Pyewackette

@oldlady To what cone did you typically fire this?

You don't need to test the oxides. You need to test the GLAZES, each and every one. Wondering why I can't hold my own opinion on this matter, I'm not telling anyone else what to do or not to do. As far as I'm concerned it is way easier to stick with a few glazes you know are durable and safe. A clear, white, or brown (liner) glaze can easily be found that fits my criteria. Still every once in awhile I'd like to be able to add a splash of color to my liner glaze and still be confident it fits MY criteria. Nobody else has to do as I do. However I would appreciate any help offered in identifying the stains that fit MY criteria. Which mostly just means identifying the oxides I want to avoid in a liner glaze. EDIT: @Min Thanks for the testing link. Bookmarked. I may want it someday.

I fully well realize that others think differently on this issue. However I choose to err on the side of caution. Hesselberg & Ron and Tony Hansen of Digital Fire both raise the issue of not knowing for sure whether or not your glazes are TRULY durable/"safe" without proper lab testing, lemon tests and dishwasher rides notwithstanding. I choose to avoid the more toxic colorants in liner glazes, period paragraph. I would just like to know which ones those are. Thanks.

@Dick White All well and good but there are an awful lot of variables involved in determining whether or not a glaze is stable that won't necessarily show up without lab testing. Since I can't afford said testing to start with (and given there are many ways for a formerly stable glaze to destabilize, such as material changes, firing variations, and mistakes in mixing it up) I have decided to stick with the safest possible formulations for my liner glazes. Plus there's the whole expense issue, as you mention. I'm not particularly concerned about exteriors (its not like I'd use anything leaded) but my liner glazes are another matter. Probably I don't HAVE to be that careful, but I so choose. If I assume the worst and just avoid anything that might be problematic in less than ideal circumstances I'll feel more comfortable splurging on the occasional excursion into "safe" colors in a liner.

@Dick White Any chance your notebook includes info on which of those oxides are potentially toxic in small amounts in a glaze?

@Byrd Don't use the search engine on the site. For some bizarre reason it limits your results to stuff less than 2 years old. Use google and limit the search to ceramicartsdaily. Something like

@Min Wow, ask and ye shall receive! Thanks for that. Now all I have to do is figure out which ones are unacceptably (to me) toxic in a liner glaze LOL! Turns out not EVERYTHING can be found on Digital Fire. Just NEARLY everything. I've also learned what turned a bowl I glazed a weird mixture of purply-brown and gray. A glaze defect known as Boron Blue. Some people actually use that glaze on purpose to make that. I think its hideous. Now if I could only remember which glaze that was ... Probably I can identify it by the list of ingredients on the outside of the bucket. Now all I have to do is enter the entire list of glazes into the glaze calculator LOL!

@Hulk Just wondering - did you chatter the inside of that bowl? Also I've been doing a lot of thinking about liner glazes. I don't want to use any toxic substances AT ALL inside something people are going to be eating out of. At first I thought I could use Mason stains instead of things like cobalt and chromium and copper, but turns out there's no way to be sure of what they used to make the stains. But now I'm thinking, after seeing these bowls, maybe in at least some cases (where the clay body is pretty, unlike the old studio clay that turned out the color of zombie skin at anything above bisque) I could just use a clear. Otherwise I'm good with being limited to white or brown ("safe" colorants) for liner glazes. Is there any reason a clear glaze couldn't work as a liner glaze? Do colorants add anything towards cutlery marking and durability? Anti-crazing?

per Standard Clay

Yesterday and today I felt too grumpy to throw so I glazed some pieces I had that needed it. Why, thunk I, am I feeling grumpy about throwing? Because for weeks now I've been throwing with only porcelain (after experimenting with raku and Balcones Dark, one bowls worth each). And I've gotten BORED with it. This is news to me. I have developed a liking for variety in my clay, and that very recently. I've always been aimed in this direction (and have been counseled in the past NOT to try to work with multiple types of clay) so I think the impulse has been there but unrecognized as I struggled so with the studio clay, switching it up once in awhile with the B mix. So here's my suggestion for QoW - what clay body or bodies do you work with and what do you like about it/them? What is the impetus for working with one or multiple clay bodies? Corollary: do you make your own clay, and why?

@Callie Beller Diesel I don't care for the foam bats, pieces tend to sink unevenly on them. Larger pieces in particular. I haven't got the neoprene yet (its sitting in my Amazon cart pending figuring out whether or not we'll be moving soonish) but I'm thinking the 1/2" neoprene ought to be a decent replacement for the thicker foam bats when I need something to flip a platter over onto to protect the rim, and maybe able to leave it there for trimming. Thanks for the info, now I know the 1/8" stuff is what I need to make a sticky bat. Might try the 1/4" for bigger things, rather than the 1/2".

ok. Now I want to know how this works. At first I thought it must be melting point related but gold melts at a relatively low 1948F, which is around cone 04. Enquiring minds want to know ...

@Mark C. Yes and that is why we were taught to wire wedge 50 years ago. The wire would catch the odd twig or stone or other debris that might still be in the clay. But to find a literal TON of clay full of feldspar chunks and things that you can't just pull out, things that change the character of the clay, in "modern times" as it were, is kind of disconcerting. I had no idea this sort of things was much of a problem any more. I get why sponge bits end up in reclaim but I was surprised to find them in new clay LOL!

