Mocha slip

[B.J.]

I'm going to try the mocha or dendritic glaze process. I usually fire to cone 6. 

I found a slip recipe that I want to use, but I have a few questions about it.

Feldspar                  5%

Ball Clay.                75%

Kaolin.                      10%

Silica.                         10%

Where I buy my supplies they have G200EU, and Minspar feldspar. C & C Spinks, Kentucky OM4, Kentucky Stone, Old Hickory #5, Tennessee SGP1, ball clay. Amorphous, Carbide FFF, #90, #53, silica.

Does anyone know which feldspar, ball clay, and silica I should use?

Any help is appreciated! 

Bonnie

[Min]

Hi Bonnie and welcome to the forum.

This looks like Hopper's recipe for mocha diffusion slip. When I used to do a lot of this I used custer spar so G200EU would be a good current source for the spar, for ball clay I used OM4, EPK for the kaolin and 200 mesh silica. I don't think it's really critical which spar, kaolin or silica you use, main thing is the ball clay. You are just going for as alkaline a slip as you can get, haven't used other ball clays so can't comment on how they would work. I've also used Laguna B-Mix as the base instead of Hopper's recipe, it works well too. A little tip, when you are mixing the "tea"  on add a drop of dishwashing liquid to it, makes it work even better.

[B.J.]

Thanks Min!

That clears up alot of confusion for me. I guessed right on 2 of the 4 ingredients. I've only mixed up a clear raku glaze before (which is super easy). This will be a bit more difficult, but I'm determined to make it work!

Thanks so much for the welcome!

[PeterH]

Some previous threads on Mocha

 

PS Ceramic Arts Network search
https://ceramicartsnetwork.org/search-results?keywords=mocha

Edited June 17 by PeterH

[Magnolia Mud Research]

Robin Hopper (aka GRASS): wrights about mocha: 
https://rhrising.blogspot.com/search?q=mocha+ 

part of his discussion of MOCHA is:

Monday, March 11, 2013
MOCHA DIFFUSIONS
one of his recipes:
ROBIN'S UBIQUITOUS SLIP
ANY BALL CLAY  75
ANY KAOLIN       10
SILICA                      10
ANY FELDSPAR    5
TOTAL                   100

TO DEFLOCCULATE THIS SLIP SO THAT IT BECOMES FLUID WITH LESS WATER. ADD 1% SODIUM SILICATE AND/OR 1% SODA ASH

THERE ARE MANY VARIETIES OF SLIP TRAILER.  THE ONES I LIKE BEST ARE RUBBER BULB TYPE CHILDREN'S ENEMA BOTTLES WITH DETACHABLE TIPS, OR BULB TRAILER SETS WITH VARIABLE SIZED TIPS FROM TUCKER'S CERAMIC SUPPLIES, ONTARIO, CANADA

 

LT

[Callie Beller Diesel]

I have a co-worker who wants to try this with one of her classes, and I would love any pointers on getting the consistency of both slip and tea right. I’ve got the slip mixed, but I haven’t deflocculated it or anything. Would darvan do the same, or does it have to be soda ash or silicate for the ph?

Also, I have heard that different acids give different dendrite patterns. I have white vinegar and citric acid on hand. Does anyone have any other favourites?

[Marilyn T]

Hi Callie,

I use the Robin Hopper slip at 1.35 SG (without deflocculating and sieved through 60 mesh)  and put it on a leather hard vessel  (just after I put the handles on).  The wetter the clay is, the more time you will have for the chemical reaction to occur.  

I tried all types of acids but the one I liked the most was malt vinegar at 30% Mason Stain 6650 in 100 ml vinegar..  I see lately some people are using nail polish remover but I wouldn't use that with school students.   

[Min]

+1 for vinegar, I used apple cider.

When I saw Hopper demoing mocha diffusion  he was using apple cider vinegar so I went with that. At the time he wasn't defloccing the slip, I never found a need to defloc it. 

I've noticed there is an adjusted recipe for slip for using at lower temps, ^2 and under, as the above recipe can result in glazes crazing for low cones. There is mention of using a defloc or Bentone MA in the adjusted slip recipe f the lower plasticity of it necessitates it. Recipe below from this article for the ^2 and lower slip. 

