glaze for mocha diffusion design?

[Pir]

Hello, I just tried mocha diffusion for the first time, and it was so fun that I made way too many pieces. The bisque-fired pieces came out nicely. I glazed two cups and fired to cone 6:

1. One cup was Laguna speckled buff clay with a volcanic ash clear (transparent, glossy)--the result was patchy, muddy (as though the slip itself had moved around on the surface), with the diffusion designs severely muted and difficult to see.

2. Cup two was Laguana 55, a nice off-white clay body with just a little tooth to it, glazed with a high calcium clear (translucent)--a much cleaner result, but again the sharp dendritic detail of the diffusion design was muted or blurred.

I used two acid "inks"--manganese (which turned brown, sadly--has anyone used black stain?) and red iron oxide.

I just read in a glaze book that a fritted glaze is "less likely to attack an underglaze colorant design." I'm keen to find a high-frit clear and test that (assuming "attack" could mean blur, etc).

Does anyone have and advice for preserving a sharp diffusion design?

Thanks, Pir

[Min]

You want the glaze to be as stiff as possible to not diffuse / blur / run the colourants used. Just like with underglazes if the glaze is a fluid one it will cause running / blurring of the colourants. I have used a green stain, it worked as did a mix of cobalt and manganese dioxide. If you use cobalt carb it is very hard to see until bisque fired and easy to smudge. Cobalt ox is easier to see but since the particles are heavier it can be result in a less dramatic patterning but still good.

I used mocha diffusion a bit differently than it's typically used, used red iron oxide in the slip then the tea with cobalt + manganese then used an opacified white satin glaze overtop. The opacified glaze definitely blurred the dendritic patterning of the diffusion but that was what I was going for. At the time I did it there were a lot of people making the typical trees and shrubs, I went with raindrops. This is the only piece I still have a picture of with the opacified glaze overtop. For the green stain I used a clear and the patterning showed better.

 

[Brie]

https://www.lagunaclay.com/product-page/wc401-b-mix-5
 

we did this in my studio and the pieces came out pretty nice with this clay and the recycled clay 

[Pir]

Thanks, Min, a stiff glaze makes sense. Now, to find one.

I love the raindrops. They say nature never makes an aesthetic mistake--no such thing as an ugly cloud. Incorporating natural patterns onto pottery surfaces, already itself very "natural," is exciting. Hope I can get it to work.

[Pir]

Thanks, Brie... Do you recall the glaze you used?

[Ben xyz]

On 10/15/2022 at 8:36 AM, Min said:

You want the glaze to be as stiff as possible to not diffuse / blur / run the colourants used. Just like with underglazes if the glaze is a fluid one it will cause running / blurring of the colourants. I have used a green stain, it worked as did a mix of cobalt and manganese dioxide. If you use cobalt carb it is very hard to see until bisque fired and easy to smudge. Cobalt ox is easier to see but since the particles are heavier it can be result in a less dramatic patterning but still good.

I used mocha diffusion a bit differently than it's typically used, used red iron oxide in the slip then the tea with cobalt + manganese then used an opacified white satin glaze overtop. The opacified glaze definitely blurred the dendritic patterning of the diffusion but that was what I was going for. At the time I did it there were a lot of people making the typical trees and shrubs, I went with raindrops. This is the only piece I still have a picture of with the opacified glaze overtop. For the green stain I used a clear and the patterning showed better.

 

Thanks Min - looks beautiful! I’m happy enough with the magnesium dioxide + cobalt oxide (plus a few drops of liquid soap) on top of Hopper’s slip recipe; b-mix cone 6 clay body.
A. Now unsure about using a clear zinc-free glaze on top that could possibly soften the dendritic patterning, though would like to correct hairline crack I found.

My preference is to lessen the contrast somewhat between dark markings and white slip background.

B. I’m considering firing at cone 10 (to darken the whiteness of the slip?), but again concerned about the fragility of the patterning (and the crack).
C. Another option would be to lightly spray an oxide onto the bisque, forget the clear, and fire at 6 (still want transparency to reveal the patterning).