I've been finding bits of sponge in my porcelain, and I thought that was annoying. Now I'm afraid to buy clay ...

yup. Just don't use it anymore. The Ceramic Arts Network folks really need to update their glaze recipes in their freebie glaze pdfs to reflect what is affordably available, or available at all. ALL our materials are non renewable resources. Reclaiming clay is responsible, not a waste of time. its a waste of something that took millions of years to develop not to. Take a leaf from history. How many things relied on in the past have we already lost? Its only going to keep happening.

@LeeU I had one once, just didn't seem worthwhile to try to put that all up here what with a move being up in the air sorta imminently. Definitely will have one again wherever we finally light.

I'll for sure try that. If there's a way to prevent its better than trying to cure later. Besides which there is no cure for silicosis LOL! Though honestly I doubt I'd live long enough to contract it what with the little bit of wet sanding this would most likely entail. @Callie Beller Diesel I do try to burnish the grog back in after trimming but it does tend to pop back up during firing. The little red rib is exactly the one I use, sometimes the next size up if the piece is larger.

@Dick White Keeping in mind left/right is not an automatic thing for me - I wire wedge, then I do a few ram's head maneuvers, then what I do is turn it up in a clockwise direction so one side is now the top and one side is the bottom and its vaguely cone shaped. If I understand what you are saying I THINK that's the same as "turning it to the right". I do that automatically but without prior thought. Not sure why I get clockwise and counterclockwise but not left and right LOL! If that's the case then it seems I'm already doing what you advise? Which might explain why I haven't seemed to see any problems with "direction" of the spiral? (Because I've been doing it "right" by accident) I also round out the bottom as you say before slamming it on the bat. When you wire wedge, how much attention are you paying to the direction you slam the halves down? Another thing I never paid any attention to. Since seeing Michael Wendt and his stack and slam video where he makes a big deal about direction of the slabs, I make sure I don't lay the slabs crosswise across each other, but I can't do it the way he does it. My slab turns into a rectangle almost immediately. So I cut it whichever direction I need to to get it back to being squarish but lay the slabs back on top of each other with the cuts going the same direction, facing opposite directions from each other. So if I cut it N-S I stack it with the cuts still going N-S. If I cut it E-W (which is the way he ALWAYS does it and the way I start out) then I stack it that way too. Its as close as I can get to his way, I don't know how he keeps his slabs from going rectangular. I don't have a mounted wire so it takes longer but its my preferred method of wedging. I'll put up a mounted wire at a wedging station after the move, no point in doing it here.

Hulk posted these videos She mentions that most people are doing it backwards, then makes a point of showing the direction of the spiral and how it compresses the clay when you center it along the spiral (with the wheel turning COUNTERclockwise). Except I throw clockwise. Now mostly I wire wedge (aka "stack 'n slam") but lately I've been doing more ram's head wedging after wire wedging just to get it sort of cone shaped. I don't usually cone up and down. And this is why I think it doesn't matter what "direction" the spiral is going or even if you have one. I never have paid any attention to the direction of the clay when I slam that lump onto the bat. I would guess that most times it ends up opposite to the way the wheel turns because I wedge like a righty but throw like a lefty. I don't notice ANY DIFFERENCE AT ALL in how it centers and pulls, regardless of the wedging method. The only time I get s cracks is when I let things dry too fast (and they show up pre-bisque). I may have had something come out of a kiln cracked once, again, probably dried too fast but may not have compressed sufficiently. It's not a "thing" with me. I wedge to even the consistency of the clay out and to get rid of air bubbles. There isn't a spiral at all when you wire wedge and that's mostly what I do. And when I do ram's head, any spiral formed is going to go opposite to my direction of throw. None of this seems to matter. Any other lefties out there who have been unknowingly doing this? Though I suppose a real lefty (as opposed to a hybrid lefty-righty like me) might be wedging "backwards" as well as throwing "backwards" ... All this going round and round makes my head spin ... Seriously, I already have trouble telling my right from my left. I also have trouble lining things up like this - what direction the wheel is turning and what direction a "spiral" in wedged clay (ram's head or spiral) is going - I'm not sure I could even do that at all. I get real turned around real fast on these things. TOO COMPLICATED.

I was thinking he meant unholy bats like of the vampire persuasion ... and yes, I frequently overthink things LOL! (Yolks on me)

I was reading this: Which talks about fuming-on-purpose using cobalt salts which seems to be a bad idea but isn't exactly what I'm concerned about. We have been told not to use copper or cobalt washes at the studio because the studio manager says they can fume and damage other pieces, brick and shelves. So not cobalt salts, specifically he said copper and cobalt washes (he did not specifically say carbonate that I can recall, keeping in mind my recall is often somewhat suspect). Yet this guy uses OXIDE washes apparently without concern for possible fuming effects: Digitalfire notes of copper carbonate However re cupric oxide: I could not find any mention of fuming for cobalt oxide on digitalfire. However of cobalt carbonate he says: Further there are pictures of color contamination due to fuming from rather large chunks of copper carb and cobalt carb. All of Richard McColl's washes appear to be oxide forms (he says metallic oxides). So are the oxide forms "safe" from fuming issues and I only need to avoid the carbonate forms? If so why have the carbonate forms around at all if we can't put them in any of our kilns (excepting, apparently, raku, which possibly answers itself)? Are the carbonates also high risk for fuming in a glaze recipe?