The secret to cool bodies and glazes is alot of testing. But how will you be able to learn from that testing without a good place to store the recipes? Document the successes and failures? Do it in your account at https://insight-live.com.

Alberta Slip Lithium Brown Cone 6 Low Expansion

Code: GA6-G1
Modification Date: 2015-10-30 18:55:42
Member of Group: AS6

Plainsman Cone 6 Alberta Slip based glaze. It can be found among others at http://albertaslip.com.

MaterialAmount
Alberta Slip40.039.7%
Alberta Slip Calcined35.034.7%
Ferro Frit 324917.016.9%
Silica4.04.0%
Lithium Carbonate4.84.8%
 100.80  

Firing Schedule

Rate (F)Temp (F)Hold (Min)Step
100220601
300173302
1082175153
1502075304

Notes

The regular Alberta Slip lithium brown recipe crazes on porcelain. This one was formulated to maintain the appearance but reduce the thermal expansion. It does this by reducing the KNaO and increasing the MgO. This was effected by employing MgO sourcing frit 3249. This frit is more expensive and difficult to get but it is the only way we have found to effectively reduce the thermal expansion and maintain the aesthetic.

Like the original albany glaze, this recipe contains lithium carbonate (which is partially soluble), thus the slurry can gel over time. This necessitates the addition of water and increases the drying shrinkage and there cracking (which results in crawling). We are working on substituting a lithium frit to eliminate this issue.

Some glazes look great on red clay and horrible on white

Some glazes look great on red clay and horrible on white

Alberta Slip cone 6 lithium brown (GA6-G1) on a red burning clay (left Plainsman M390) and buff burning (right M340). Obviously this looks better on the former where iron from the underlying body variegates the entire surface and bleeds through on contours where the glaze is thinner, creating a breaking effect.

Fine tuning glaze shrinkage vs. hardness

Fine tuning glaze shrinkage vs. hardness

These mugs are fired at cone 6 with GA6-G1 Alberta Slip lithium brown. The difference: the ratio of raw to calcine Alberta Slip. In this glaze, a 50:50 ratio was not working well (left). The glaze was shrinking too much on drying, then crawling on firing (it needs to be thickly applied to get the visual effect I want). I mixed the recipe using pure calcine Alberta Slip, then repeated a cycle of pouring a little of this into the 50:50 mix and trying it. I kept doing that and glazing another mug until I had a minimum of drying cracks (while still having good gelling, application properties and dry hardness). The mug on the right was the last cycle, it has fired perfect. Using this technique I can perfect the ratio of raw:calcine for each Alberta Slip glaze I use.

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.

Out Bound Links


By Tony Hansen

+


Feedback, Suggestions

Your email address

Subject

Your Name

Message


Copyright 2003, 2008, 2015 https://digitalfire.com, All Rights Reserved