[glaze for mocha diffusion design?]

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

 

[glaze for mocha diffusion design?]

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.

[glaze for mocha diffusion design?]

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...

[glaze for mocha diffusion design?]

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!

[glaze for mocha diffusion design?]

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

[glaze for mocha diffusion design?]

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

... on p21 it states that

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

[Save the Glaze!]

Hi Min,  I fire to cone 6. I guess it is a slip. Aren't there "slip glazes," too? This makes a soft smooth low-gloss, satin-like surface. I'll post pics of it over the weekend.

Besides the amount of clay, are there any differences between a glaze and a slip?

 

[Save the Glaze!]

A while back I bungled this beautiful recipe:

Alberta slip 85 / neph sye 5 /wollastonite 10 (This is called "mouse black;" it has 2% cobalt ox and normally calls for Albany; Alberta is much different/better! In this batch I skipped the cobalt and added 10% RiO, as I discovered this produces a very cool black and dark green dynamic.)

While making a 20x batch, I added an extra 0 to my neph sye 100 figure, so: Alberta slip 1700 / neph sye 1000 /wollastonite 200.

So... I essentially made Alberta slip 58.6 / neph sye 34.4 /wollastonite  7

At cone 6, this botched batch melts and produces a pretty dark, flat brown.

I'm thinking about how to do something to it to make it a decent glaze... maybe a cone 10 shino, for instance (that high neph sye looks sort of like other shinos)? (I haven't tested it at cone 10 as it is.)

Any ideas or suggestions as to how I might proceed?

Thanks, Pir

[determining weight of dry ingredients v. water in a glaze]

1 hour ago, JohnnyK said:

How about you take 100g of the wet glaze and dry it out? You could spread the glaze on a cookie sheet and air dry it first and then maybe put it in an oven at about 150 degrees for a while to dry it out further. Then measure the weight of the dry materials. Then you can easily calculate the weight of the additive...   As I see it, you could have done this in less time than you're spending trying to make the above calculations and the results would be definitive...I think...

Very likely! Will keep that in mind for my next blunder.

[determining weight of dry ingredients v. water in a glaze]

Thanks Callie

[How do I choose a kiln?]

14 hours ago, oldlady said:

pir, there is one other thing that you should consider.   how tall are you and how far down into the kiln you buy can you reach?   can you load shelves and pots easily today?   for 20 or thirty years in the future?

Thank you, Oldlady! The studio manager--mid-20s--of the arts center where I bring my stuff to be fired is recovering from a back injury, which he attributes to loading/unloading.

I've never thought about bricks and how they are damaged--though I've noticed most used kilns seem to have brick gouges and damage.

And I keep hearing positive things about L&L. 

Pir

[determining weight of dry ingredients v. water in a glaze]

1 hour ago, Callie Beller Diesel said:

According to the MSDS sheet, mason stain 6600 has a specific gravity of 5.2.

Ah! Okay. I just took 700 grams of a base glaze and I want to add 5% black stain.

At the 2.6 average SG-dry, the calculator determines there are 389.1 grams dry = add 19.45 grams black.

At 5.2 for Black 6600, we get 296.5 grams dry = add 14.8 grams black.

So... some difference... I'll go with the 14.8 grams.

Where did you find the MSDS sheet?

Thanks!

 

[determining weight of dry ingredients v. water in a glaze]

35 minutes ago, Callie Beller Diesel said:

It might not work well for fixing something with minuscule amounts of a glaze ingredient that has a very strong effect on the glaze, but for most things, it should.  I’m thinking of chrome tin pinks, or something with fractional amounts of cobalt or silicon carbide. 

For me it was black stain. Would that be such material, in your opinion? Since I added less, based on my incomplete calculation, than the amount suggested by old Brongniart, I can always add more if the test comes out gray.

[determining weight of dry ingredients v. water in a glaze]

That damn inter-grain air--I can imagine that factor, as though in a movie, being neglected and then throwing everything wildly off course. 

[determining weight of dry ingredients v. water in a glaze]

By golly, I did it. I mean, manually, pen-and-paper. It worked out same as the calculator. Neat! And I see you're using the second method because I didn't offer the volume of the glaze... and I suppose finding the volume of the dry materials wouldn't be helpful, as dry glaze powders aren't measured by volume (at least not by me).

Tonight I'll do a real-world test and see if it corresponds.

Thanks, Peter.

 

[glaze for mocha diffusion design?]

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

[Low specific gravity but THICK!]

15 minutes ago, Min said:

https://www.brackers.com/wp-content/uploads/2010/11/magmainfo.pdf

https://www.brackers.com/magma-miracle-anti-gravity-multipurpose-additive/

Interesting! Will have to try... eventually.

[determining weight of dry ingredients v. water in a glaze]

5 hours ago, PeterH said:

SG-of-glaze = weight-of-glaze/volume-of-glaze

weight-of-glaze = weight-of-water +  weight-of-glaze-powder

volume-of-glaze = weight-of-water/SG-of water +  weight-of-glaze-powder/SG-of-glaze-powder

Once you can agree with that, the rest is just arithmetic.

This I understand. Although "weight-of-glaze-powder" is the unknown, in my case. Brongniart’s formula, as it's written, with the -1 and the 1-1 etc., still doesn't compute for me, but I'm happy to use the calculator. I wonder if you'd like G. Spencer Brown's book, The Laws of Form, which I always think of when confronted with impossible looking mathematics. I can't get past the first five pages, myself.

[Low specific gravity but THICK!]

