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Without going into too specific details to follow the ASTM... for cups and mugs put a cup of cool water in the corner of a microwave then with the empty test sample mug run it for 2 minutes at full power. Handle temp must not exceed 60C/140F and any of the other surfaces 121C/250F. Before commencing test the test pieces must be submerged in room temp water for 12 hours and also pass the ASTM 325F oven to water test. (which I don't have) Slightly different times and temps for plates etc.

I just ran a 1 minute microwave test with 4 pots with the following clay bodies: Standard 365 cone 6 English porcelain Standard 266 black clay A medium-brown cone 10 stoneware with grog A red body, fired around cone 3. After microwaving for 1 minute and measuring the temperature of the piece in the middle, using a laser pyrometer: The porcelain and the cone 10 body both came out around 140F. Kinda hot, but I could get them out of the microwave. The 266 black hit 170F, too hot to handle. The red body was over 220F. Here's the really interesting thing, though: in all cases, the unglazed areas were a lot hotter than the glazed areas. When I measured down the side of the piece, they were all cooler at the top than they were at the bottom, presumably because they all have unglazed bottoms. The red clay pot was glazed on the inside and about 3/4 of the way down on the outside, and at the very bottom of the outside where it was unglazed, it measured over 260F. In all cases, the bottom inside was at least 30 degrees hotter than further up the walls. So glaze on both sides seems to have a pretty big effect on how hot the pot gets. @Kelly in AK if that plate was glazed on the bottom like most commercial plates are, that may explain why it stayed cool in the microwave. Another odd thing: If I microwaved several at a time, they didn't get as hot- just like when you have more food in the microwave you have to run it longer. But the unglazed areas heated up almost as much as when I ran them alone. Strange stuff. So iron in the body, glaze, vitrification? I don't know if the red body got hotter because of the iron in it or because it's not fully vitrified, or both? The Standard 266 has a lot of iron, maybe more than the red body, but it's more vitrified than the red, so is that why it didn't get as hot? Or did the red get hotter because it has more unglazed area? Lots of mysteries here. Having something in the pot that has to get heated up definitely slows down the heating of the pot. I microwave a mug of water 3-4 times a week in my studio for tea. It's made of Standard 365 cone 6 English porcelain, and every day I pull it out of the microwave by the handle with no problem.

I bought my top loader electric kiln secondhand and it came with a stand that has always seemed a bit too small. Some of the bricks have started crumbling and while it’s working, i feel like it’s not happy on this stand. I’ve alwys had the stand on top of a paving slab and I’m wondering if I can get a few household bricks and use them and the slab instead of the stand? I’ve got some of the basic engineering bricks with holes in. Would this be okay? Using it in my house so I’m quite nervous

Thank you so much for the info! That is very helpful. The 2nd link works for me so idk, but it is a low magnesium recipe so I thought it might be a good alternative for brighter colors. I'll skip over colors requiring zinc for now since my brain isn't ready to swap fluxes else just yet.

I wouldn’t use either of those glazes if you are new to glaze chemistry as it would be necessary to remove some of the other fluxes in order to add zinc. If you just added zinc then the glaze would have more flux than needed to create a balanced glaze. Result would be an excessively fluid glaze. Glazes high in magnesium tend to have a more muted response to colourants than those without high levels of it and blues from cobalt lean more towards purple tones. Yes, zircopax will give more of an opaque glaze, with or without stains. Starting at around 5% addition will show, 10% will be opaque on most bodies. A green stain that contains chrome when put in a glaze containing zinc will most often give an unpleasant brown. Your second link didn’t work for me. Welcome to the forum.

I tried an experiment. I microwaved five unglazed items made with five different clay bodies along with a beaker of water. None of these have ever been exposed to water. Humidity exposure is minimal (kept inside and in New Mexico where it is a fairly dry weather). Readings using a laser thermometer after 1 minute in the microwave: Cashmere and Ochre 100F Marilyn's BOD and Chocolate 120F IronStone 210F These are all cone 5/6 clay bodies by New Mexico Clay. I am guessing, based on their appearance, that Cashmere (a white porcelain/stoneware mix like B-mix) and Ochre (a light tan) have the lowest iron content. Marilyn's BOD (a red-brown stoneware) and Chocolate (Dark Hershey brown smooth clay, almost black) have a bit more, again based on appearance. Ironstone is advertised as having so much iron that a magnet will stick to it which I tested and it's true! Fortunately, it wasn't so much iron as to fry my microwave! I did not do the presoak as prescribed by ASTM because I was more interested in the effects of the iron in the clay body. Even without the presoak, per ATSM C1607-06, the Ironstone would NOT be considered microwave safe. Maybe someday, I'll make mugs out of Ironstone and the others and then run the mug test complete with presoak.

