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docweathers

Robin Hopper's Mocha Diffusion-Base Slip

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in the article of Robin Hopper demonstrating mocha diffusion, he gives the following formula for his base slip.

 

Feldspar       5%

Ball Clay     75%

Kaolin         10%

Silica           10%

 

 

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

 

Also I'm trying to get mocha diffusion to work and having very little success

 

  I read a number of descriptions, including Robin's on the web. However, I'm not having any luck getting the dendrite pattern. I have 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. One of 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, or amonia 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.
 
I would appreciate any advice or guidance you can give me in debugging this.
 
Thanks
 
Larry

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Feldspar 5%

Ball Clay 75%

Kaolin 10%

Silica 10%

 

 

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

 

I cannot say exactly but if I where making this I would use

potash feldspar like Custar feldspar

for ball clay it would be om4-which is Kentucky ball clay-your Tennessee ball clay is so close it would be fine

the EPK for me would be Edgars Plastic Kaolin-the standard for EPK

I use 325 grind silica as well.

I cannot help yop on the rest as I like my mocka in a mug served hot.

Mark

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Hi Mark

 

Thanks for the suggestions.

 

Since I posted this, I mixed up some of the slip with custer feldspar,, EPK, and 325 silica.... As well as also trying it with minspar 200. I still can't get the diffusion to work with either feldspar

 

I must be doing something else wrong but I've run out of ideas of what to test.

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Larry;

I have not done this myself, but i have seen the technique done in England and the Southern states.

you dip your leatherhard pot in white slip.

When the sheen has gone off, you pour on tobacco juice made from old cigarette butts. This is the secret ingredient-very acidic.

Remember, i have not practised this myself, but I am very sure that this is what they used.

TJR.

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Min's the one on this.

Seem to remember from reading that the slip has to be quite alkaline.

The wetness when adding hte acidic stain would be crucial as well.

Min uses this technique , have you done a search on this.

Bit of soda ashas an additive.??

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I will have to try the tobacco and the soda ash. If Min doesn't respond to this thread I will PM.

 

I did try letting the sheen go off of the base slip before I put the stained vinegar on it. Absolutely nothing happens when I do that. I don't even have a little fragment dendrites around the edge of my blobs. In the Robin Hopper Video, it looks like the base slip is very wet.

 

Thanks

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I will have to try the tobacco and the soda ash. If Min doesn't respond to this thread I will PM.

 

I did try letting the sheen go off of the base slip before I put the stained vinegar on it. Absolutely nothing happens when I do that. I don't even have a little fragment dendrites around the edge of my blobs. In the Robin Hopper Video, it looks like the base slip is very wet.

 

Thanks

I think you are right now that I think of it. i think the slip has to be wet. you put some kind of stain in the tobacco juice like iron ox., and it forms these tree like structures. Saw it done about 20 years ago, so i may not have it right, but I am very sure that it was tobacco that they used. they were pretty cagey about it at the pottery I visited in the states, calling it a rare herb. i laughed, because I knew tobacco when I saw it.

TJR.

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it is tobacco.  i did this years ago.  the slip is applied and while wet a small paintbrush with the tobacco (can't remember the wetting ingredient) is touched lightly to the edge of the slip and it will grow to look like a tree.  i have the recipe in my glaze book and will look it up for you.  

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larry, there is a website, pottery-magic.com which shows it.  it appears that any acidic liquid is ok to put the tobacco in.  can't get into the studio to get the glaze book tonight.

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My copy/paste has stopped working on my mouse.  If you go to Robbin Hoppers blog: rhrising.blogspot.com to his post dated March 11, 2013, Mr. Hopper reviews his process for mocha diffusion.  Maybe this will help you. He says he used apple-cider vineger.  Hope this helps.

 

 

 

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doc, sorry, i do not have anything about mocha diffusion in my glaze book.  i read all the things noted in the many responses above and see that the general opinion of potters who have experience in this use boiled tobacco and apple cider vinegar. having wet slip freshly applied and touching a brush to the edge results in the tree-like forms that spread out from the spot that is touched.  if you read the questions under the video, robin answers the questions you have asked re the specific feldspar, etc..

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 I got it to work by adding a little Epsom salts to the Tea. What a relief since I had tried just about everything else I could think of. I tried well water, distilled water, apple cider vinegar, regular vinegar, soda feldspar, potassium feldspar, OEM 4, Tennessee ball clay, Ammonia etc. I just figured that if the tea needed to be flocculated, Epsom salts was a good candidate to do that. Now I just need to work out the proportions for different colors and densities of tea.  

 

Thanks for all of these suggestions

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