Alberta Slip Ravenscrag Slip Textured Engobe G2934 Matte Cone 6 Base Glaze G2926B Cone 6 Transparent Whiteware Base Glaze GA6-A Alberta Slip Cone 6 Base Glaze G2916F Transparent Cone 6 Stoneware Glaze L3954B Mid Temperature Engobe Zero3 K Transparent Glaze Zero3 Engobe G1947U Cone 10 Transparent Glaze G2571A Cone 10 Dolomite Matte Glaze GR10-A Ravenscrag Cone 10R Base Glaze
GA6-A Alberta Slip Cone 6 Base Glaze
The base cone 6 glaze recipe for Alberta Slip, it adds 20% frit to produce a well-melted amber transparent. It is very useful itself as a cover and liner glaze and can become much more if slow cooled (to form surface crystallization) and with additions (e.g. to form cobalt-free floating blue).
Transparent glaze of choice for dark bodies
The amber color and micro-bubble-free matrix make this work so well.
Clear glazes often do not work on dark bodies. The center mug is clear-glazed with G2926B (and is full of bubble clouds). This dark body (M390) is exposed inside and out (the other two mugs have a white engobe inside and midway down the outside). G2926B is an early-melter (starting around cone 02) so it is susceptible to dark-burning bodies that generate more gases of decomposition. Left mug: The outside glaze adds 4% iron to G2926B (the glaze was not screened, so iron particles are agglomerated and acting as a fining agent, removing the bubbles). Right mug: The whole thing is glazed with GA6-A Alberta Slip base glaze (but using Ferro Frit 3195 instead of 3134). These amber glazes have an added benefit: The color darkens over dark burning bodies (to almost black).
Coffee Clay fired at cone 6 with transparent glazes. The Alberta Slip GA6-A glaze (left) is clearly better that the G2926B on the right. This firing is schedule C6DHSC, a 100F/hr slow cool to 1400F. The glaze is the right certainly has fewer bubbles than normal, but still is not nearly as good as the one on the left.
It is standard practice to fire cone 6 using a hold (or soak) at top temperature schedule (e.g. for 30 minutes) to produce a defect-free glaze. However we recommend a drop-and-hold firing schedule (like PLC6DS). Both require manual programming of your kiln (because none of the built-in programs do any kind of hold). If you have not manually programmed your kiln, this is a barrier you need to cross to produce more defect-free glaze surfaces.
The GA6-A glaze on the insides of these mugs has crystallized during cooling (normally it is a transparent amber). This happened because we programmed the firing to drop at 150F/hr down to 1400F (the GA6-C blue requires it). You can prevent the crystallization during slow cooling by adding 1% tin oxide to the recipe.
You can find the home page for this recipe at digitalfire.com by clicking the following: GA6-A. And the cone 6 glaze page at http://albertaslip.com has all kinds of variations (additions of colors, variegators, opacifiers) that can be made.
Alberta Slip as a celadon at cone 6 (left), cone 10R (right). The left recipe is just the base GA6-A with Frit 3195 on Plainsman M370. The other is Alberta Slip/Ravenscrag Slip 50:50 mix on Plainsman P700.
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|Plainsman Clays Ltd.|
702 Wood Street, Medicine Hat, Alberta T1A 1E9
Phone: 403-527-8535 FAX:403-527-7508