Mocha Diffusion Mugs

Mocha Ware

Mochaware derives its name from stone that was originally first discovered around Mecca. We think the name underwent a change by the time the actual mocha diffusion process came to be used in the mid 18th century in English production potteries. What’s most interesting about this technique is the lack of historical recipes. We do know a few things:

  • The technique began to be used circa 1750
  • It was used on earthenware pottery (fired at a much lower temperature than our own stoneware)
  • The pots typically had 4 trees and some brown banding and were brown and off-white in coloring
  • How these ingredients were used remains somewhat of a mystery, but they included urine, turpentine and tobacco
  • The nature of a production studio lends itself to mocha decorating techniques because hundreds of pots can be rapidly decorated, and though there may be a few losses, they wouldn’t have a major impact on the financial outcome of such a factory.

We first discovered some information about mochaware at the Ontario Potters’ Association convention in Ottawa in 1981. It intrigued us both. However, our first experiments quickly taught us that firing mochaware at our higher temperatures needed some thorough adjusting of the tea we created to form the lovely dendritic tree patterns. NO, we don’t use either urine or turpentine in our mocha tea… but we sure do use tobacco. In fact, we try to get the cheapest and nastiest pipe tobacco we can find to make this putrid tea. When it’s applied to a slipped pot, the tea quickly disperses, “treeing” out as it goes. We can tell you that the slip we apply to our almost dry pots needs to stay glossy (moist) while the tea does its trick. If the pot is too dry, and the slip likewise, the tea runs off in straight ugly lines. If the pot is too wet, the “treeing” does not stop, and these crazy uncontrolled trees will branch up over the rim of the piece totally spoiling the landscape effect we’re after. The tea is highly acidic, the slip highly alkaline and both need to be in perfect condition to create their rapid magic.

Mugs and Tumblers with Mocha Landscapes Ready to Fire
Mugs and Tumblers with Mocha Landscapes Ready to Fire

It may form the fastest decorating technique in our studio, but it’s far from guaranteed to bring successful results each and every time. Perhaps because we’re such a small studio, we never have enough pots around to hazard wasting a half-dozen or so in finding whether our tea is in its perfect state to guarantee success. Over the years, however, we’ve loved making these beautiful pieces that we feel celebrate our arboreal surroundings.

2 thoughts on “Mocha Ware

  1. Hi Jo and Vic, I have been potting for over 3 years ( I know Im new ), and it seems that this time of year is when its a slam from everyone but I still hold to atleast one thing that I want to master. Now I have been trying to find everything I can on the net about mochware and so far I found finally one recipie for a slip and thanks to you two I finally have a better answer on the tea itself. Im gonna find the pipe tobacco and use apple cidar vinager but I was hoping you two can help me with this slip. The recipie is: Feldspar 5%, Ball Clay 75%, Kaolin 10% and Silica (flint) 10%. Now I so know this will take a long time and many distroyed pieces to get right (and even then Im sure I will lose a lot of work for the inbetween stuff) but I love the look and the fact that its a process thats old and kinda mysterious 🙂
    This year is when I really started to put my foot in the ring for glazing, but with slips for some reason Im still having a hard time with understanding how to make them. I was also wondering, how in the hell do you glaze it?? I am amazed to see that you can do it even with everyone saying it can’t be done over cone 4, so I am assuming yours is around there. I use cone 6 clay and really, I don’t want to deviate. So here is the other question, If it can’t e clear glazed over the pattern can I still glaze the inside of whatever the piece is. I know that sounds stupid but I have come accross the weirdest results from things before so anything that is possible in another dimension is always possible with pottery, or maybe its just me! LOL
    I know telling other people these things can be your big secret so I do understand if you don’t want to share, Im in two guilds so I know how some people can be, and sometimes its very understandable. I am searching so much because of no knowledge for mochaware is around my guild members. They say its hard and if you go to Sheridan with a lucky teacher you might get to try it. But Im a long way from that yet! SO in my closing I do have to say, out of all the pieces I have been looking at the one that is your bacjground on this page is freakin awesome! How it goes from top to bottom is so amazing to look at it makes you wonder what you could do, but I swear Im still trying to see if its three glazes or two, the over lap throws me but I love it.
    Thanks for any help and if you two are ever out this way (burlington, ontario) Please contact me. I would love for you two to come and show my guild a thing or two.
    Keep on potting!
    Katherine Ford

    1. Hi Katherine,

      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.

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