Mocha Diffusion

[Dave K]

I have been experimenting with mocha diffusion and I am to a point where it almost works. My problem is the slip sets up too quick to add much color. I am using a slip recipe by Robin Hopper and I added about 1% soda ash as a deflocculate. Any ideas on how I can extend the drying time on the slip?

[oldlady]

since it is his recipe, why not ask robin hopper?  or, maybe it is in his books, you are surely not the first person with this problem.   try our own doc weathers, he has investigated this very well.

[Foxden]

Are you applying the slip to leather hard ware? If so, let it be a bit less dry, that should help.

[curt]

bentonite?

[PeterH]

That was my problem too, the few times I tried.

 

Just looked up a few utube videos on mocha diffusion, it's a surprise just how fast they seem to work

(assuming that the videos are uncut and in real-time).

 

Less than 30secs from bucket to completion on this one

 

 

Usability seems to stop after 10secs on this one

 

 

 

I'm truly uncertain how deflocculating the slip will effect things "chemically", but given the mildly acidic

nature of most mocha teas I suspect that soda ash will. Also deflocculation means that you have more

"clay" for a given viscosity, which might effect the drying time of the slip.

 

One of Robin's slips is given in:

http://rhrising.blogspot.co.uk/2013/03/mocha-diffusions.html

SUITABLE SLIPS
Various slip recipes are good, the most important ingredient being a high
percentage of ball clay.  A basic recipe which will fit most bodies and
which can easily be colored with stains or various oxides would be;  
BALL CLAY 75, KAOLIN 10, SILICA 10, FELDSPAR 5.
I have taught this process all over the world and you can use any ball clay,
any feldspar, any kaolin and any 200 mesh silica, flint or quartz.  They will
all work. This slip is good on most clay bodies from cone 04 to 12,  in any
atmosphere. The thickness should be like double cream, or room temperature
10 W 30 motor oil. A liquified porcelain clay slip will not usually work well
since a porcelain body usually contains a maximum of 50% plastic clay material,
the remainder being non-plastic fluxes and fillers such as feldspars and silica.
 

PeterH

 

PS if only for for the humour:

http://www.potters.org/subject05546.htm

Peter Linford on thu 22 jul 99
Hi Martin,
I too used to mix up disgusting fluids till one day washing brushes
discovered that a mix of oxide and washing up liquid works just as well and
the brushes are really easy to clean.
hope this will help
Peter in Wakefield, Yorkshire.
 

 

[Dave K]

Thanks so much for all of the replys. The utube videos were helpful. How would I contact Doc Weathers?

[High Bridge Pottery]

In the video the potter mentioned the tea was alkaline. Deflocculation will neutralise the acidic slip.

 

I would try adding vinegar instead and getting it to gel + more acid and doesn't bentonite hold water well. Maybe test some %'s of that.

 

Isn't @docweathers a member.

[Dave K]

Do you mean add vinegar to the slip? The above utube led me to another video when it was done with a woman applying various color acid mixtures to a pot. The video was 8 minutes long and her slip stayed wet the entire time.

 

I started this post while I was doing a bisque fire that included the mocha pieces. When they came out they were " dusty" and easy to smear the color. I wiped one with a damp sponge and it took half or more of the color off. Is any of this normal? I used cider vinegar with mason stain for my acid solution.

[oldlady]

you appear to be trying too hard.  could you just try using a greenware piece that you just finished making, put slip on it, touch a brush with your vinegar and color solution to a tiny spot and watch the tree grow.  put that pot down and make another one.  it is really that simple.

[High Bridge Pottery]

It does seem to be the other way round than he said in the video. Acid colour solution and alkaline slip.

[docweathers]

To keep my mocha slip damp while the diffusion is going on I have put a steamer that vents into my spray booth. It radically raises the humidity in that small area. The slip dries very slowly or if you're not careful not all. You don't want the blast of steam aimed at your pot.