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

 

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Hi Lawrence,

I've used mocha diffusion. My challenge is controlling the dentrites. They tend to go beyond the lip of the cup, and at least some were tall cups. 

I've used apple cider vinegar, but found the tobacco recipe more effective. I think the most effective colorant is Mason black. I think the number is 6600. Cobalt should be ok, but the particle size maybe to large to move through the slip effectively. 

The most important part is timing. After dipping the ware into the slip, and slip from your throwing scraps should be fine if they are light colored, and the Hopper recipe also works. Here is the "tea" recipe I use. tobacco is chewing long cut. I don't chew tobacco. nd, i sub out mag di for mason stain. here is a youtube link 

https://www.youtube.com/watch?v=ynSOt6RjSA4&list=PLq3guUCyxssfk...

good luck 

Richard

1 ounce of tobacco
1 pint of warm water
1 1/4 ounce of iron or manganese.
let steep overnight, strain off tobacco

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.

Hi Larry, I have been watching Kevin Kowalski on Periscope. He has been showing some interesting techniques with mocha diffusion. He also has all the recipes listed on his website; http://kevinkowalskipottery.weebly.com/mocha-diffusion.html

I use Robin Hopper's slip recipe in my studio. We did some tests with the acid for the mocha diffusion, trying apple cider vinegar, lemon juice and urine.... with black mason stain in each. The urine worked much better than anything else, until one of my students brought in some female horse urine. I believe I saw a video of Robin mentioning that this worked best... and it does. Another key to success may be the timing, I apply the mocha diffusion mixture almost immediately after pouring on the slip. I get some terrific dendrite patterns. If your mocha patterns are too large for your slip area, remove some of the mocha diffusion mixture from the brush before applying to the slip.

Attachments:

In my opinion one can obtain excellent Mocha diffusion without all that hassle of tobacco tea matching acidity and so on by just using a drop of household detergent. I made excellent diffusions adding a drop of TWEEN 80 ( a more 'scientific' kind of detergent) . Unfortunately I discarded pictures where I compared Tobacco, cider vinegar, and Tween 80. Tween 80 works always. Forget tobacco tea, vinegar and whatever complex concoctions.



Daniel Spruyt said:

In my opinion one can obtain excellent Mocha diffusion without all that hassle of tobacco tea matching acidity and so on by just using a drop of household detergent. I made excellent diffusions adding a drop of TWEEN 80 ( a more 'scientific' kind of detergent) . Unfortunately I discarded pictures where I compared Tobacco, cider vinegar, and Tween 80. Tween 80 works always. Forget tobacco tea, vinegar and whatever complex concoctions.



John P. Langer said:


Daniel Spruyt said:

In my opinion one can obtain excellent Mocha diffusion without all that hassle of tobacco tea matching acidity and so on by just using a drop of household detergent. I made excellent diffusions adding a drop of TWEEN 80 ( a more 'scientific' kind of detergent) . Unfortunately I discarded pictures where I compared Tobacco, cider vinegar, and Tween 80. Tween 80 works always. Forget tobacco tea, vinegar and whatever complex concoctions.

Dan, what did you add the tween 80 to? Thanks, John Langer

All you would add to the Tween-80 is a colorant like black mason stain, iron oxide, or manganese dioxide.  The mocha colors in tobacco all vaporize in the kiln leaving no color.

Tween-80 is a liquid detergent used in biochem labs to extract DNA protein from cells, a nonionic detergent without any foaming/sudsing agents.  -  http://www.sigmaaldrich.com/catalog/product/sigma/p4780

Tween-80 is relatively costly so I'd suggest pure liquid castile soap without added fragrances etc. It is a liquid nonionic surfactant made from olive oil which is readily obtainable. If it's too thick you simply dilute it with water, or distilled water to avoid adding ions.  Use pure castille soap without added glycerin or other ingredients which eill change how it interacts with the wet clay.

Laundry detergents like Tide have added foaming agents, deflocculants to remove calcium and magnesium, perfumes and enzymes. Pure liquid castile soap is just the nonionic surfactant, olive oil reacted with an alkalai.

Thanks Norm. I don't know that I have seen the tween 80 around. I may just try another surfactant. John

To the stain or oxide suspension I use approx 1 drop of detergent for 2-3 ml of stain suspension

John P. Langer said:

Dan, what did you add the tween 80 to? Thanks, John Langer
Keep in mind that the slip on the pot must be fluid and still very wet

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