Pir

Hi Kelly, I'm obsessed with SG, but I never sieve twice! I'm hoping that sieving twice isn't that important--but please correct me if I'm wrong. I'm just getting around to attempting to substitute Gerstley Borate with a frit, but I'm finding I will need to some extra Glazy experience/training (I've done simple substitutions, like MgO for talc, but I was stumped when trying to sub a frit). I was comparing two floating blue recipes, one with GB, and a Britt version with a frit, and his recipe reflected perfectly what Hansen writes about regarding the benefits of such a sub: the frit drastically lowers the GB (the frit supplies boron, but doesn't gel the glaze like GB); he adds more EPK to suspend and to supply Al (frit had no Al); he uses less neph sye (frit had sodium). I've used epsom salts before, successfully, 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 efforts), and nothing got that damn glaze any better--i.e., 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. I'm going to post this on my other thread to see if anyone has any ideas... Low specific gravity but THICK! Pir

Thanks, Peter... Wow, that's even more confusing (for me). I didn't expect that the mass or the specific gravity of dry materials came into play. The other day I wanted to add 5% black stain to a high-calcium semi-mat clear--it makes a deep, glossy black (somehow). Here's a comparison. The method I used was: SG of glaze 142... 100/142 = .70 2640 grams in the bucket x .70 = 1859 grams wet subtracted from total = 780 grams dry x .05 grams of stain = 39 grams of black stain to be added. But when I plugged those #s into the Brongniart calculator I get 1268.9 grams of dry, which multiplied by .05 = 63.4 grams of black stain to be added. I guess I'll see how the test tiles turn out!

Thanks again to Hulk, Min, Callie and others for answering questions I had in 2021... which are similar to the ones I've posted (and you've answered) this year! It's taken so long for some of these concepts to sink in. Pir

I just got a TaoTronics TT-AP007 air purifier, two of them actually, unopened at a garage sale for $40 a piece. Can't beat that price. This one shows a PM value. When I turned it on, the PM was in the 30s; when I began mixing up dry materials for a glaze, the fan cranked up and the value rocketed into the 800s! So, it seems to detect the dust!

Is this the correct mathematical procedure? I got it from this (rather confusing) thread: http://www.potters.org/subject72185.htm and it seems to work. I want to add, say, 3% of an oxide to a glaze that's already made. In order to know how many grams to add, I need to do this: 1. 100/Specific Gravity 100/145 = 0.6896 (or 69% water) 2. Weight of glaze batch, say, 350 grams X % water 350 X 0.6896 = 241 grams of water 3. Weight of glaze batch - weight of water 350-241 = 109 grams dry materials 4. Dry weight X % oxide to be supplied 109 grams X 0.03 = 3.27 grams of oxide. I was confused about step 1 when I saw this on Digitalfire: "This deflocculated slurry of 1.79 specific gravity (only 28% water)." By my calculations, 100/179 = 0.5586, or 56% water, not 28%. Am I getting something wrong here? I am not mathematically inclined... Thanks, Pir

I did notice that he emphasized "stirring vigorously" when he mentioned adding powdered epsom salts! Maybe it's simply to avoid additional liquid.

Thanks Callie, I had to sleep on this, and this morning I've been pouring over Digitalfire articles (again)! Anyway, yes, I will floc that 4321 with some epsom salt solution. Interesting with Hansen describing how he gets a lower SG (1.43-1.45) and then flocculates. He uses epsom salt powder, which I haven't seen yet; I also haven't tried vinegar yet. P

Thanks, Callie, but I'm also really trying to understand if the remixing (without additions) changes that "deck of cards" structure Pinnell mentions, i.e., from a dense deck (not good for absorption) to a porous house (good for absorption). In other words, if it looks mixed and suspended after having settled and been remixed, are the clay particles open, thus allowing quick drying? Or, can it look mixed and suspended with the clay particles still being densely layered, thus not drying quickly? I'm guessing/hoping that the mixing does change the clay particle structure for better absorption. I just wonder, if we go back to Pinnell's metaphor about dipping into a deflocculated glaze and getting the deck of cards structure, how one would even dip into such a settled glaze. What I don't want is to dip into a glaze that look good, but still get the dense deck of cards.

Here's another floc/defloc question, if anyone's still checking in (thanks again for all the generous advice!!): From Pinnell's article, https://www.claytimes.com/articles/glazeadjusting.html "In addition, when clay is in a deflocculated state, it settles into a structure not unlike a deck of cards: parallel to each other and tightly packed together...a deflocculated glaze also acts differently when you apply it. When a pot is dipped into the glaze, the clay particles in the glaze will align into parallel layers on the surface, sealing off the pores of the bisque ware. .... A deflocculated glaze will stay wet on the surface, allowing the glaze to form a maddening number of drips and forcing the potter to stand forever waiting to put the pot down. At its worst, a deflocculated glaze will only go on in a thin layer and, when dry, will have a crystalline, drippy look... When clay and water are in a flocculated state the clay has a structure like a house of cards: very open and porous. The result is that the glaze can build up quickly on the surface of the pot because there is nothing to impede the flow of water into the pores of the bisque. This becomes obvious when the pot is withdrawn from the bucket of glaze: the glaze coat will seem to dry almost instantly, with little or no dripping." So, I just saw that my Leach Clear had settled and needed a bit of spatula work to unsettle (I mixed it up, too, and put it through an 80 mesh again). So, it was in a deflocculated state--the clay particles like "a deck of cards" atop one another. Now that I mixed it up, is it back in a floculated state, "a house of cards"? Was the remixing enough to alter the attraction and structure of the clay particles? Or is some other step needed? Thanks All. Pir

I'm definitely not that handy!

