Pir

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

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.

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...

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!

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

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

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?

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

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

Thanks Callie

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

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!

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.

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

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.

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

Interesting! Will have to try... eventually.

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.

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

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...

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...

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

Wait, what's MAGMA?

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!

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