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Alberta Slip

Albany slip substitute

Alternate Names: Archie Bray Slip

Oxide Weight323.81
Formula Weight356.62
If this formula is not unified correctly please contact us.

This material was formulated as a physical and chemical substitute for the late and very popular Albany Slip from New York state. Like Albany it is a low melting iron stained clay. Alberta Slip is more consistent than Albany was since it is made from a blend of raw materials.

Alberta slip has a slightly lower iron content than Albany had so some glazes may not fire as dark (this can be counteracted by adding additional iron oxide). Alberta slip melts as well and works in most glazes that call for Albany. Alberta slip is more plastic (less silty) so recipes containing larger proportions may shrink and crack during drying.

Complete information on how it was formulated can be found in the book Magic of Fire available from Digitalfire Corp. and at the web site http://digitalfire.com.

Plainsman Clays has made this material for many years and it is established in the market place across North America. You can use it at 100% to create a chocolate brown glossy glaze at cone 10 (but there is a problem with doing this as we shall see in a moment). Many Albany glazes are based on the addition of an active flux that increases melt fluidity so much that greenish and yellowish crystals grow on cooling to completely change the character of the surface. Many black glazes are also based on Alberta Slip, since it already contains lots of iron you only need to add a little more and some extra cobalt or manganese.

The plasticity of Alberta Slip is helpful where smaller amounts are used since it can assume the burden of suspending the glaze.

The analysis of this material was changed here in Sept 2013, not because the material changed, but because they switched to an actual assay instead of a calculated analysis.

Two runs of Alberta slip plus 20% frit 3134 in a flow test comparison at cone 6.

Alberta Slip in the common 11% lithium and 4% tin Albany slip cone 6 glaze.

The rutile mechanism in glazes

2,3,4,5% rutile added to a 80:20 mix of Alberta Slip:Frit 3134 at cone 6. This variegating mechanism of rutile is well-known among potters. Rutile can be added to many glazes to variegate existing color and opacification.

95% Alberta Slip plus 4% iron at cone 10R

Cone 10R beanpot glazed with Alberta Slip (100%).

Something is definitely wrong. What is it?

An example of how a glaze that contains too much plastic has been applied too thick. It shrinks and cracks during drying and is guaranteed to crawl. This is raw Alberta Slip. To solve this problem you need to tune a mix of raw and calcine material. Enough raw is needed to suspend the slurry and dry it to a hard surface, but enough calcine is needed to keep the shrinkage low enough that this cracking does not happen. The Alberta Slip website has a page about how to do the calcining.

GA6-A Alberta Slip base on the insides of two bowls

This has produced a defect free fired surface at cone 6 oxidation on a dark and light burning clay body. To get this type of surface for stoneware bodies it is important to soak the kiln at cone 6, then cool it 100 degrees F and soak it again for half an hour. For coarser clays it is also helpful to program a 200 degree per hour cool all the way down to 1500F.

Alberta and Ravenscrag Slip pure at cone 5 reduction

At cone 5R pure Alberta Slip (left) is beginning to melt and flow down the runway of this tester. It is producing a matte gunmetal surface. Pure Ravenscrag Slip (right) is just starting (it needs frit to develop melt fluidity at this temperature). The iron in the Alberta Slip is melting it because of the reduction atmosphere in the kiln (it does not move like this in oxidation).

Alberta slip GA6A glaze (with 20% frit 3134) firing at cone 5R (left) compared to a slow cooled iron crystal glaze firing in oxidation (right).

Metallic deep purple by firing pure alberta slip at cone 10R, then refiring at cone 6 oxidation.

Alberta slip and Ulexite at cone 6

90% Alberta Slip (which is a mix of half and half raw and calcine) and 10% Ulexite fired at cone 6. A dazzling fluid dark amber transparent. You could also do this using frit.

Alberta Slip as-a-glaze at cone 10R

This is 100% Alberta Slip (outside) on a white stoneware clay fired to cone 10R. The glaze is made using a blend of 60% calcine and 40% raw (as instructed at the albertaslip.com support website). Alberta Slip was originally formulated during the 1980s (using Insight software) as a chemical duplicate of Albany Slip. The inside: A Ravenscrag Slip based silky matte.

Will this crawl when fired? For sure!

This dry glaze is shrinking too much, it is going to crawl during firing. This common issue happens because there is too much plastic clay in the glaze recipe (common with slip glazes). Clay is needed to suspend the other particles (they would quickly settle to the bottom of the bucket without it), but too much causes excessive shrinkage. Fixing this problem is not nearly as difficult as most people think. You can reduce shrinkage by calcining part of the clay or swapping a clay component for another of similar chemistry but lower shrinkage. The best way: Use glaze chemistry to source some Al2O3 (contributed by the clay) from feldspar instead. Of course this involves juggling amounts of other materials in the recipe to maintain the overall chemistry.

Plainsman H450 (left) vs. H550 celadon glazed mugs

The inside glaze is pure Ravenscrag Slip and the outside glaze is a 50:50 mix of Ravenscrag and Alberta Slips. Each of the glazes employs an appropriate mix of calcined and raw clay to achieve a balance of good slurry properties, hardening and minimal drying shrinkage. Ravenscrag needs less calcined since it is less plastic than Alberta Slip.

Out Bound Links

In Bound Links

By Tony Hansen

XML for Import into INSIGHT

<?xml version="1.0" encoding="UTF-8"?> <material name="Alberta Slip" descrip="Albany slip substitute" searchkey="Archie Bray Slip" loi="0.00" casnumber="70694-09-6"> <oxides> <oxide symbol="CaO" name="Calcium Oxide, Calcia" status="" percent="5.900" tolerance=""/> <oxide symbol="MgO" name="Magnesium Oxide, Magnesia" status="" percent="3.900" tolerance=""/> <oxide symbol="K2O" name="Potassium Oxide" status="" percent="3.500" tolerance=""/> <oxide symbol="Na2O" name="Sodium Oxide, Soda" status="" percent="2.200" tolerance=""/> <oxide symbol="P2O5" name="Phosphorus Pentoxide" status="" percent="0.100" tolerance=""/> <oxide symbol="TiO2" name="Titanium Dioxide, Titania" status="" percent="0.300" tolerance=""/> <oxide symbol="Al2O3" name="Aluminum Oxide, Alumina" status="" percent="15.200" tolerance=""/> <oxide symbol="SiO2" name="Silicon Dioxide, Silica" status="" percent="53.540" tolerance=""/> <oxide symbol="Fe2O3" name="Iron Oxide, Ferric Oxide" status="" percent="4.500" tolerance=""/> </oxides> <volatiles> <volatile symbol="LOI" name="Loss on Ignition" percent="9.200" tolerance=""/> </volatiles> </material>

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