My Mochaware is based on a white-firing body, M-370 from Plainsman Clay, which I’ve used for 6 years now. Good results can also be had using Laguna cone 5 B-Mix. I fire to cone 6, 1200 C using computer=fired kilns.
Let’s imagine a fresh Mocha session…two weeks before I make the vessels I prepare the slip and the tea.
Boil 100 grams of cheap and nasty pipe tobacco in two litres of waterr, rapid roll until the liquid has reduced to one litre…it helps to have a a flat disc with holes in it to keep the tobacco fully immersed. I then shut off the pan and allow the stuff to sit for at least 7 days by which time there will be a patch of mould on the surface…peel off the mould and pass the juice through a fine strainer to capture the liquor and store until you are ready to test it with your slip.

I would like to point out that I apply my Mocha on bone-dry ware. The clays I use have an outrageous amount of shrinkage, due to their fine particle structure…about 12 – 14 % linear shrinkage from wet to finished product. At the bone-dry state, the clay has shrunk to about 6%. The application of wet body slip on a wet or leather-hard piece would be just fine since the clay and slip can shrink together. On a bone dry piece, however, the slip must shrink more than the clay on which it is applied. The stress results in surface cracks or even peeling right off…this may not appear until the final fire, phenomenon known as shelling. You must, therefore, adjust the clay content of your slip to suit the clay body you use by substituting non-clay or low-clay materials.
Slip is passed through 40, 60, and finally 80 mesh sieves to a specific gravity target of 1.450. Keep the bucket clean, i.e. wiped with a wet sponge upon completion to prevent dry flaking on the sides of the bucket.

For the tea, pour 250 ml. of juice into a wide-bottomed container and add your choice of colourants. This is where you need to judge the quantity for yourself…you can test by dipping a plastic tile into the slip and
use a brush to apply a stroke or two of tea. Hold the piece upside down to gauge ‘ full frame ‘ growth and adjust the strength as required to get a nice crsp image. Bear in mind that the plastic stays wet unlike a dry piece of clay which allows you only 10- 15 seconds to do your decoration….once the moisture is absorbed the trees will stop growing.

Dry the pieces thoroughly and bisque fire to cone 04, 1040 C – ish.

As for the transparent glaze, see Ron Roy / john Hesselberth’s ‘Mastering cone 6 Glazes……liner glaze applied at specific gravity of 1.500.

I hope this will help… to achieve success with mocha diffusion truly requires a patient journey filled with experiments.

Vic

PS… If your guild is interested in a workshop, I’d be agreeable to doing one of those in the spring or summer… I could combine the workshop with a visit to family in Waterloo. We charge $400 per day for our workshops, and have conducted masters’ workshops in the BC lower mainland and on Vancouver Island.