Suggestions? Thanks.

[Min]

6 hours ago, Ben xyz said:

though would like to correct hairline crack I found

You lost me here, the slip has a crack or the pot?

A - I don't know how your glaze would look on the patterning, would have to try a test piece and see. 

B - Is it a cone 10 clay or would this be a different piece of work? You can colour the slip with stains or a darker firing ball clay if you have one for the next one you make.

C - Using no glaze gives the clearest patterning, this is what Hopper did on the outside of his vessels but be careful if you glaze the inside as you need a really well fitting glaze if you only glaze one side of a pot to avoid dunting / cracking of the pot due to uneven tensions. 

Suggestions - make some tests. If you find the contrast of the dark cobalt + manganese and the slip is to harsh try using just a very small bit of colourants, it will still be blue but might not be as dark. Cobalt is very strong, doesn't take much to get blue.

BTW, typo in your oxides, manganese dioxide not magnesium. 

[Ben xyz]

 

4 hours ago, Min said:

You lost me here, the slip has a crack or the pot?

A - I don't know how your glaze would look on the patterning, would have to try a test piece and see. 

B - Is it a cone 10 clay or would this be a different piece of work? You can colour the slip with stains or a darker firing ball clay if you have one for the next one you make.

C - Using no glaze gives the clearest patterning, this is what Hopper did on the outside of his vessels but be careful if you glaze the inside as you need a really well fitting glaze if you only glaze one side of a pot to avoid dunting / cracking of the pot due to uneven tensions. 

Suggestions - make some tests. If you find the contrast of the dark cobalt + manganese and the slip is to harsh try using just a very small bit of colourants, it will still be blue but might not be as dark. Cobalt is very strong, doesn't take much to get blue.

BTW, typo in your oxides, manganese dioxide not magnesium. 

Sorry about that - the plate (pot) has a hairline crack. Although it would be a zinc-free clear glaze (c6), I don’t want the possibility of sacrificing the diffusion effect. Will do some tests.
 

Will likely try your colourants suggestion and lightly spray on a small amount of watered-down stain and/or oxide over the bisque surface and forget about the clear glaze for now, then fire at 6. The  clay (B-mix c6) can be fired at 10, but this might stress out the slip and coloringe agents used. Appreciate the spelling correction. Have a bad habit of doing that - not great for mixing glazes! Thanks Min for your help.

[Kelly in AK]

I don’t think you can fire Laguna B-mix 5 to cone 10. There is a B-mix 10 that is cone 10 clay. They look the same but they’re not the same formula. 

[Pir]

9 hours ago, Min said:

C - Using no glaze gives the clearest patterning, this is what Hopper did on the outside of his vessels but be careful if you glaze the inside as you need a really well fitting glaze if you only glaze one side of a pot to avoid dunting / cracking of the pot due to uneven tensions. 

I'm still searching for a glaze that will preserve, to a larger extent, the crispness of the designs and the sharpness of color of mocha-diffusion designs.

Easy E Clear--with some 20% frit--seemed slightly better on speckle buff clay (cone 6) than on a white body clay, in terms of that preservation.

Small revelation last night: I glazed the inside of a mo-diffusion cup first, and as it dried a yellow stain crept out onto the outer walls. This explained why my previous tests came out yellowish post-fire where the slip should've been white. (I sponged it away, will see if it appears post-fire.) I feel like I just read this somewhere: glaze the outsides first... or at least if it's a fritted glaze? ...to avoid exactly this. ( this is frit 3124; also some neph sye in there, but not sure if that creeps out yellow.)

I tend to glaze all my pieces inside first, then outside (when I don't have a large enough batch to fully dip). I'm sure there are differing views on this...like everything!

Pir

[PeterH]

On 10/15/2022 at 2:19 PM, Pir said:

I used two acid "inks"--manganese (which turned brown, sadly--has anyone used black stain?) and red iron oxide.

