Willemite Ceramics

handmade by

Evan

Cornish-Keefe


Mocha Diffusion aka Dendritic Slip

Mocha Diffusion aka Dendritic Slip

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I first heard of this technique about 5 years ago, and seeing the detailed branching patterns that can form in seconds, I was immediately was very interested. I think I first saw mention of this technique in an article by Robbin Hopper, and then I found an article by Jeff Zamek with a little more detail on this technique.

Mocha Diffusion is named after a type of stone, called a Mocha Stone, originating in Mecca this stone is a type of moss agate with naturally occuring dendritic patterns which formed through it. Dendritic formations like to happen naturally all over the place, in various minerals, occasionally in glazes, water running through sand at the beach, and your brain has something like 100 billion neurons each one having dendrites. The image used in the thumbnail of this post shows a piece of natural dendritiic druzy quartz that a friend gave to me, in front of a “landscape tile” I made with this Mocha Diffusion technique.

A rare and mysterious dendrite shaped crystal in a glaze.

A rare and mysterious dendrite shaped crystal in a glaze.

It took about 3 years of quite unfortunate experiments to even start getting decent results with this technique, and still today I find it unpredictable and much more complicated than it appears. I saw some images of pots made 200 years ago in England with great examples of Mocha Diffusion, which showed me how well this technique can result. I wasn’t sure what to try and the theory that many people claim, that this is a pH reaction between between a somewhat alkaline clay slurry and an acidic colorant wash hasn’t seemed to hold true. At this point I question whether there’s little or any truth to that claim.

So far I’ve found that the simplest results use a mixture of tobacco and water with a mason stain of any color. A drop of this mixture is applied to a still liquid clay slip. It seems best if the slip is fairly plastic such as for a throwing clay body, and ideally not deflocculated although the technique can still be done with a casting slip (deflocculated and low plasticity) tho the colorant mixture may need altering for that to work well. There are better mixtures that do not use tobacco, but they’re seeming more finicky and I’ve decided to develop those more before sharing.

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On my Gallery page I’ll post some videos of this technique, I think it’s fun to watch the dendrites form in just a few seconds.

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Crystalline Glazes

Crystalline Glazes

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