Greenbarn Potter's Supply Ltd.

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Open Mo-Fr 8:30-5PM, closed Sat, Sun and long weekends.

Next closure for stat holiday is for Canada Day, closed on July 1, and re-open on July 2.

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Plainsman Products


Clays

  Low Temperature Clays
  Medium Temperature Clays
  High Temperature Clays
  Porcelains
  Other Clays
  Native Clays
  Casting Slips

Materials

  Dry Materials
  Stains
  Encapsulated Stains
  Liquids

Glazes

  Spectrum Opaque Gloss Low Fire Glazes
  Spectrum Semi-Transparent Low Fire Glazes
  Spectrum Satin Matte Low Fire Glazes
  Spectrum Crackle Glazes
  Spectrum Metallic Glazes
  Spectrum Raku Glazes
  Plainsman Dry Glazes
  Potter's Choice Cone 5/6 Glazes
  Celadon Cone 5/6 Glazes
  Moroccan Sand Glazes
  Spectrum Hi Fire Cone 6 Glazes
  Spectrum Shino Glazes Cone 6
  Spectrum Celadon Glazes Cone 6
  Liquid Brights

Underglazes

  Spectrum 500 Underglazes
  Underglaze Tools
  Amaco Velvet Underglazes

Enamelling

  Enamelling Supplies
  Enamelling Tools

Equipment

 Kilns
  Electric Pottery Kilns
  Electric Glass Kilns
  Kiln Furniture
  Cones
  Elements
  Kiln Parts, Accessories
  Exhaust Systems
  Refractories
  Potter's Wheels
  Slab Rollers
  Hand Extruders
  Pugmills
  Scales
  Banding Wheels
  Air Brushes

Tools

  Brushes
  Throwing Tools
  Trimming, Turning, Cutting Tools
  Wood/Bamboo Tools
  Wire and Wood Tools
  Rollers/Stamps
  Decorating Tools
  Glazing Tools
  Ribs & Scrapers
  Ribbon/Wire Tools
  Rasps
  Knives, Needle Tools, Cutters
  Sculpture Tools
  Tool Kits
  Unclassified

Accessories

  Miscellaneous Accesories
  Corks/Stoppers
  Cork Pads
  Oil Lamp Accessories
  Dispenser Pumps
  Teapot Handles
  Bisque Tiles

Western Canada's largest distributor of pottery materials and supplies. Clays, raw materials, tools, wheels, kilns, slabrollers, books & much more.

Our continuing goal is to supply artists, potters and crafts people with great quality products, knowledge and customer service. Our staff is familiar with all the items we stock and can help you through the selection and ordering process. We will also see that your order is shipped according to your directions, or put together for pick up at our retail store in Surrey, BC.

Kilns for Sale at 60% off - oddballs need good homes!

The following two kilns are in stock, brand new in the box, and are now discounted until each are sold!

1. Skutt Scarab, Flameworking Glass Kiln, 27x16x12" inside, 240volt/1phase. $8335 reg.

- now on sale at 60% less. $3334 + tax

2. Skutt Scarab Mini, Flameworking Glass Kiln, 12x16x12" inside, 240volt/1phase. $6055 reg.

- now on sale at 60% less. $2422 + tax

Sculpture Materials on Sale!

The following items are now discounted while stock remains!

1. Roma Plastilina, Grey/Green, oil based clay, offered in soft/med/firm

- now at 25% discount. Sale priced at $19.19/2Lb block + tax

2. Armature Wire (not intended for firing within a kiln):

- 1/16" by 32' roll: now at 25% discount. Sale priced at $6.19/roll + tax

- 3/16" by 10' roll: now at 25% discount. Sale priced at $11.49/roll + tax

- 3/8" by 10' roll: now at 25% discount. Sale priced at $17.89/roll + tax

Technical Tips Blog

CMC Gum does not work well in a glaze if an important ingredient is missing

Bentonite and CMC working together

On the left, the brush-strokes of gummed glaze, which I batched myself, have been freshly painted onto an already-fired glaze. Notice the brown brush stroke holds its character. It has a high specific gravity (SG): 1.6. And contains 1.5% CMC gum. The white one to its left, whose brush stroke has flattened and it is running downward, has the same gum content but an SG of 1.5. Is it running because of its lower SG? No. Commercial glazes with an SG below 1.3 still hold in place well. How? Because they also have a gelling agent (e.g. Veegum - it has an unfortunate name, it is not a gum). That reveals a secret: Gums and gelling agents need each other. CMC Gum needs particle surface area to work its magic and bentonite, the gelling agent here, supplies that. And, the gelling agent needs the gum to slow down drying and enable a hard and crack-free dried surface. The dried strokes on the right demonstrate that - 2% bentonite has been added to the drippy one on the far left. They held in place because of the bentonite and hardened without cracking because of the CMC gum.

