Modification Date: 2016-10-15 20:42:41
Member of Group: AS10
You can make a tenmoku from Alberta Slip by adding only 2% iron oxide and 5% calcium carbonate
|Alberta Slip 1000F Roasted||50.0||46.7%|
|Rate (C)||Temp (C)||Hold (Min)||Step|
Tenmoku glazes normally contain 10%+ iron oxide, they are extremely messy to use and often have poor slurry suspension properties and are difficult to apply evenly. This recipe is totally different, it is so much cleaner to use. It applies very evenly and suspends well.
Uou can adjust the drying hardness, drying shrinkage and suspension properties by adjusting the proportion of calcined to raw Alberta Slip (see the preparation page at http://albertaslip.com for more information). You can change the degree of melting by adjusting the calcium carbonate and the intensity of color by tuning the iron oxide.
GR10-K1 Cone 10R Ravenscrag Tenmoku (right) compared to Tenmoku made from Alberta Slip (left, it is 91% Alberta Slip with 5% added calcium carbonate and 2% iron oxide). Left is Plainsman P700 porcelain, right is H570. Tenmokus are popular for the way they break to a crystalline light brown on the edges of contours.
Right: Alberta slip is almost a Tenmoku glaze by itself at cone 10 reduction. To go all the way only 1-2% more iron is needed (plus a little extra flux for melt fluidity, perhaps 5% calcium carbonate). Compare that to crow-baring a clear glaze into a tenmoku (left): This is G1947U plus 11% red iron oxide. That produces a slurry that is miserable to work with (it stains everything it comes into contact with) and turns into a jelly on standing.
Body is Plainsman P580. Far left: G2894 Ravenscrag Tenmoku with 10% whiting and 10% iron oxide added. Center: Pure Alberta Slip plus 5% whiting and 1% iron oxide. Right: Pure Alberta Slip plus 5% whiting and and 2% iron. The Alberta Slip versions are less messy to use because so much less iron is needed (iron also causes the slurry to gel). The Ravenscrag and higher iron Alberta Slip versions are running, they are too fluid. The rust colored crystals are not developing the way they did with these glazes on an iron stoneware (in the same firing).
All of these are on a cone 10 reduction fired iron stoneware (Plainsman H443). Far left: G2894 Ravenscrag Tenmoku with 10% whiting and 10% iron oxide added. Center: Pure Alberta Slip plus 5% whiting and 1% iron oxide. Right: Pure Alberta Slip plus 5% whiting and and 2% iron. The Alberta Slip versions are less messy to use because so much less iron is needed (iron also causes the slurry to gel). The Ravenscrag version is running, it is too fluid. Likely 5% calcium carbonate would be enough (and maybe less iron).
Roasted Alberta Slip (right) and raw powder (left). These are thin=walled 5 inch cast bowls, fired to 1000F and held it for 30 minutes. Why calcine? Why 1000F? Because Alberta Slip is a clay, it shrinks on drying. Roasting eliminates that, a 50:50 raw:roast mix works well for most recipes having high percentages. And 1000F? Calcining to 1900F sinters particles together (creating a gritty material) while 1000F just does not. But note the difference: The raw powder has an LOI of 9% (looses 9% weight on firing). 1900F-calcine has zero%. 1000F-roast has only 3%. So we need 6% less (9%-3%) of it than of the raw to supply the same chemistry. For example, if a recipe calls for 1000 grams of Alberta Slip: Use 500g raw and 456g 1000F roast (500*.94).
Alberta Slip 100% (left) and Alberta Slip Tenmoku (right). The tenmoku is a little more opaque and forms the characteristic brown crystals on edges of contours (e.g. rim).
Out Bound Links
You can make a black glaze at cone 10R using only 1% black stain in a 100% calcine:raw mix of Alberta Slip
2003-12-12 - Alberta Slip is a great base for black glazes at cone 10 reduction, only 1% black stain is needed to obtain a jet black glossy. Increasing amounts of ...
By adding a little iron to 100% Alberta Slip you can make an iron crystal glaze.
2003-12-18 - Typically this type of glaze is made by adding up to 15% iron oxide to a transparent glaze. However using Alberta Slip, you only need 3% iron (this is...
A reduction fired glaze having about 10-12% iron oxide that fires to a highly glossy deep maroon to black. Tenmokus normally break to iron-red crystallized areas where thinner and thus work well to visually highlight incised decoration or abrupt contours. Tiny yellow iron silicate crystals adorn thi...
In Bound Links
Plainsman Cone 10R Ravenscrag Slip based glaze. It can be found among others at http://ravenscrag.com.
2012-08-27 - Like a typical tenmoku, this fires to a brilliant deep gloss that will run if applied too thickly. It appears best on porcelain on white stoneware. Ti...
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By Tony Hansen