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
Video: Convert a glossy glaze to a calcia matte:
Ten minutes of glaze-chemistry adrenaline!
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Watch the G1214Z video to see me convert the G1214M 20x5 cone 6 clear base into G1214Z cone 6 calcia matte using simple glaze chemistry and recipe logic. This first appeared in the Digitalfiredesktop Insight instruction manual 30 years ago. It is an understatement to say that this process is interesting if you want to know more about glazes, their chemistry and recipe logic. Watch this video and see me adjust the recipe of my high-calcium transparent cone 6 glaze to convert it into a calcia matte. In an Insight-live.com account, the process is easy enough for anyone. We'll cut the Si:Al ratio, increase the CaO, maintain the thermal expansion for glaze fit and make the recipe shrinkage-adjustable using a mix of calcinedkaolin and raw kaolin. We will even compare it with the High Calcium Semimatte from Mastering Glazes.
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.
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.
20x5 Cone 6 glossy black with GR6-H, GA6-F glazes over:
Crawling will happen unless mitigations are taken
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The underglaze is the 20x5 cone 6base transparent glaze (G1214M with 5% Mason 6666 black stain). Overglaze left: GR6-HRavenscrag Oatmeal. Overglaze right: GA6-FAlberta Slip oatmeal. Both produce a pleasant silky matte texture. Double layering using typical dipping glazes is prone to crawling (because of shrinking and cracking during drying). By keeping layers fairly thin, it is possible to achieve success, but with glazes high in clay content (as these are), more is needed. A mix of raw and roasted Alberta and Ravenscrag Slips is the answer here. Start with a 50:50 ratio and adjust to establish a balance between drying hardness and drying shrinkage. For more assurance in production situations, mix the underlayer black as a base-coat dipping glaze.
There are enough variables that a record-keeping system is needed. Start now, and you won't regret it.
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.
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.
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.
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XML to Paste Into Insight-live
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