Context: CMC Gum, Bentonite, Veegum, Brushing Glaze

Monday 15th July 2024

Low fire mug survives two-foot drop on to cement

In slow motion. This is Plainsman Snow clay, a super white burning dolomite body. Fired at cone 04. Although low-temperature ware is not as strong as stoneware it has more elasticity. Other than a tiny chip out of the base and handle, this mug still has the ring of strength. Where does this piece get all this strength? 1. It is glazed inside and out. 2. Glazes adhere well to this porous body, forming a deep interface. 3. The compression under which the glazes exist not only resists crazing but adds a lot of strength to the piece. Notice how it bounces onto the handle also!

Context: Fired Strength

Friday 5th July 2024

Cone 10 Reduction with Alberta and Ravenscrag Slips

Outside is the GR6-A recipe (made using 50:50 roasted and raw Alberta Slip), there are no other additions. The inside is pure Ravenscrag Slip GR10-A (also a 50:50 mix of roast:raw), with no additions. The clay is Plainsman H550. The firing schedule is C10RPL.

Friday 5th July 2024

Variegating effect of sprayed-on layer of titanium dioxide

Pure titanium as a varieagant

The base glaze (inside and out) is GA6-D Alberta Slip glaze fired at cone 6 on a buff stoneware. However, on the outside the dried-on glaze was over-sprayed with a very thin layer of titanium and water (VeeGum can be used to help gel the sprayable titanium slurry and suspend it). The dramatic effect is a real testament to the variegating power of TiO2. An advantage of this technique is the source: Titanium dioxide. It is a more consistent source of TiO2 than the often-troublesome rutile. Another advantage is that the variegation can be selectively applied in specific areas or as a design. This effect should work on most glossy glazes having adequate melt fluidity.

Context: Titanium Dioxide, GA6-D, Reactive Glazes, Crystallization, Glaze Layering, Variegation

Thursday 4th July 2024

A mug cracks before your eyes because of glaze compression

The glaze on this highly vitreous, thin-walled mug is normally perfect, it is under enough thermal compression to really increase ware strength. But, since this mug is glazed inside only, the compression is too great. While it looks OK, the glaze is constantly pressing outward, looking for relief. Watch as a tap with a spoon is enough to trigger a sudden crack. And it opens under the pressure, clearly revealing the piece was spring loaded. This is a simple test. A typical mug of this clay would survive hundreds impacts of this nature. Further, this did not happen just because it was not glazed on the outside. A mug with glaze under compression on the inside and under tension on the outside would fail this test even more dramatically.

Context: Is inside-only glazing a.., Glaze Compression

Monday 1st July 2024

The same glaze fires very differently depending on kiln cooling rate

Both mugs use the same cone 6 oxidation high-iron (9%), high-boron, fluid melt glaze. Iron silicate crystals have completely invaded the surface of the one on the left, turning the gloss surface into a yellowy matte. Why? Multiple factors. This glaze does not contain enough iron to guarantee crystallization on cooling. When cooled quickly it fires the ultragloss near-black on the right. As cooling is slowed at some point the iron will begin to precipitate as small scattered golden crystals (sometimes called Teadust or Sparkles). As cooling slows further the number and size of these increases. Their maximum saturation is achieved on the discovery, usually by accident, of the likely narrow temperature range they form at (normally hundreds of degrees below the firing cone). Potters seek this type of glaze but industry avoids it because of difficulties with consistency.

Context: B2O3, Fe2O3, Ravenscrag floating blue color.., The matteness of this.., Alberta Slip GA6-A glaze.., Cooling rate drastically affects.., Same glaze fires hyper-matte.., The appearance of this.., Melt Fluidity, Glaze Chemistry, Crystallization

Monday 1st July 2024

Is inside-only glazing a good idea? We say it is not.

Glaze compression fractures porcelain mug

This mug is made from 325 mesh MNP, the strongest porcelain I have. Since the walls are of even thickness with no abrupt corners or contour changes and the glaze is thinly and evenly applied I thought I could follow a social-media-driven trend and glaze only on the inside. But I got glaze compression time-bombs waiting for hot coffee triggering! Three other mugs failed this same way! But four with this same glaze inside and out were fine. Why? The outside glaze counters the inside one pushing outward. And it closes crack initiation points.