Robin Hopper confirms that the use of stains is OK in
Mocha Diffusion
https://ceramicartsnetwork.org/pottery-making-illustrated/pottery-making-illustrated-article/Mocha-Diffusion#

A comparison of different "pigments" "acids" is given in
An Exploration of the Variables Involved inCreating Mocha Diffusions
https://francesgwilliamceramics.files.wordpress.com/2019/06/an-exploration-of-the-variables-involved-in-creating-mocha-diffusions-frances-gwilliam-st20086157.pdf
... on p21 it states that
At stoneware temperature there is colour loss in the tendrils. The main body has the same
metallic brown as it has at the unglazed earthenware stage, but is slightly shinier. When glazed
the colour is almost completely absorbed. Even on the main body the colour vibrancy
decreases significantly. The tendrils become very faint lines.
Manganese Oxide works well initially as colourant for mocha diffusion, but I wouldn’t suggest
using it above earthenware temperature with glaze. The colour stays mostly consistent
through firing temperatures but is absorbed too much by the glaze at higher temperatures.

PS Stumbled across these, which might be of interest

A rather "different" style of feathering
See https://www.youtube.com/watch?v=cSrWRWILaZo

Thought provoking eye-candy
Satisfying Mocha Diffusion Compilation
https://www.youtube.com/watch?v=WjocYCaPsUM

And a classroom science paper in  Japanese (Google translate doesn't seem to work).
Fractal growth method applicable in class: Fractal dimension and growth characteristics of Mocha diffusion patterns with surfactant
https://tinyurl.com/mr3hfj6v
The pattern when the dye solution containing polysorbate80, a surfactant, was dropped on a 1: 1 mass ratio of kaolin and water was analyzed.

so it's definitely not a pottery experiment, but it does raise some interesting questions
- would surfactants work instead of the usual "acids" (e.g. washing up liquid or dishwasher rinse aid)
- as altering the concentration of the surfactant influences the "openness" of the pattern, would watering-down the concentration of the acid have a similar effect? Maybe 50:50?

 

 

Edited November 19, 2022 by PeterH
typo

[Min]

A buddy of my husband burns dendritic patterns into wood. This is some of his work.

[Marilyn T]

 

I am also experimenting with mocha diffusion so here is what I've learned so far about getting crisp(ish) designs on white clay.   I use a black cobalt free Mason Stain # 6650 and a commercial clear Amaco HF zinc free clear.  I experimented with different commercial clear glazes and recipes such as the one from the book Mastering Cone 6 Glazes but none had a clarity of the Amaco.  I also tried mixing the tea with different oxides but the Black Stain mentioned above gave the clearest design.  If you are using Robin Hopper's slip recipe I found after firing it had a yellow tone, so to match it for the rest of the ware I reduce the rutile to  2%  in the bone recipe from MC6 glazes.  I also use Licorice from MC6 glazes as an accent glaze on the outside.  I have yet to try other stains but I did take the course from Kevin Kowalski in which he recommended different color stains.  He uses an Aardvark clear on his work.  

Edited November 19, 2022 by Marilyn T

[Pir]

On 11/19/2022 at 9:05 AM, PeterH said:

... on p21 it states that

Wow, lots to get into! Thanks for the finds.

[Pir]

22 hours ago, Min said:

buddy of my husband burns dendritic patterns into wood. This is some of his work.

Wow, Min, does he free-hand these designs? I wish I could see how detailed the tendrils get. really beautiful

[Pir]

17 hours ago, Marilyn T said:

I am also experimenting with mocha diffusion so here is what I've learned so far about getting crisp(ish) designs on white clay.   I use a black cobalt free Mason Stain # 6650 and a commercial clear Amaco HF zinc free clear.  I experimented with different commercial clear glazes and recipes such as the one from the book Mastering Cone 6 Glazes but none had a clarity of the Amaco.  I also tried mixing the tea with different oxides but the Black Stain mentioned above gave the clearest design.  If you are using Robin Hopper's slip recipe I found after firing it had a yellow tone, so to match it for the rest of the ware I reduce the rutile to  2%  in the bone recipe from MC6 glazes.  I also use Licorice from MC6 glazes as an accent glaze on the outside.  I have yet to try other stains but I did take the course from Kevin Kowalski in which he recommended different color stains.  He uses an Aardvark clear on his work.  

