4 cell drying batt

I am currently doing the Curtis Benzle 'Colored Clay' course with TeachinArt: https://www.teachinart.com/colored-clay. It is a very interesting course and I thoroughly recommend it. Curtis recommends preparing coloured clay from the dry ingredients in order to have precise control over the ratio of stain to clay and to enable a particular colour mix to be replicated. It is also a somewhat cleaner process than mixing the stain direct into hydrated clay.

The dry ingredients are mixed with water and left to hydrate, producing a sloppy slip about the consistency of Greek Yoghurt. This can be stored in a sealed container until required.

At this stage, it is too wet to use as coloured clay. In order to reduce the water content to the requisite level, it is decanted into a plaster drying batt where it is left for several hours.

This is a summary of the process I followed to make a 4 cell drying batt.

My inspiration was the 8 cell drying batt below. I could not find a commercial supplier of anything similar and I suspect that it was home made.

8 cells seemed to be rather more than I would need, so I initially decided on a 6 cell batt, which ended up looking like this:

This is reasonably satisfactory, and certainly does the job for which it was intended. However I learned the following lessons during the process:

The 'walls' which I was using to hold in the wet plaster sprang a leak, which resulted in a small but messy loss of plaster.

The positive hemisphere moulds which I used to create the cells were quite hard to extract, once the plaster had cured.
The cells are a little too close together and to the edges, giving fairly thin walls which could result in differential drying rates.
The mould is deeper than it needs to be resulting in an excessivley heavy mould. The finished mould weighs in at 8kg.
I ended up with a few air bubble voids in a couple of the cells.

Making the hemispheres

The first step was to cast 4 x hemispheres. I used a 100mm 2 part round silicone soap making mould, purchased on eBay, for this. I mixed 300g plaster and 210ml water for each hemisphere.

After about 30 minutes, the plaster had set and the hemisphere could be eased out of the silicone mould.

Making the mould casing

The next step was to build the casing for the mould. I used a sheet of melamine faced chipboard as the base. I then placed the 4 hemispheres face down on the base board with a 2.5cm space between each hemisphere. I drew a rectangle around the hemispheres, also with a 2.5cm border.

To be continued ...