Thanks once again, Neil. Lots of work ahead of me! Pir

Can I also ask: how important is ventilation for a kiln? I'm assuming VERY. I've come across some studio options that look good except they have no easy way to vent. At worst, I'd guess one would simply have to be out of the room while the kiln is cooking... Or is it worse than that? i.e., lingering fumes, fumes drifting into other parts of a building, etc. Pir

Hi Niel, Thanks again. This encourages me to hold out until I can get something close to the best option for me, rather than settle for something older, less user-friendly, more costly, etc. Best, Pir

Thanks, Denice, Yes, I find that we are our own harshest critics of our work, and I attribute that to expectation: when our expectations about a glaze--how it should turn out--fall short, there is dissatisfaction...but often, for me, as time passes and the memory of what I expected grows dim, I can see the piece/glaze differently, and actually come to appreciate it. Pir

Thanks very much, Neil. Given the greater power and efficiency of three phase vs single phase (according to what I'm reading), and assuming the building is set up for it, should one aim for a three phase? Thanks again, Pir

Hi, I am stumped on how to buy a kiln. Be warned, I am very green when it comes to kilns, as these questions will betray! My first question is this: when I see a kiln as advertised as Max Temp: 1800, what cone does this reach? Is it the case that 1800 degrees + time can reach a higher temperature/cone, or does max temp translate directly to a particular cone? (This relates to a small programmable glass-fusing kiln I see on Marketplace for $450, a Skutt GM-814--the price and size are attractive, but does this reach cone 6?) Next: How does one determine if they need a single or 3-phase kiln if they don't know where the kiln will eventually go?! My studio circumstances are likely to change soon (new owners bought the building, making "improvements," raising rent, etc.). I understand a 3-phase can work in a building with a single or 3-phase setup, but a single-phase will not work in a building with only a 3-phase, I think, right? More generally, having never much used an older kiln sitter, and having some experience with a fancy programmable Skutt, I am naturally leaning toward the latter. I'd be interested in various ramps/holds, slow cools, etc., and I just don't know how (or if) that is done on the older types. Then again, I am not a production potter (not yet anyway, and I don't know if I want to be one), so I am an amateur, and I can probably live with a simpler, cheaper kiln to start. This makes me wonder about size, too--smaller size might be better, as I like making and testing glazes (at least for now). And then there's brand: Someone suggested L&Ls are best (and that replacing elements is easy on these)--might an older L&L be as good as a newer programmable Skutt?--and another person said they wouldn't buy a Paragon. I'm always seeing kilns on Facebook Marketplace (for Rochester, NY), but "it's all Greek to me." Advice is warmly welcomed. Pir

Hi Callie, thanks for the frit info. I'll try my egg beater on the next attempt to add Darvan. And I do have a drill and mixer, so I'll be sure to use that. P

Hi Callie, I haven't tried substituting with frits, yet. I assume I'd look at the various dominating ingredients in various frits and pick one matching the material I'm subbing it with, and then just tinker with the software. Britt's book calls for bentonite in nearly every recipe, I think. I've only mixed in Darvan in small batches, like 500ml. And I whisk the heck out of it. I could see how a couple of swirls with a paddle in a 5-gallon bucket might not do it, but I'd be surprised if I was getting the Darvan mixed in well enough in these small batches... But then, I've been surprised before.

Thanks, Philo110. Have you noticed a change in the air quality? Pir

Yes, scale good, and I'm careful with measuring. That gerstley again! I've got a few frits I can look into... 10 clay... I thought adding bentonite would be superfluous because of the ger bor and EPK... i.e. other things keeping things in suspension...?

Here's another thick glaze I needed to recalculate for lack of talc. I mixed a 2x sample, let it sit in water overnight, next morning it was peanut butter. Could ball it up with fingers. I added just enough water to get it to flow into a beaker to measure specific gravity--the SG is 120! Britt's rec for the glaze is 160 (book)! Darvan doesn't do much. More? Next day I add to the glaze another 2x, dry, and that gets me to 150, still very thick or viscous. Darvan still doesn't do much. I finally added water, 138 SG, applied much better. So... 138 fluid glaze vs 150 gelled glaze...? We'll see how the test pieces compare ...in some weeks... I don't have my own kiln yet : ( .

Thanks, Min. LOi is something I've largely ignored, being so occupied with learning so many other glaze things! Just to be clear, the John 10X original I got from the Mid-Fire book, and it has only 10 Si. I wasn't sure if you were saying there was another version with 20? Anyway, I'd be interested to see what a slightly glossier satin would look like. Perhaps like a piece of water polished black jade (one can dream!). Pir

Hi Min, I'm not sure why I used Custer--probably I was out of G200 (now I do have F4, or minspar, which I think is a sub). I use 325 mesh silica--because that's what I bought, not because I have experience using other meshes. Mesh along with calcining materials are, thus far, outside of my experience range! What were you looking to do with the recipe? This version of satin black works okay, except on some clays it leaves the impression of crack lines (which I'm understanding from previous comments as a manifestation of the clay drying--someone suggested using all EPK, as it's quicker to dry than ball). I haven't really tested it with cutlery or acid to see about leaching--these are also things I haven't quite built into my glaze testing habits yet. In other words, aside from the viscosity (at 153 SG), it seems like a well-behaved glaze (after a little Darvan and a splash of water). But perhaps the G200 would alter things; or the extra silica, as you're suggesting. Did you have any idea about why the Glazy quantities looked the same but the ratios looked different? Is Insight better software? Is it open to use?

Min, I use Glazy--is Insight different? I see on Glazy that while the two formulas show identical quantities of oxides, the ratios are off. That's always confused me.