Veegum CER Saturated suspension

This is the most viscous suspension we can make using hot water and a propeller mixer - 300ml water with 13.25g Veegum CER. In glazes having low clay content adding this gels the slurry, enabling higher water content to improve its brushing properties and slow down drying. In slurries having plenty of clay pure CMC gum is usually better (unless a high-water-content slurry is needed). Of course, keep in mind that anything with CMC gum can be subject to microbial attack.

Related Pictures

You may know Veegum T but do you know VeeGum CER?

Attempts to use a glaze that is too thick

The glaze in this jar was 'goop', impossible to paint on because it was too viscous. And it dried way too fast. Laguna mentions adding water so I measured the specific gravity (SG): 1.7. That is super-high, it took a 125cc addition to bring it down to 1.5, but it was still thick, dried even faster, and brushing it on evenly was even harder. It was not obvious what to do next. It needed a lot more water (1.3-1.35 SG is normal for multi-layer application of low SG glazes), adding CMC gum and enough water to do that would produce an unusable watery and sticky slurry. Veegum CER to the rescue! It is a 50:50 mix of CMC gum and Veegum T. The former slows drying and hardens, the latter gels. So it can simply be added until the painting properties are right. And, a Veegum CER solution is easier to handle than one of CMC gum. The brushing properties are just right, it gels nicely on standing and stays in place on verticals. CER is also good for highly fritted dipping glazes or others lacking in clay content (otherwise CMC might still be better).

Control gel using Veegum, brushing properties with CMC gum

This is G1214Z1 brushing glaze (with 5% titanium added). For a 340g powder batch (to get a pint) my initial target is 5g CMC gum and 5g Veegum. CMC controls drying speed and Veegum the amount of gelling. I first mix the CMC with the powder and shake the whole batch in a plastic bag. Then I add it all to 440g of water in the blender jar and mix it well (making sure no agglomerates remain (stage 1). Stage 2 is adding the VeeGum slowly, while high-speed blender-mixing, this is important because it enables tuning the degree of gel (which cannot be predicted). Because this recipe has little clay, it took all 5g of Veegum without overgelling (the entire mass moved freely in the mixer jar). But it did gel overnight (so 4g would be better next time). By contrast, it is the brushing behavior that demonstrates whether the amount of CMC is right. Not enough and coats dry too fast and go on too thick. Too much and it dries too slowly and too many coats are needed.

Links

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 agent in slurries.
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.

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