Hi Marilyn,

Did you see in my post about the yellowing with a fritted clear glaze? I'm not sure if it's the culprit of the yellowing.

          Small revelation last night: I glazed the inside of a mo-diffusion cup first, and as it dried a yellow stain crept out onto the outer walls. This explained why my previous tests came out yellowish post-fire where the slip should've been white. (I sponged it away, will see if it appears post-fire.) I feel like I just read this somewhere: glaze the outsides first... or at least if it's a fritted glaze? ...to avoid exactly this. ( this is frit 3124; also some neph sye in there, but not sure if that creeps out yellow.)

I've also used that high ball clay slip that Hopper offers. But I also used another recipe, so I'll have to go back and see if I can determine which was which--and which might've caused the yellowing, if it wasn't the fritted glaze. 

I didn't follow your bit about a bone /rutile recipe in the MC6 glazes... Didn't you settle on the Amaco, or was there another decent clear?

Thanks!

[PeterH]

BTW I quite like this colour combination, and the visual interaction with slightly blotchy background.

... its a manganese dendrite, typically formed by manganese rich water seeping into a crack in a limestone bed.

[Min]

1 hour ago, Pir said:

Min, does he free-hand these designs?

Nope, it's a dangerous method involving salt water and electricity.

1 hour ago, Pir said:

Small revelation last night: I glazed the inside of a mo-diffusion cup first, and as it dried a yellow stain crept out onto the outer walls.

Just mineral salts, seeping through the walls from either a glaze material or just the water itself. I always liner glaze my mugs the day before glazing the outside, happens every time. Hopper's slip is mostly ball clay, fired colour of the ball clay you are using will be the main influence of the slip colour. If you want a whiter slip try finding a ball clay with lower iron. I haven't tried adding zircopax to the slip but could try that too.

[Marilyn T]

Hi Pir,

Re your question:  I didn't follow your bit about a bone /rutile recipe in the MC6 glazes... Didn't you settle on the Amaco, or was there another decent clear?  

I only use a clear glaze over the mocha diffusion part of the decorating.  The rest of the ware is glazed with other glazes, such as MC6 glazes bone and licorice.  In order to match the yellowing slip (with OM#4 ball clay) I reduced the recipe for Bone from MC6 glazes to 2%.  That way there is more of a seamless transition between the mocha diffusion slip colour and the rest of the ware.  For the clear over the mocha diffusion part, I use Amaco.  I also had good visual results with the Clayshare Clear recipe but it didn't pass the functional analysis criteria when run through Insight software so I don't use it.  To glaze, I use latex to cover the parts I don't want the clear glaze sprayed on; then I spray the clear glaze on the mocha diffusion part;  and then once dry, I remove the latex and glaze the inside of the ware and the rest of the outside with a MC6 glaze using a combination of dipping and brushing.  I don't mind the yellowing of the slip as it only shows if I clear glaze the whole piece.  Hope this clarifies it somewhat.  

[Ben xyz]

On 11/19/2022 at 2:13 PM, Marilyn T said:

 

I am also experimenting with mocha diffusion so here is what I've learned so far about getting crisp(ish) designs on white clay.   I use a black cobalt free Mason Stain # 6650 and a commercial clear Amaco HF zinc free clear.  I experimented with different commercial clear glazes and recipes such as the one from the book Mastering Cone 6 Glazes but none had a clarity of the Amaco.  I also tried mixing the tea with different oxides but the Black Stain mentioned above gave the clearest design.  If you are using Robin Hopper's slip recipe I found after firing it had a yellow tone, so to match it for the rest of the ware I reduce the rutile to  2%  in the bone recipe from MC6 glazes.  I also use Licorice from MC6 glazes as an accent glaze on the outside.  I have yet to try other stains but I did take the course from Kevin Kowalski in which he recommended different color stains.  He uses an Aardvark clear on his work.  