 

[Callie Beller Diesel]

Ok. Here are results with the Robin Hopper slip. The reddish tea is iron and manganese in citric acid with a drop of dish soap, and the green is mason stain in vinegar, again with the dish soap. 
I didn’t measure the slip’s SG, but it’s about the consistency of whipping cream. 
https://www.instagram.com/reel/C8a3EgkPjn9/?igsh=MXZmeDVsOXZiZm5lMA==

 

(if the link doesn’t open on a desktop, let me know and I’ll get a better one for you.)

[Min]

Link worked for me Callie.

Does the glaze you will be using dissolve iron? I think there might be too much stain in your green tea. I found with thinner walled pots I needed to use a thinner slip or else the slip would collapse the pot.

It's fun isn't it?

[Dick White]

Regarding deflocculating the slip to make it thinner with less water, do not use Darvan. Darvan is a fine deflocculant for many things, but the reaction that causes the starburst effect in mocha diffusion is due to the acidic "tea" vs. the alkaline slip. The slip is already slightly alkaline, so deflocculating with a touch of sodium silicate or soda ash adds to the alkalinity of the slip. Darvan deflocculates by a different mechanism, so may not give the same outcome as the sodium items.

[Babs]

10 hours ago, Min said:

Link worked for me Callie.

Does the glaze you will be using dissolve iron? I think there might be too much stain in your green tea. I found with thinner walled pots I needed to use a thinner slip or else the slip would collapse the pot.

It's fun isn't it?

What would be a suitable C 5/6 glaze recipe be to keep the mocha pattern distinct?

[Min]

5 hours ago, Babs said:

What would be a suitable C 5/6 glaze recipe be to keep the mocha pattern distinct?

I don't have a clear that doesn't dissolve iron to some degree in oxidation firing. 

[Callie Beller Diesel]

I’m about to try it with Sue’s Clear:

27 Frit 3124

25 Silica

18 EPK

15 Whiting

15 Neph Sye

Edited to add:

I will report back with pics when they’re finished. I put a little manganese in the iron tea as well, so I don’t know if that will affect how it does/doesn’t dissolve into the glaze. 

Re the alkalinity: I did wonder if the alkaline components in the dish soap would affect the acidity of the tea. I assume, given the results we got, that any sodium elements in our soap were neutralized by the acid, and the surfactants were giving the effect a bit of a boost too.

[PeterH]

Any relevance???

Cardew's Red† aims to suspend Fe2O3 crystals in a glaze body in which Fe2O3 is insoluble.

The recipe is:
44% North Cape nepheline syenite
34% Potash felspar
20% AB clay
2%  Kaolin

... which is attempting to achieve
0.8 K2O
0.2 Na2O
1.17 Al2O3
0.05 Fe2O3
5.35 SiO2
... with a significant emphasis on no Ca and other alkali earths.

The idea seems to be that the Fe2O3 crystals in the clay become suspended in the melting glaze. So it's hard to argue that the F2O3 acts as a flux in this case.

So remove the Fe2O3 from the ingredients and the resultant glaze might not dissolve mocha patterns?

† Pioneer Pottery, Michael Cardew p160

PS It's a cone 8 glaze, perhaps a little boron?

[B.J.]

I finally tried the mocha diffusion and am posting one of my unfired pieces. I'm looking forward to putting it through a  bisque and glaze firing.

[Callie Beller Diesel]

Report back re: Sue’s clear

We found that the brown/black mocha tea that was oxide based did loose a bunch of the fine detail, but the green mason stain version did not. @Min, you mentioned that you thought the green looked like there was too much pigment in that one. Idk if it’s pigment saturation level, or if it’s the weight of the particles themselves. I’ll try another tea with black mason stain and see if there’s a difference. 

[Min]

7 hours ago, Callie Beller Diesel said:

Report back re: Sue’s clear

We found that the brown/black mocha tea that was oxide based did loose a bunch of the fine detail, but the green mason stain version did not. @Min, you mentioned that you thought the green looked like there was too much pigment in that one. Idk if it’s pigment saturation level, or if it’s the weight of the particles themselves. I’ll try another tea with black mason stain and see if there’s a difference. 

@Callie Beller Diesel, when I used green stain it formed the dendrites much more readily than the test pot in your link above. My green tea wasn't very visible in the gray slip I was using it in. I think your stained tea is too heavy to spread out, I would try way less stain. I don't have my old notes handy but just off the top of my head it would have been something like 1/4 - 1/2 tsp stain in about 1/4 cup vinegar. I used to test the reactions on a scrap piece of plexiglass to see how the tea spread then add more vinegar if necessary.