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Left column is the original, and widely used recipe (with dolomite). Right is the newer version that sources the MgO from talc and a frit instead (with a number of advantages).
Cone 6 Magnesia Matte Base
Auto Unity Formula
This matte recipe was developed at Plainsman Clays. It descends from a high-dolomite recipe that was originally used to compare shipments of dolomite for consistency.
This is a slight variation of the Master recipe wherein the Frit 3124 has been increased, and the Flint Silica quantity is slightly higher.
G2934 Matte vs. LA Matte
LA Matte has been popular for many years. However as seen here, it is not stable in the kiln because it is a zinc matte that depends on crystallization during cooling to create the surface. 2934 is an MgO matte, it is much more stable and has a better surface that does not cutlery mark nearly as bad.
G2934 Matte vs. 2928C Ravenmatte
These two have very similar chemistries. The 2928C uses as much Ravenscrag slip as possible yet still have the same chemistry as the well known Moore's matte recipe. While it appears whiter here, this is because it contains 10% zircon, normally it would be darker because of the iron in Ravenscrag Slip.
G2934 with Hemlock Green, Pansy Purle Stains
10 gram balls have been melt down onto a tile at cone 6.
True mattes should still be matte if overfired
The G2934 is a high-MgO matte, it melts well and does not cutlery mark or stain easily. As evidence that it is a true matte, notice that it is still matte when fired to cone 7 or 8. VC71, while having a similar pleasant silky matte surface at cone 6, converts to a glossy if fired higher (suggesting that its cone 6 matteness is due to incomplete melting). For the same reason the VC71, it is whiter in color (but as soon as it begins to melt and have depth the color darkens).
C6-Cone 6 Glaze
G2934 Cone 6 Matte Low LOI Version
Auto Unity Formula
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 the widely used G2934, however this one sources much of the MgO from a frit and talc rather than from dolomite. The benefits are a much lower LOI (3.8 vs. 13.6), a smoother fired surface and better melt fluidity (while still very matte).
G2934Y plus 8% Cerdec orange stain on Polar Ice, P300
The stain is #239616 encapsulated. The silky surface is stunning. The color is brighter on whiter porcelains.
G2934Y vs. G2934 melt flow balls
10 gram balls were melted down onto these tiles at cone 5.5.
G2934Y vs G2934 melt flow test
The difference is quite amazing. The chemistry is the same. But the MgO is much more readily released from its source materials in the Y version. Also, even thought the melt is more fluid, it is still just as matte. Part of the reason for the extra fluidity could be the much lower entrained micro-bubble population in the Y (these possibly impeding the flow of the dolomite version on the left).
G2934Y matte with Cerdec red, orange stains
8% stain in each. Cone 6. Drop and hold firing. The surface quality is truly stunning!
G2934Y matte on M370 - cup
Surface very pleasant and finer than the standard G2934.
G2934 (left) vs G2934Y (right) at cone 6
G2934Y with brushwork decoration - By Ingeborg Koot
It is not bleeding significantly because the glaze has not been applied too thick.
C6-Cone 6 Glaze
239416 - Yellow
1680 dry and 1400 water produced SG of 1.44. Pretty thick, added a little darvan.
239616 - Orange
Cerdec stain. Required no Epsom salts at 1.43 SG.
4 - Overglaze Blue
Test this as a brush-on color for using over G2934Y. We should demonstrate to customers how to fine tune the melt fluidity of an overglaze color and how to mix it with gum to make it paintable.
6404 - Purple