This was originally developed during the early 1980s to demonstrate principles of glaze chemistry in creating a glaze base sympathetic to the development of chrome-tin pinks and maroons. Articles a videos about this were used as selling tools for Digitalfire Insight software.
This recipe was developed over the years and had many versions. We now recommend G2926B as a base instead.
Related Information
If your glaze can handle more silica and melt just as well then add it!
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The cone 6G1214M glaze on the left melts well. Can it benefit from a silica addition? Yes. The right adds 20% yet still melts as well, covers better, is more glossy, more resistant to leaching, harder and has a lower thermal expansion.
G1214M, W, N, O and S with Mason stains
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This shows clearly how well the M version works with a chrome-tin stain compared to the others. However the 6100 brown stain works best in the N recipe (which have MgO). Notice also that the M has a higher thermal expansion than the others.
Ravenscrag oatmeal layered over black at cone 6
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Ravenscrag Cone 6 GR6-H Oatmeal over 5x20 cone 6 black
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The black recipe was made using G1214M with 5% Mason 6666 stain. The oatmeal overlayer is 50% the thickness of the black. The more fluid under-black comes through leaving islands and vertical rivulets of the stiffer oatmeal. Good control of the glazing process is needed to get consistent results using this approach.
5x20 glaze used as a base for an overglaze
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The blue second layer here is 5x20 cone 6 clear with 2% cobalt oxide and 5% rutile. The base black glaze is 5x20 with 4% Mason 6666 stain.
Cone 6 black with a second layer of oatmeal glaze
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The underglaze is G1214Mcone 6 black (adds 5% Mason 6666 black stain). Overglaze left: GR6-HRavenscrag Oatmeal. Overglaze right: GA6-FAlberta Slip oatmeal. Both produce a very pleasant silky matte texture (the right being the best). Both layers are fairly thin. In production it would be best to spray the second layer, keeping it as thin as possible. It is also necessary to adjust the ratio of raw to roasted Alberta or Ravenscrag Slips to establish a balance between drying hardness but not too much drying shrinkage (and resultant cracking).
Stains that work better in some glazes and not others
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This demonstrates how the host glaze affects the color development of certain stains. Blue is stable in pretty well all glazes. But chrome tin pink (top row) is very particular that the glaze have the right chemistry (1214M is obviously best, it has the highest CaO and lowest B2O3). The 6100 brown works much better in the N and O base glazes (they have higher Al2O3). Stain companies have guidance on chemistry particulars and you can view the chemistry of your recipe in your account at insight-live.com.
G1214Z Cone 6 matte glaze 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.
Transparent Glaze Recipe Transparent recipes can be difficult to develop because entrained bubbles, crystals and crazing are not hidden by color and opacity. In addition, they must be well melted to give good results. Generally transparent recipes are sought after as liner glazes or bases to which to add opacifiers and colors. Typically work is required to match a transparent glaze to a specific clay body.
Glossary
Silica:Alumina Ratio A formula ratio used to evaluate and predict firing properties in ceramic glazes.
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XML to Paste Into Insight-live
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