So much useful info from a lot of experienced potters! Will likely go with the Cobalt-free Mason Stain 6650 and Amaco’s HF (zinc free) Clear. Since my diffusion was done on greenware, I don’t expect much in the way of smearing (though may spray it on for an even application). Just working on plates for now, so the possible yellowing of the slip formula should be okay. Good to know about the workarounds though for the future.

Used apple cider vinegar and a couple drops of liquid soap with modest success. Beer did not work for me, nor bleach. May try adding nail polish remover to the mix to check that out. Probably need to play around with the thickness of Hopper’s slip as well. Have been tempted to take Kevin Kowalski’s archived workshop - did you find it helpful, Marilyn? Nice diffusion, btw. 

[Pir]

On 11/20/2022 at 2:13 PM, Marilyn T said:

To glaze, I use latex to cover the parts I don't want the clear glaze sprayed on; then I spray the clear glaze on the mocha diffusion part;  and then once dry, I remove the latex and glaze the inside of the ware and the rest of the outside with a MC6 glaze using a combination of dipping and brushing.

I'll have to try that.

I just used a fritted clear (Easy E Clear, I think it's called)--a very quick dip in a very thin slurry preserved the design noticeably better than, say, even that same glaze with some epsom salt. Only problem is that the piece is gritty to the touch...

[Pir]

On 11/22/2022 at 7:29 PM, Ben xyz said:

Since my diffusion was done on greenware, I don’t expect much in the way of smearing

Used apple cider vinegar and a couple drops of liquid soap with modest success. Beer did not work for me, nor bleach.

Hi Ben, have you seen mocha diffusion done on bisqueware? I haven't heard of that. Maybe with an engobe?

For acids, the best by far of those I tried was a tin of tobacco boiled down in a cup or two of water.

[Ben xyz]

15 minutes ago, Pir said:

Hi Ben, have you seen mocha diffusion done on bisqueware? I haven't heard of that. Maybe with an engobe?

For acids, the best by far of those I tried was a tin of tobacco boiled down in a cup or two of water.

Hi Pir,
Nope - was just trying to say that I don’t expect smearing/smudging after bisque firing the diffusion design (c04). Interesting about the tin of tobacco and  boiling it down for the acid, which sounds like the original/traditional  process. Were you able to store it at all, or did it get fairly rank after a couple of  days?

[Pir]

On 11/23/2022 at 9:12 PM, Ben xyz said:

Interesting about the tin of tobacco and  boiling it down for the acid, which sounds like the original/traditional  process. Were you able to store it at all, or did it get fairly rank after a couple of  days?

Well, the smell was bad, but not awful. Stinky, but not unbearably putrid.  Rank, but not rotten. A faint smell of dirty ashtray, behind a deeper sort of swampy musk.

I haven't tried it again, though. I've got a dozen more mocha-diffusion cups and I haven't found a way to preserve the fineness of the dendrites. Some suggestions above to try when I try again. 

Here is the post I read for the "tea."  I haven't tried defloccing the slip. 

 

Andrew S Lubow on thu 12 dec 96

Here is a formula for for a Mocha Tea Stain. Mochaware is classicly
earthenware and stoneware mugs or jugs but I've applied it to tile as
well. To do this you have to freshly apply slip to leatherhard clay by
either dipping or brushing. (Dipping will give a more even surface).
While the slip is still wet touch a loaded brush to the slip. A bullseye
will form from which mosslike or treebranch patterns eminate from. The
patterns stay defined when fired.

Mocha Tea Stain

25 grams of finely chopped tobacco
one pint of water

Boil the mixture for 40 minutes and seive with a 200 mesh
seive. Add either 30 grams iron or manganese oxide then reseive.
The tea can be made in advance and refridgerated but has to be
reseived before each use. This mixture is poisonous keep it safely
away from children and consumables.

Mocha Tea Slip

3 parts Ball Clay
1 part China Clay

If you use your own slip add a defloculant. It may help the reaction.

http://www.potters.org/subject05544.htm