Make and sell your own jars of glaze at your teaching studio

Your studio or workshop can save a lot of money making and even selling your own glazes to students (at least for common colors and types). The supplies shown here enable printing quality labels on ordinary paper and applying them to jars that cost about $2. What about the glazes themselves? Just do what glaze companies do: Add stains to a base transparent glossy or matte glaze (for example G1916Q for cone 04 or G2926B for cone 6). Each 16oz jar needs 350g powder, 450g water, 5g CMC gum and 5g Veegum (leave out the Veegum and use less water for thicker coats). Stains are expensive (5-20 cents/gm here in 2024), at 7.5% (25g) that is $1-5 per jar. The materials for the G1916Q base cost $10/kg, and for G2926B $4/kg. Thus each jar costs $3.33 and $1.33 respectively. Making recipes of 5000g at a time would enable making 15 jars. A best-case is thus about $5/jar, worst case about $10/jar (compare that with commercials that are about $15-70). Of course, you can save money by looking for deals on materials and stains and recycling jars. Consider other advantages of making your own: You can tune the rheology, you know what is in it, you can adjust recipes to fit your clay bodies (to prevent crazing or shivering).

Are you worried about labelled, testing and SDSs? Take a look at ASTM D-4236 and see if you still need to worry.

Related Pictures

Here is my setup to make brushing glazes and underglazes by-the-jar

To make a low SG version of G2934BL I have already weighed out a 340g batch (it contains 5g each of Veegum and CMC gum to gel the slurry and slow the drying). I use 440g of water initially (adjusting that according to experience in brushing behaviour). After shake-mixing all the powder in the plastic bag I pour it into the water on low speed and finish with 20 seconds on high speed. This produces a low specific gravity brushing glaze, it just fills this 500ml jar. In subsequent batches, I adjust the Veegum for more or less gel and the CMC for slower or faster drying. Later I also assess whether the CMC gum is being degraded by microbial attack - often evident if the slurry thins and loses its gel. Since each glaze recipe responds differently and changes differently over time, good notes are essential. We are working on dozens of these at any given time, each is code-numbered in our group account at Insight-live.com. This is so worthwhile doing that I make quality custom labels for each jar!

Links

URLs	https://www.uline.ca/BL_6409/3M-Label-Protection-Tape 3M Label Protection tape
URLs	https://www.uline.ca/BL_7304/Label-Protection-Tape-Dispensers 3M Label Protection Dispenser
URLs	https://www.uline.ca/Product/Detail/S-14510/Jars/White-Round-Wide-Mouth-Plastic-Jars-16-oz-White-Cap White 16oz 500ml plaster jars
URLs	https://plainsmanclays.com/store/index.php?find=stain&pictureflow=1&iframe=0 An example of ceramic stains sold at a supplier
URLs	https://www.astm.org/d4236-94r21.html ASTM D-4236 - Standard Practice for Labeling Art Materials for Chronic Health Hazards - It is not what you think! A standard that "applies exclusively to art materials packaged in sizes intended for individual users of any age or those participating in a small group". It "concerns those chronic health hazards known to be associated with a product or product component(s) when it is present in a physical form, volume, or concentration that in the opinion of a toxicologist has the potential to produce a chronic adverse health effect". The word "toxicity" is not mentioned on the page nor any methods for determining such. Furthermore, the labelling refers to hazards to which the potter is exposed in applying the glaze to the ware, long term, in small hobby quantities. IT DOES NOT ADDRESS leaching hazards the ware presents to users of the pottery. Even then, the standard states that "it is the RESPONSIBILITY OF THE USER ... to establish appropriate safety, health, and environmental practices ... based upon knowledge that exists in the scientific and medical communities". It also admits that "since knowledge about chronic health hazards is incomplete and warnings cannot cover all uses of any product, it is not possible for precautionary labelling to ensure completely safe use of an art product." It is interesting that one manufacturer displays this warning on pages relating to dipping glazes and accessory products (which are used by manufacturers): "Safety Warning: Tableware producers must test all finished ware to establish dinnerware status, due to possible variations in firing temperature and contamination." This warning does not appear on brushing glazes, even the reactive metal-saturated ones that potters and hobbyists use!
Glossary	Food Safe Be skeptical of claims of food safety from potters who cannot explain or demonstrate why. Investigate the basis of manufacturer claims and labelling and the actual use to which their products are put.

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