The whitest, most translucent yet most plastic porcelain we make. A casting version is also available.
Plainsman Polar Ice, P300, M370 and M340 with G2926B Whiteware transparent glaze on the porcelain (G2916F Stoneware transparent on the M340).
This body employs New Zealand Halloysite, a super-white-burning kaolin. To that it adds the highest quality ceramic plasticizer available. The full throwing version is a no-compromise product. It is the most translucent, the strongest, the whitest and the most plastic clay body you likely have ever used!
Disclaimer: The price of Polar Ice is a reflection of how expensive it's materials are and how difficult it is to pug. Notwithstanding that, we do not have filter-pressing, slurry-screening, pre-pugging and stainless-steel pugging equipment (if we did the price would be far higher). Even if we did have such equipment this body would be too sticky to filter-press or pre-pug. There may be grease spots (from the pugmill bearings) and slug surface coloration (from bacteria growth or the oil used to keep it from sticking to the conveyor). There may also be isolated fired specks or hard chunks. This is not a body for one-of-a-kind or heavy pieces, but it is well suited to a commitment where one develops a production method for thin-walled pieces and makes enough product to afford to lose a few. With more experience success rates will improve and you will make ware impossible with any other body.
Using Polar Ice is more of a commitment than other bodies. Compromises are required, expectations are different.
Plasticity: Polar Ice is extremely plastic. Others claim to be plastic, but they use the word in a relative sense (meaning "a little less short than other really flabby porcelains"). However it is only plastic when not too soft (do not attempt to use Polar Ice if it is too soft).
Stiffness: To properly pug it we must run it too soft (you will notice this if you buy a newer run). However, it will stiffen over time. Consider keeping a box of stiffer material around so you can wedge it together will softer to get the right consistency. Failing that, reduce water content on a very clean plaster surface or leave a lump under a cloth over night or longer. It is imperative to wedge different stiffnesses together well or throwing will be adversely affected.
Polar Ice is not ready-to-use out-of-the-box. It comes out like a rock and then softens to a sticky, unusable mass when wedged! Flatten pieces on clean plaster bats to dewater for a while, then wedge thoroughly (repeat until it is no longer sticky). When it is wedged really well and the stiffness is right it will want to go taller and thinner than any clay you have ever thrown!
Wedging: Thorough wedging is a must (to loosen it up, remove laminations, create homogeneity). If you are unable to wedge effectively it is better to use a different body.
Stickiness: This is the most prominent side effect of the plasticity. It will stick to your hands, to the table, to the cutting wire, anything that touches it. During trimming it will stick back to itself and tools. If you attach ware to the wheelhead with water to trim, it will stick fast. After trimming it balls up under your fingers if you attempt to round corners by pressing on them. However when stiffened to optimal throwing stiffness, it is much less sticky.The stickiness is an asset when joining, the slip glues it well (if adequate pressure is applied).
Drying: Thin ware of even thickness, few joins and dried under conditions where degree-of-wetness is always kept the same throughout, these will dry the best. Thick ware of uneven thickness, lots of joins and dried unevenly will crack the most. Drying pieces under plastic, without a cloth over them, will often produce issues.
The stickiness and plasticity of this body make it a favourite for this application. Layers adhere well and pieces hold up even though the clay is soft.
We have had consistent results firing to cone 6 oxidation. We formulated it so that a thin-walled, vertical-sided mug with flared lip will not pull to an oval-shaped rim during firing (by the weight of the handle). Notwithstanding this, in our lab we can get translucency down to cone 4. We have fired it to cone 8 oxidation (with more warping) and cone 10 reduction (with surprisingly good results and little warping). Very durable and strong ware can be made using this body.
To get maximum translucency it is not necessary to fire over cone 6. The casting version is not quite as translucent as the throwing version. However the walls of cast piece are generally much thinner to compensate for this. You can enhance the translucency of the casting version by additions of Ferro Frit 3110 (e.g. 5%).
As with any body, bisque fire it to the highest practical temperature (high enough to burn out undesirables, but low enough to have the needed porosity for glazing). Cone 06 is a good starting point.