On 10/21/2022 at 4:52 PM, Callie Beller Diesel said:

The reason you got cracking after that is more likely because of the clay content. Combined, that’s 20%, which can be a big high. Because you can’t really remove clay without affecting silica or alumina levels, you could either just use 20% epk (shrinks less when it dries than ball clay), or calcine half of the clay before adding it to your recipe.  

On 10/24/2022 at 5:53 PM, Min said:

It's just fine tuning the math, round up or down by the hundredths and you can get the ratios exact. I don't know to which decimal point Glazy will go to. Probably not significant.

Hi Callie and Min, regarding that satin black (John Britt's x10 in his book) that was cracking upon drying (and after firing showed the crack lines or even crawled), I wanted to say I tried both your advice: I recalculated and reduced the ball clay/increased the EPK. Haven't fired yet, but test pieces did NOT crack!

Then I thinned the original, problematic batch, and gelled with Epsom salts: test tiles showed only hairline cracking where thicker. So, we'll see how they fire up.

Thanks again!

Pir

[Low specific gravity but THICK!]

15 hours ago, Min said:

I have a cone 10 glaze with just under 65% nepheline, some dolomite and zircopax plus just under 5% ball clay. It sinks like a stone in no time, however I've gone a year between uses of it and it still stays suspended with some MAGMA. This stuff will float rocks as @Mark C. often says. 

The 5 whiting aka calcium carb will mess with the vinegar. Carbonates + vinegar = CO2 gas, might be enough to negate the effects of the vinegar. Another thing you can try is calcium chloride instead of epsom salts. (it's sold as ice melt)

I'm beginning to wonder if glazes with neph sye are a bit more reluctant to gel with Epsom salts. Thanks for the info on the vinegar and calcium/whiting.

I played with 7 or 8 glazes last night, testing them on test tiles and fingers to watch dripping, thinning them, adding Epsom solution, testing more and watching the finger tests get better and better. Sometimes they got too gelled, so I added a drip of Darvan or water, etc. Watching the glazes spin in the buckets, they went from watery and "endless" spinning, to gelled and coming to a firm stop after 2-3 second--however, that bounce back indicating thixotropy was sometimes elusive, or so subtle as to be hard to detect. Anyway, think I'm getting the hang of it. (Hope my fired results will corroborate this feeling.)

I have a few lovely heavy-Alberta slip glazes (85%) that have always seemed to apply pretty well as they are, although maybe I'll try to thin and gel a few cups just to see. Hansen/Digitalfire and even the Alberta Slip website seem confident that even 40 or 50% Alberta slip will crack on drying (and or crawl, I think), and therefore one needs a "roasted" or calcined portion, but luckily this hasn't been my experience, though I wonder why...

 

[Low specific gravity but THICK!]

14 hours ago, Dick White said:

Flocculants are mildly acidic. Deflocculants, except Darvan, are mildly alkaline.  So... muriatic acid, and common white vinegar are clearly acids, but epsom salts (magnesium sulfate), and calcium chloride (swimming pool calcium hardness increaser) are also acidic, and all the above serve well as flocculants. The dry chems (epsom salts and calcium chloride) must be dissolved in the appropriate amount of water to achieve a saturated solution, but the muriatic and vinegar are already liquid. The muriatic acid is already mixed to a fairly strong solution, so only a few drops are needed and it will create a reaction as it hits the water, hence the fizzing. 

Thanks, Dick. I've never used it. Oh, and the vinegar I used was apple cider... I'm sure it's still acidic, but probably not great if the "mother" gets into the glaze...

[Low specific gravity but THICK!]

14 hours ago, Kelly in AK said:

Something I just remembered seeing years ago was Tom Coleman in a workshop using muriatic acid to suspend glazes. I can’t remember the reason, but he preferred it to Epsom salts. Fizzed up when he put it in. Not something I’d try casually, but maybe worth researching. 

I've never heard of it, but I see it's Hydrochloric Acid (HCl).

[Low specific gravity but THICK!]

15 hours ago, Min said:

it still stays suspended with some MAGMA.

Wait, what's MAGMA?

[determining weight of dry ingredients v. water in a glaze]

Wow, huh, hmm, man, that was complex! Thanks for showing me that.

Have you used this calculator and gotten correct results, I mean, you actually applied it to an amount of some addition you wanted in a glaze and it came out properly? 

I suppose there must also be a way to test it with a simple 100 gram dry recipe + a known weight of water (before adding). As I said, I'm not mathematically inclined, so this reverse engineering might be terribly obvious, or maybe you've shown that already... I'll have to actually go thru the steps, though!

[Low specific gravity but THICK!]

So, I tried to rescue a bad glaze via the Hansen/Digitalfire method we've been discussing on this thread. I've used epsom salts before, successfully (i.e., it noticeably and quickly gels), but last night I tried it in a simple white mat recipe (which applies just awfully)--

neph sye 35 / dolomite 20 / whiting 5 / EPK 20 / silica 20

--but the epsom salts did NOTHING! I brought the glaze down to 1.44 or 1.45. I used a concentrated solution; I made another batch to be sure it was super concentrated; I added a liquid bentonite (my suspicion was that more clay might be needed?); and then I even added vinegar (last ditch effort), and nothing got that damn glaze any better:  it remained thin on the finger; it dripped all over the test tiles; it kept spinning in the bucket; it never bounced back, reflecting thixotropy. And, slow dry.

The glaze has been sitting for 5  or 6 months, I'd guess; and I did dump off the yellowish water from the top (soluble stuff from the neph sye?) and added new. (Hansen's got me wondering about my tap water now!) It also may be the case that some months back I tried adding Ep salt, too.  

Anyway, if those factors don't apply, I wonder what's preventing this glaze from playing nicely? 

Pir