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Ravenscrag Cone 10R Dolomite Matte

Code: GR10-J
Modification Date: 2016-09-30 22:50:23
Member of Group: RV10

Plainsman Cone 10R Ravenscrag Slip based glaze. It can be found among others at http://ravenscrag.com.

MaterialAmount
Ravenscrag Slip51.6
Dolomite12.1
Talc2.6
Boraq 5 (Gerstley Borate sub)4.0
Calcined Kaolin13.5
Custer Feldspar16.2
 100.00  

Notes

This is the classic cone 10 reduction silky white matte, its feel, beauty and utility are very difficult to match in any other system. Unlike many feldspar saturated dolomite mattes in use, this one does not craze on stonewares and it does not cutlery mark or stain.

This glaze was developed from the popular G2571A, it has the same chemistry however it sources that chemistry from a completely different recipe based on Ravenscrag Slip (this is a good example of how Insight ceramic chemistry software can be used). The pleasant silky surface is almost identical (though slightly darker in color due to a little higher iron content). Add a little zircopax (e.g. 3-5%) to whiten the color if you desire or if you need to precisely match the G2571A. This glaze has the characteristic superb application and suspending properties of Ravenscrag Slip glazes.

Note that the calcined kaolin is important. If you use raw kaolin, the glaze will shrink too much during drying. For a slip glaze, raw kaolin would be OK. If you do not have the Boraq (Gerstley Borate substitute) then you can substitute real Gerstley Borate or another equivalent.

The two most common variations are bamboo and robin's egg blue (see photos here).

Mar 2015: We have found a tendency for this glaze to craze on some stonewares after decal firings. See the linked picture.

Two great dolomite matte cone 10R recipes on iron stoneware

Two great dolomite matte cone 10R recipes on iron stoneware

GR10-J Ravenscrag silky matte (right) and G2571A matte (left) on a dark burning iron speckled stoneware at cone 10R. Surfaces have identical feel (the chemistries are very close). The former fires a little darker color because of the iron contributed by the Ravenscrag Slip.

A refined-material cone 10R dolomite matte (left) vs. one made using Ravenscrag Slip

A refined-material cone 10R dolomite matte (left) vs. one made using Ravenscrag Slip

GR10-J Ravenscrag silky matte (right) and G2571A matte (left) on a buff stoneware at cone 10R. Surfaces feel identical, the slightly darker color is due to iron content in the Ravenscrag. The former was formulated to mimic the latter using as much Ravenscrag Slip as possible yet still maintain the same chemistry.

A refined-material cone 10R dolomite matte (left) vs. one made using Ravenscrag Slip

Robin's egg blue at Cone 10R: add 1% cobalt oxide and 0.2% chrome oxide to GR10-J Ravenscrag silky matte. Does not work well on porcelains (left), very well on buff stonewares (right). Inside of center mug is GR10-J.

How to turn a dolomite matte white glaze into a bamboo matte

How to turn a dolomite matte white glaze into a bamboo matte

Make cone 10R bamboo colors using the GR10-J Ravenscrag silky matte base recipe (right) and adding 1% iron (left), (0.5% centre). These samples are porcelain. This iron addition also works using the G2571A matte base recipe.

Ravenscrag GR10-J Cone 10R Bamboo glaze variation

Ravenscrag GR10-J Cone 10R Bamboo glaze variation

Porcelain (left), buff stoneware (center), iron stoneware (right). Works well on all body types. On porcelain, interesting red tones and variations in tone appear.

Bamboo glaze that is actually functional

Bamboo glaze that is actually functional

The stunning cone 10R Ravenscrag bamboo glaze (GR10-J plus 0.5% iron oxide) on a Grolleg porcelain. Up close it can feel and look like a fine wood surface (when used on a porcelain). The cone 10 recipes page at Ravenscrag.com has more info.

Ravenscrag dolomite matte

Ravenscrag dolomite matte

GR10-J Ravenscrag dolomite matte base glaze at cone 10R on Plainsman H443 iron speckled clay. This recipe was created by starting with the popular G2571 base recipe (googleable) and calculating a mix of materials having the maximum possible Ravenscrag Slip percentage. The resultant glaze has the same excellent surface properties (resistance to staining and cutlery marking) but has even better application and working properties. It is a little more tan in color because of the iron content of Ravenscrag Slip (see ravenscrag.com).

Why did this piece came out of a decal firing crazed?

Why did this piece came out of a decal firing crazed?

This Cone 10 matte mug has been refired to attach decals. During the refire the Quartz-containing body passed up through quartz and cristobalite inversions while the glaze did not (all of its quartz was converted to silicates during the previous glaze firing). The sudden expansion in these two zones stretched the glaze and cracked it. Had that glaze been better fitted (under some compression) it would have been able to survive.

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By Tony Hansen

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