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Alberta Slip Tenmoku Cone 10R

Code: GA10-B
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

MaterialAmountPercent
Alberta Slip Calcined50.046.7%
Alberta Slip50.046.7%
Additions
Calcium Carbonate5.04.7%
Iron Oxide2.01.9%
 107.00  

Firing Schedule

Rate (C)Temp (C)Hold (Min)Step
1012001
5055002
10098003
50130004
01300305
Freefall306

Notes

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.

Tenmokus made from Alberta Slip and Ravenscrag Slip

Tenmokus made from Alberta Slip and Ravenscrag Slip

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.

Which tenmoku base is better: Alberta Slip or a clear glaze?

Which tenmoku base is better: Alberta Slip or a clear glaze?

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.

Ravenscrag Tenmoku vs. Alberta Slip Tenmoku on porcelain

Ravenscrag Tenmoku vs. Alberta Slip Tenmoku on porcelain

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).

Ravenscrag Tenmoku vs. Alberta Slip Tenmoku

Ravenscrag Tenmoku vs. Alberta Slip Tenmoku

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).

Calcining Alberta Slip

Calcining Alberta Slip

Calcined Alberta Slip (right) and raw powder (left). These are just 5 inch cast bowls, I fire them to cone 020 and hold it for 30 minutes. Why calcine? Because for glazes having 50% or more Alberta Slip, cracking on drying can occur, especially if it is applied thick (Alberta Slip is a clay, it shrinks). I mix 50:50 raw:calcine for use in recipes. However, Alberta Slip has an LOI of 9%, so I need to use 9% less of the calcine powder (just multiply the amount by 0.91). Suppose, I needed 1000 grams: I would use 500 raw and 500*.91=455.

Alberta slip vs Alberta Slip tenmoku

Alberta slip vs Alberta Slip tenmoku

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).

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By Tony Hansen

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