I got lots of pushback on social media saying glaze compression problems are overblown. But I also got stories and pictures much worse than this (especially with thick and drippy glazes). But, some still feel that outside-only glazing can work by carefully tuning the thermal expansion fit between body and glaze. Or even by accident. Either way, there is still an elephant in the room: Glaze fit has to be just right - too much and pieces break, too little and the glaze crazes. That is a problem because it brings intolerance of even slight changes in body, glaze or firing.

Of course, if you make thick-walled ware and the glaze thickness is not really crazy, then you can probably get away with doing everything that I have advised against above.

Context: Drip glazing and bare.., Example of COE curves.., A mug cracks before.., The handle is strong.., Here is how far.., Glaze Compression

Thursday 27th June 2024

A down side of high feldspar glazes: Crazing!

A runny, amber, crazed glaze

This reduction celadon is crazing. Why? High feldspar. Feldspar supplies the oxides K2O and Na2O, they contribute the brilliant gloss and great color but the price is very high thermal expansion. Scores of recipes being traded online are high-feldspar, some more than 50%! There are ways to tolerate the high expansion of KNaO, but the vast majority are crazing on all but high quartz bodies. Crazing is a plague for potters. Ware strength suffers dramatically, pieces leak, the glaze can harbor bacteria and customers return pieces. The simplest fix is to transplant the color and opacity mechanism into a better transparent, one that fits your ware (in this glaze, for example, the mechanism is simply an iron addition). Fixing the recipe may also be practical. A 2:1 mix of silica:kaolin has the same Si:Al ratio as most glossy glazes, this glaze could possibly tolerate 10% of that. That would reduce running, improve fit and increase durability. Failing that, the next step is to substitute some of the high-expansion KNaO, the flux, for the low-expansion MgO, that requires doing some glaze chemistry.

Context: Feldspar, Na2O, ChatGPT is completely wrong.., Cone 1 mug is.., Celadon Glaze, Calculated Thermal Expansion, Limit Recipe, Glaze Crazing

Wednesday 26th June 2024

Preparing clay test bars to measure plastic, dry and fired physical properties

Preparing bars for the SHAB, LOI and DFAC tests

This is being done for SHAB, LOI and DFAC tests. The clay was wedged thoroughly, rolled to 3/8 thickness (using the metal rods as gauges) and then cut to 4 1/4" by 1" bars. Code numbers and specimen numbers are stamped on each (these are needed to enter data into our account at Insight-live). For example, notice that the bars have specimen numbers from 1 to 6. These will be fired at six different temperatures (for a low-temperature body, for example, we fire cone 06, 04, 03, 02, 01, 1, 2). The data measured from each, including the temperature, will be entered for each bar (specimen). The 12cm dia. disk is being cut from 3/16" thickness. Notice how these clay tears as cut, this is an indication of the low plasticity of this native clay material. And notice the greenish color, that is typical of terra cotta clays.

Context: Shrinkage/Absorption Test, Code Numbering

Saturday 15th June 2024

3D-printed plaster mold natches, retainers and embeds

3D printed mold natches

Top left to right: The natch, the retainer, a fragment of a 0.8mm thick 3D printed mold shell and the shallow and deep receptacles that fit snuggly over it.
Lower left: The deep and shallow receptacles are embedded in a test section of plaster, the natches are ready to insert (head first or feet first). The natches have been glued in on the right.
Not shown: Cylindrical retainers that fit inside the embeds. These enable replication of an embed in a case mold to an embed in a working mold.

In some ways, these are preferable to the commercially available natches. First, the embeds enable flexibility in what will be inserted into either case or working molds (the natches, for example, are glued into the embeds). A key advantage of this, vs using commercial natches, is that working molds release from the case molds with flat matting surfaces - meaning they can be sanded to ultimate flatness for optimal fit (since a little warp can happen in the 3D printed block mold). Another advantage is that parametric drawings make it easy to change the sizes of all needed parts. This project is a testament to the accuracy of 3D printing - it is precise enough, on our Prusa MK4, that 1/10 mm is the difference between perfect fit and too tight or too loose.

Context: A demo for using.., Mold Natches

Thursday 13th June 2024

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Greenbarn Potter's Supply Ltd., 9548 - 192nd Street, SURREY, BC V4N 3R9
Phone: 604-888-3411, FAX: 604-888-4247, Email: sales@greenbarn.com