Alberta Slip Ravenscrag Slip G2934 Matte Cone 6 Base Glaze G2926B Cone 6 Transparent Whiteware Base Glaze GA6-A/B Alberta Slip Cone 6 Base Glazes GR6-A Ravenscrag Cone 6 Base Glaze L3954B Mid Temperature Engobe Zero3 K Cone 04-02 Transparent Glaze G1947U Cone 10 Transparent Glaze G2571A Cone 10 Dolomite Matte Glaze GR10-A Ravenscrag Cone 10R Base Glaze
G2934 Matte Cone 6 Base Glaze
For Stonewares and Porcelains.
A dolomite silky matte for cone 6. It fires translucent rather than completely transparent (because it is a matte). If you want pure white, add Zircopax (start with 5%, but keep it at a minimum to minimize cutlery marking).
G2934 Cone 6 Matte base (upper left sample) with various stain additions. A porcelain body has been used.
The degree-of-matteness is very dependent on cooling rate. Fast cooling (e.g. free-fall in a lightly-loaded or smaller kiln) produces our desired silky matte surface. Slow cooling (e.g. a heavily loaded kiln) produces a more matte and drier surface (subject to cutlery marking). Do test firings to determine if you can adapt your firing to this recipe or need to adapt this recipe to your firing. If the latter, blend in some glossy G2926B to shine it up to the degree needed.
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.
G2934 matte is an excellent color base and works particularly well with inclusion stains. However, each different color created will likely require fine-tuning the degree of matteness. It is already quite matte, to shine it up slightly by blending in some of our clear glossy base glaze G2926B (click here to see an example).
The recipe of this glaze is not proprietary. We developed it and sell it premixed but you can batch it (or even adjust it) yourself. For detailed technical information check the page for G2934 at the Digitalfire Reference Library.
Adding the Stains and Opacifiers: Simply multiply the weight of the amount of powder you want to use and divide by 100. For example, if you have 2000 grams of glaze powder and want to add 6% stain: 2000*6/100=120 grams of stain. Or, 10% zircopax: 2000*10/100=200 grams of zircopax (stain %'s are suggestions, for some colors you may need more, testing is needed). Bright colors and whites will be muted on dark-burning bodies.
For a one-coat dipping glaze we recommend a specific gravity of 1.43 (to get that multiply the total weight of powder by 1.08 to determine the amount of water). 1 kg of powder should yield about 1.4 litres of liquid glaze. To prepare it for use as a single layer dipping glaze, add the powder to 90% of the water and mix until it flows well. Then adjust the amount of water to get the right specific gravity (more water to lower it). If needed, adjust the viscosity to prepare for sieving through 80 mesh. If the slurry is thin, there is a danger of it settling out while sieving, so it must be gelled. To do that add enough flocculant (vinegar, epsom salts) so that the slurry mass stops motion in about 5 seconds after mixing or stirring is ceased. Flocculants are powerful, only a few drops of vinegar (or pinches of crushed epsom salts) per gallon are needed.
After sieving do a final viscosity adjustment to make the slurry thixotropic (thixotropic liquids gel after motion stops). You can "see" the slurry thixotropy by noting a "bounce-back" on final stop-motion after stirring. Add enough flocculant to get stop-motion in around 2 seconds (in a 1-2 gallon bucket). As before, be careful in adding the flocculant, it is easy to add too much and get a bucket of jelly (if that happens add (by the drop) Darvan to re-thin it). When the slurry is right, you can two-second-dip a piece and on withdrawal it will drain well, gel quickly, only a few drips will fall and on turn-over the glaze will not run back down. It will apply in an even layer on dense or porous bisque. This "rheological state" of the glaze slurry can change on storage so be ready to adjust it later. Recheck the specific gravity from time to time and, if needed, adjust by adding or removing water.
As you gain confidence with doing this you will be able to create a thixotropic slurry at a range of specific gravities. Our recommended specific gravity is based on how much water is needed to get the undeflocculated glaze to a state where it needs about 2 grams of epsom salts per gallon to gel.
This can also be mixed as a brushing glaze or a first-coat dipping glaze.
G2934 with yellow stain (left) vs. a glossy glaze (G2931K with the same yellow stain but fired at cone 03). The matte surface is much easier on the eyes for bright colors (and much more pleasant to the touch).
Right pail: 2 gallons of G2934 base with 10% Cerdec yellow stain. Cost: $135. Jars with the same amount: Almost $300! And you have to paint them on in three coats with drying in between. The one in the pail is a true dipping glaze. You can dip a bisque mug for 2 seconds and it dries immediately in a perfectly even layer (if mixed according to our instructions).
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|Plainsman Clays Ltd.|
702 Wood Street, Medicine Hat, Alberta T1A 1E9
Phone: 403-527-8535 FAX:403-527-7508