for their matteness

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.

A functional matte cone 6 glaze should melt as well as a glossy

A functional matte cone 6 glaze should melt as well as a glossy

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 good matte glaze. A bad matte glaze.

A good matte glaze. A bad matte glaze.

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

In Bound Links


By Tony Hansen

+


Feedback, Suggestions

Your email address

Subject

Your Name

Message


Copyright 2003, 2008, 2015 https://digitalfire.com, All Rights Reserved