Brushing glazes on large pottery items is surprisingly practical

I applied this transparent inside and out on both bisque and bone-dry ware using only a small brush (of course a larger one or a fan brush would be better). I have done up to 35 lb bowls this way. This is not a commercial brushing glaze, it is a dipping glaze that we mix ourselves: G1947U. We add 10g CMC gum powder to one liter of a water-reduced version of the slurry. Blender mixing makes it possible to mix in the powdered gum and tune water content for the best brushing experience. The gum slows down the drying speed dramatically so there is plenty of time to brush it into place (while the wheel is turning). The gum also greatly increases the cohesion, enabling pouring it without drips, even in a long thin stream. Many pieces were done like this in recent kiln loads (including application onto a leather-hard 40-inch tall vase), the evenness of coverage was the best I have ever gotten (of any technique).

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Add CMC gum to a dipping glaze slurry for brushing

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The outsides of these reduction-fired bean-pots are a unique challenge to glaze evenly and drip-free using dipping or pouring (also, a much thinner layer is needed inside the flange). A gummed brushing glaze is a solution. But how can one convert a cup of dipping glaze into a brushing glaze? CMC gum powder - it slows down drying and imparts brushing properties. Since our dipping glazes are about 50:50 water:powder, I blender-mixed 3.75g CMC gum powder into 1000g of slurry to get ~0.75% concentration (depending on your mixer it might require more). Triple-layer brush-glazing this piece takes about five minutes. I use two brush types (fan and hake) and different techniques for each zone. It dries really hard. If the gum over-thins your glaze, a water-reduced version is needed. Assuming it has settled somewhat pour off or sponge off some of the water and add the CMC gum to that. Don’t forget, it has to be blender mixed.

Glazing large bowls inside-and-out using brushing glaze

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This wheel-thrown bowl is large, heavy and thick walled. There are pouring techniques to apply different colored dipping glazes to the inside and out but they are cumbersome and slow. It turns out that the hobbyist way of glazing is actually better - by brushing. I make these 500ml jars of brushing glaze and tune the percentage of gums to get the painting consistency and drying time best for me. Applying multiple coats by brush took only a few minutes and no wax resist or any other tools were needed. And it was easy to meet the two glazes in a straight line at the rim using the brush. The inside glaze is G2936B and outside is G2926B.

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

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Let's make a low SG version of G2934BL, totally DIY. Weigh out a 340g batch of dipping glaze powder. Include 5g Veegum (to gel the slurry to enable more than normal water) and 5g CMC gum (to slow drying and impart brushing properties). Measure 440g of water initially (adjusting later if needed). Shake-mix all the powder in a plastic bag. Pour it into the water, which is blender mixing on low speed, and finish with 20 seconds on high speed. This just fills a 500ml jar. In subsequent batches, I adjust the Veegum for more or less gel, the CMC for slower or faster drying and the water amount for thicker or thinner painted layers. Later I also assess whether the CMC gum is being degraded by microbial attack - often evident if the slurry thins and loses its gel. Dipping glaze recipes can and do respond differently to the gums. Those having little clay content work well (e.g. reactive and crystalline glazes). If bentonite is present it is often best to leave it out. Recipes having high percentages of ball clay or kaolin might work best with less Veegum. Keeping good notes (with pictures) is essential to reach the objective here: Good brushing properties. We always use code-numbering (in our group account at Insight-live.com) and write those on the jars and test pieces. This is so worthwhile doing that I make quality custom labels for each jar!

Videos

Links

URLs	https://youtu.be/-f-skGLVyMg Youtube Video: Brush Glazing Large Pieces By blender-mixing 10 grams of CMC gum into a liter of my standard dipping glaze I can apply it to the insides and outsides of large bowls quickly and evenly. This is better than any other method I have used.

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