Control gel by adding Veegum as the glaze is mixing

This is G1214Z1 brushing glaze (it has 5% titanium added). For a 340g powder batch (to get a pint) my target is 5g CMC gum and 5g Veegum. CMC controls drying speed and Veegum the amount of gelling. I already mixed the CMC with the powder and shook the whole batch in a plastic bag. Then I added it all to 440g of water in the blender jar and mixed it really well, being sure no agglomerates remained (that was stage 1). Stage 2 is adding the VeeGum slowly, while blender mixing on high speed, this enables tuning the degree of gel. Because this recipe has little clay, it took all 5g of Veegum without gelling too much (too much means the entire mass is not moving freely in the mixer jar). This recipe could have taken a little more CMC to slow down drying a bit (this amount enabled applying three coats to a bisqued piece in only a couple of minutes but it did not brush on quite as nicely as it could have). Sure enough, it gelled more overnight so the next time I used 4 grams of Veegum (each recipe has its own optimal amount). Both of these gums are very difficult to mix into water without agglomerates forming, the high water content enabled the stage 1 slurry to be mobile enough in the mixer jar that the blade has access to all particle surfaces. And it enables mixing in enough stage 2 VeeGum to achieve a consistency that will never settle out.

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

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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

Materials	CMC Gum CMC gum is indispensable for many types of ceramic glazes. It is a glue and is mainly used to slow drying and improve adhesion and dry hardness.
Materials	Veegum A clay of incredibly small particle size. It has the highest plasticity of any known clay and acts as a suspending and gelling in slurries.
Glossary	Micro Organisms Ceramic glazes and clay bodies can host micro organisms. They can be just a nuisance, a source of worry or can render a product useless. What should you do?
Glossary	Rheology In ceramics, this term refers to the flow and gel properties of a glaze or body suspension (made from water and mineral powders, with possible additives, deflocculants, modifiers).
Glossary	Brushing Glaze Hobbyists and increasing numbers of potters use commercial paint-on glazes. It's convenient, there are lots of visual effects. There are also issues compared to dipping glazes. You can also make your own.

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