Mocha Diffusoin

[Lawrence Weathers]

Hi
I'm trying to learn how to do mocha diffusion. I read your description along with a number of others on the web. However, I'm not having any luck getting the dendrite pattern. I will try very a lot of things and nothing seems to make much difference.

This is what I've tried:

1. Slip made of Tennessee ball clay
2. Robin Hopper's diffusion slip: (ball 75, spar 5, silica 10, epk 10) plus I add 5 3134 and 10 RIO
3. adding hardwood ash, or sodium silicate, or Calcium nitrite to the above slips

I've used thick and thin solutions of cobalt carbonate and ordinary vinegar or apple cider vinegar.

I've tried using in both horizontally and vertically on my leather hard G6 mix clay.

The very best I've done is to get some almost microscopic dendrites on the edge of my dribbles.

Also, in a CAD article Robin Hopper gives the following recipe  for diffusion slip

ball clay   75,

Feldsspar  5,

silica       10,

Kaolin      10

Does anyone know what kind of ball clay and feldspar one should use?

I would appreciate any advice or guidance you can give me in debugging this.

Thanks

Larry

 

[tony remington]

Hi I have just come across this article about ten years too late. I am the Tony Remington referred to in this article. I used to make mocha ware back in the 1980/90s I did a short piece for local TV showing me making and decorating mocha pot. During the filming I talked through  the process of decoration and said the mocha tea I used was an alkaline solution, this was a nervousness mistake I made during filming what I should have said it was in fact acidic, but having no editorial rights I couldn’t change it and it was broadcast. I also mentioned the oxide I used to colour the tea and that was edited out.

So to put the record straight I used a half ounce of light tobacco which I boiled in a half pint of water. One the tea was cold I added cobalt oxide to give the colour. I tried other oxides manganese, red and black iron, but cobalt gave the best result. I tried many slips but settled on a porcelain clay with no additions that gave enough resistance as the juice was applied to the pot allowing the trees to form in a control manner. A lot of the slips I tried gave mixed results, the tea would run straight down the pot with no feathering. I made mocha ware for the best part of ten years using this technique with few issues. Hope that clears this up

Norm Stuart said:

It's obvious the "Mocha Staining" created by Tony Remington, the potter in the video, looks exactly like Staffordshire Mocha ware with the dendritic pattern first produce in the 1780s. An 1800s piece is shown below.

It would appear no one can explain how the channels are formed, nor even where the color comes from after a kiln firing.

Tony Remington says he simply uses boiled tobacco (without iron, manganese or black Mason stain). He claims the original Staffordshire Mocha potters also added stale urine and turpentine. He claims the mocha solution creates the channels due to its alkalinity. An alkaline solution deflocculates clay slip.

Richard Ruckert says the acidity of vinegar works but not as well, and adds black Mason stain, but vinegar would flocculate the the slip - the reverse of boiled tobacco.

Other texts on "Mocha ware" ascribe the channeling effect to the differences in the surface tension, called the Marangoni Effect, which you see when adding a surfactant, like dish washing detergent, to water and all of the other solids on the surface of the water move away from the surfactant. - Marangoni Effect  If this were the case we could create the channels using diluted Tide detergent.

Other sources say the channels are due to the capillary effect.

The traditional ingredients don't seem to add much helpful information.

Stale urine is certainly alkaline from ammonia (converted from urea into ammonia and carbonate ions);

Boiled tobacco  pH ranges from 4.5 which is as slightly acidic as black coffee to 8.0 which is slightly alkaline like sea water.

Turpentine (not having hydrogen ions) doesn't have a pH.

Looking at the chemistry of tobacco in this PDF, there doesn't appear to be anything which would cause a dark color after being fired in a kiln, but there are fluxes - calcium, potassium, magnesium and phosphorous.

Tobacco chemistry - second page of PDF

Obviously something like manganese has to be added to the boiled tobacco, but neither Tony Remington nor historic records admit to this.

This decorating process seems to be a deliberate mystery with no obvious explanation.

Staffordshire Mocha ware from the mid 1800s

Based on the comments in the video, the shorter cactus-like dendrites on the left were probably added after the slip was drier.

[Norm Stuart]

Tony Remington, thanks so much for providing your original recipe

"A half ounce of light tobacco which I boiled in a half pint of water.

Once the tea was cold I added cobalt oxide to give the color."

You say the resulting solution is acidic.

The reported aqueous pH of natural tobacco ranges from 5.7 (as slightly acidic as yeast or ground ginger), to 7.8 (slightly more alkaline than Tea with 7.0 being neutral).

[tony remington]

When I say tea I mean the tobacco infusion was called the “mocha tea” 

  Tony

Norm Stuart said:

Tony Remington, thanks so much for providing your original recipe

"A half ounce of light tobacco which I boiled in a half pint of water.

Once the tea was cold I added cobalt oxide to give the color."

You say the resulting solution is acidic.

The reported aqueous pH of natural tobacco ranges from 5.7 (as slightly acidic as yeast or ground ginger), to 7.8 (slightly more alkaline than Tea with 7.0 being neutral).

[tony remington]

https://youtu.be/ynSOt6RjSA4?si=Kgnixcg_mf8g_s8H

in this vid I say the mocha juice I used to decorate my pots is alkaline, that was a nervous mistake during filming, it is in fact acidic.

[Norm Stuart]

Apply the mocha quickly after applying the slip to the pot, otherwise you don't get the dendrite branching.

Tony - this key step you mention in the original video is what many of us were missing.

Half of the chemistry is in the slip. Thanks

[tony remington]

I tried many slips Norm but I settled on a porcelain clay no additives I used it at a single cream sort of consistency, you need a slip with a bit of resistance in the slip otherwise the tea runs straight down the pot. Plus as you stated once the pot has been dipped get the tea on. When I was filming the vid I had to slow it down because the cameraman couldn’t keep up with me. 

Norm Stuart said:

Apply the mocha quickly after applying the slip to the pot, otherwise you don't get the dendrite branching.

Tony - this key step you mention in the original video is what many of us were missing.

Half of the chemistry is in the slip. Thanks