Impeccable cleanliness is needed to minimize fired specking for transparent glazes. At the same time, we cannot guarantee a completely speck-free result. This body is not filter pressed. While this background mug is speck free, the other two are not. The blue speck on the mug rim (right) is likely contaminant picked up during the process. The small black ones on the left could have come in the material.
Polar Ice fired bars (cone 4-8 oxidation bottom to top). At cone 8 the body is very glassy and beginning to melt.
Polar Ice casting requires extra care, good mixing and some compromise to get a slurry of the right consistency (it is important to understand the principles of deflocculation, be able to measure specific gravity efficiently and have a good propeller mixer). This contains a plastizer to impart the plastic strength to better enable pieces to shrink and pull away from the mold (this requires double the normal amount of Darvan and lengthens casting time considerably, M370 is easier to cast and mix). Polar Ice pieces will warp on firing if they are thin or shapes are unstable.
Because of the magic of defloccualtion you can mix all this powder into that little bit of water! This 20 Kg bag of porcelain needs only 9 Kg of water in the bottom of that pail. The secret is that the water contains a small amount of Darvan, it makes the particles repel each other electrolytically enabling a fluid slurry with only a little more water than is in a throwing clay!
Casting properties depend on proper deflocculation. Assuming viscosity and specific gravity are good, and you have good molds, the slip will drain well and wall thicknesses will be even. Watch out for powdery or dry-feeling pour surfaces (shortly after pouring out the slip), these mean over deflocculation.
Recipe Used in the Plainsman Lab
67.3% Polar Ice Casting Mix Powder
32% Water (distilled recommended)
0.7% Darvan No. 7
This is a 100-total recipe, that means 67.3 parts-by-weight of powder and 32 parts-by-weight of water.
This should produce a specific gravity of around 1.7 with a Ford Cup viscosity of 40 seconds (Laguna Viscometer reading of 140 seconds). Polar Ice cannot tolerate over-deflocculation well, that is why we are using a conservative recipe with a lower-than-typical specific gravity (contact us if you have issues). If your slip is not flowing well enough consider adding more water rather than more Darvan.
Water and Darvan percentages are not cast-in-stone, adjust as needed. Add 90% of the Darvan to the water and mix it in. Then add the powdered body mix to the water under a propeller mixer. It might appear that it is impossible to get that much powder into the available water, but that is the magic of the Darvan. Mix at least 15 minutes. If you cannot get the last of the powder in, add the rest of the Darvan. Do a preliminary assessment:
If you are not doing alot of production and can tolerate your molds getting wetter (and longer mold extraction times), adding water to the slurry will not be a problem (although too much may cause settling issues). Remember also that warm slip will flow better than cold.
You can find information on the mixer we use in our lab at http://digitalfire.com/4sight/education/a_one-speed_lab_or_studio_slurry_mixer_361.html.
You can make about 1 US gallon from 5000 grams of powder. You can make about 1 Canadian gallon from 6300 grams.
Drying Shrinkage: 5.5-6.5% Dry Strength: n/a Water Content: 21.0-22.0 Drying Factor: C130
100-150: 0.1-0.3 150-200: 0.5-1.0
Cone 5: 8.0-9.0 Cone 6: 8.5-9.5 Cone 7: 8.5-9.5
Cone 5: 0% Cone 6: 0% Cone 7: 0%
Competing NZ Porcelains from Other Manufacturers: Polar Ice is likely very different. We are pretty sure you have never used anything like this before!
21 mugs made from 1/2 box of clay, 10 kg ( (all scrap was reclaimed). Polar Ice is plastic and you can make more pieces because it can be thrown thinner than most other clays. These have a weight-to-capacity ratio of 1.09 (each 1 gram of fired porcelain can contain 1.09 grams of water). This is the highest of any of our products.
|Plainsman Clays Ltd.|
702 Wood Street, Medicine Hat, Alberta T1A 1E9
Phone: 403-527-8535 FAX:403-527-7508