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, 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. This means that there may be some isolated specks. Still, it is far whiter and cleaner than any other product we make.
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"). Do not attempt to use Polar Ice if it is too soft, stiffen it before use to experience the full plasticity and best drying.
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, so older runs might be too stiff. 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.
It is like a rock in the box, but softens dramatically when you cut a piece and start to move it. We must pug softer to be able to process it.
Wedging: Thorough wedging is a must (to loosen it up, remove laminations, create homogeneity). If you are unable to wedge effectively it may be 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 if you stiffen the body to optimal throwing stiffness, it will be 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 and have gone to cone 8 oxidation (with more warping) and cone 10 reduction (with surprising good results without 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.
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.
Commercial brush-on glazes offer many colors and surfaces. For functional ware check for glaze fit (vital for quality functional ware). Do not assume food safety of brightly colored glazes in your kiln and with layering without a leach test (e.g. GLLE test). Consider using transparent or white liner glazes for food surfaces.
Mixing your own glazes is practical (with our clear guidelines even beginners can make dipping glazes that go on silky smooth and evenly and dry in seconds). If you already do this using recipes from the web, be careful. High-feldspar glazes (having more than about 35%) often craze. Ones that rely on high melt fluidity to encourage crystallization and variegation (often because of excessive Gerstley Borate, lithium carbonate, zinc or Frit), view these with suspicion for leaching and cutlery marking; test them well (also test the additionless versions). Be suspicious of any glaze not having good documentation.
The best approach is to begin with a good transparent base you understand and that fits. We supply (as products and recipes) G2926B glossy whiteware and G2934 matte frit-fluxed bases. Their documentation describes how to mix, use, fire and adjust them and showcases stain, color and variegator additions to create an infinite number of effects. The former, G2926B, may not have a enough melt fluidity to create non-food-surface reactive visual effects with certain colors and variegators. G3806C fluid-melt recipe is an alternative (but check for crazing). These pages also reference other base glazes that might be of interest.
Crazing: Functional ware must remain craze-free (crazing is unsanitary and drastically reduces ware strength). Because ware is not crazed out of the kiln does not mean it will not do so with time. Do cycles of a boiling water:ice water immersions (BWIW test) on a piece to test glaze fit (by stressing it to bring out any crazing or shivering tendencies).
Glaze slurry consistency and quality: In freshly mixed or stored glazes that do not have natural thixotropy a secret to achieving even coverage is inducing it by additions of a flocculant. A glaze of the right specific gravity and having a slightly gelled condition goes on to bisque ware evenly, does not drip and dries in seconds. Always screen glazes when first making them (80 mesh). Be alert to any particulate that may appear after storage (e.g. precipitates) and screen again if needed.
For slip decoration and engobes be careful to match the fired shrinkage of the slip with the body. Where we do not recommend a specific engobe recipe use a formula based on the porcelain itself. Add 2% VeeGum or Bentonite (the extra stickiness helps it adhere well to leather hard ware). Be careful about adding fluxes (e.g. frit), this increases fired shrinkage (the mismatch with body can cause flaking) and can compromise opacity.
If you want to develop and mix your own glazes and engobes consider getting an account at http://insight-live.com. You can organize a methodical development program and adopt better methods of testing (e.g. melt fluidity, thermal stress, slip-fit tests).
Like the plastic version of Polar Ice, do not compare this with other casting bodies you may have used. This requires much more care and better mixing to deflocculate and get the slurry to the right consistency (however it may very well cast faster and thinner that others). Polar Ice Casting will also warp on firing if pieces are thin (of course you are likely using it for that very purpose so it is up to you to make stable shapes that are small enough to fire successfully). It is important to understand the principles of deflocculation, be able to measure specific gravity efficiently and have a good propeller mixer to make good casting slip.
This contains 1% VeeGum to impart the plastic strength that enables pieces to pull away from the mold (this requires double the normal amount of Darvan). While this might not seem desirable, you will find its ability to cast very thin pieces (as little as 1 mm) is outstanding. However before deciding on a casting process in favour of throwing remember that standard Polar Ice of the right stiffness can be thrown very thin.
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!
Polar Ice Casting (not quite the same recipe as plastic Polar Ice, it has less VeeGum) has very good casting properties (but only if properly deflocculated). You even use heat-lamps or fans to get mold extraction within minutes of pouring. For very thin pieces, use a very sharp knife when cutting away excess around the rim (to prevent splitting). Assuming the 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
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 will not be a problem (unless there is too much in which case it may settle out). 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.
We do not supply a thermal expansion value. The reason is that such numbers often mislead users. First, a body has different thermal expansion characteristics when fired at different temperatures, schedules and atmospheres. Dilatometers are only useful when manufacturers can measure bodies and glazes over time and in the same firing conditions. If a chart is supplied here, please view only as a way to compare one body with another.
Another significant issue is that many customers compare measured thermal expansion numbers with calculated values of glazes in efforts to fits those glazes to a body. This does not work. Calculated values are relative only and have limitations that must be understood. The best way to fit glazes to your clay bodies is by testing, evaluation, adjustment and retesting. For example, if a glaze crazes, adjust its recipe to bring the expansion down (using your account at insight-live), fire a glazed piece and thermal stress it (using an IWCT test, 300F into ice-water). If it still crazes, repeat the process.
If we recommend a base clear or glossy glaze, try calculating the expansion of that as a rough guide to know whether your glazes will fit.
Drying Shrinkage: 5.5-6.5% Dry Strength: n/a Water Content: 21.0-22.0 Drying Factor: C130
Sieve Analysis (Tyler mesh):
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%
Compared to Others
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.
Safety Data SheetClick here for web view.
|Plainsman Clays Ltd.|
702 Wood Street, Medicine Hat, Alberta T1A 1E9
Phone: 403-527-8535 FAX:403-527-7508