10 would be the most I would try to center on it. I've done that. It can do it, but it would prefer smaller amounts. Also bear in mind that the wheel is fairly lightweight, so it's easy to slide it around when centering that much clay. You have to have it up against something solid in order to keep it from moving.

5 burner Olympic 7 cu.ft., 3 ring Torchbearer kiln currently fueled by natural gas. Could be converted to propane with appropriate burners. All shelves and posts as is plus thermocouple. $500 or best offer. Location Richmond B.C. Contact Lin via Private Message. (click on my name then the little envelope at the top of the page to send me a message)

Nice work on the medallion, just out of curiosity what cone does your glaze fire at. I use some underglazes on my murals and fire at C5, I have to use four coats to keep the color from fading away at that temp. Denice

I am a all porcelain shopcone 10 firing gas. I would make my own wash and remove with a wet sponge before firing any commercial wash as it usually poor quality. Speaking of quailty wash I noticed on the Advander shelves (kiln shelve.com ) site they use the same formula as I posted years ago 1/2 alumina hydrate 1/4 epk 1/4 calcined EPK or (glowmax) I apply a VERY thin coat with a paint roller after shelves get warm in sun and when dry scrap the edges of wash

Great to hear! Now if they were only ever in stock anywhere lol… I’m currently fitting out an entire studio and never have had as much of a problem with so many things being out of stock/backordered for months as I am having with ceramics stuff right now.

Recipe #1 (minus the cobalt): https://glazy.org/recipes/151716 Recipe #2, low magnesium, haven't tested yet: https://glazy.org/recipes/472422 I'm new to pottery and making glaze. The 1st recipe covered my dark clay well and made a nice texture so I've ordered mason stains to play with. I've seen a very vague mention of magnesium not playing well with some so I'm looking for insight before starting. The main info I have is on the mason stain reference page here. The two green shades I ordered say they're best without zinc and I saw a correlation with magnesium, so it's possible I might have trouble with green...? A couple of the colors say they'd do better with some zinc in the recipe, the rest I ordered are fine with or without it. Does anyone know how much should be added? I don't see any zinc on the analysis for either recipe. Since the top recipe makes white rather than clear, is it best to keep it as-is when wanting vibrant colors or should I remove the zircopax? I read somewhere that mixing into white will make more pastel colors, which is actually what I want to start with. A test I saw without zircopax didn't cover darker clay so I don't see the recipe working without it. Thanks for any thoughts you have on this! It's just a hobby during the little free time I have very little understanding of the chemistry. Colors ordered: walnut, dark red, canary yellow, French green, grass green, turquoise, copen blue, onxy, Saturn orange, lavender and coral.

Hi all, Does anyone know of open pottery studios in the Malmo/Kristianstad area of Sweden? We've just relocated to the area and I'm looking for a group studio or maybe even to enroll in a school so I can have access to studio and kilns. I'm not experienced with running kilns so need a place to fire and create work. Thanks so much :)

Yep, our porcelain plucks. But kiln wash is super easy, super smooth or a little alumina works just fine for us. Cone 10 furniture plucks as well but dipping the ends of furniture in kiln wash is super effective and lasts many, many firings. The weight of each load is 30-60 % lighter than ordinary shelves so to us they are worth it in reduced energy alone.

Does anyone here use porcelain with the advancers? The website says you need to use kiln wash if you do, but they look like a pain to kiln wash since they are so smooth and non-absorbent. Wonder how big of an issue this is in practice…

Hi , I want to buy the Speedball Artista pottery wheel. ( I am a hobbyist) and can just about throw 6-7 lbs of clay. I wanted to know if The Artista table model can center at least 10 lbs of clay. That is my maximum limit. thank you.

I also hold my trimming tools with both hands, but I use the left hand to rotate the tool in my hand to the position I want instead of rotating the wrist of the hand holding the tool. best, Pres

I've a particle board "bat" just thick enough to cover the pins for trimming*. I'm using clay to hold the wares in place - rather a lot, for I need both hands to use trimming tools; the right wants to be in charge (control) but needs the left for support**. I grab a handful, for it will need re-wetting throughout the session. For narrow topped wares, there's an (ever growing) collection of tapered vessels to set the ware in, which I then fix to the "bat" with clay. ...so far, each time I think it's time to fashion a chuck, I've found somewhat else that will work. Much as a Giffin Grip would seem ideal for me, I'm accustomed to my process. So far, I think of somewhat else I'd rather have for the $... *which eliminates the striking hazard of bare bat pins... **Oh, they (hands) work, just not the same as they were decades ago. Our adaptations/workarounds, we (err, I) become accustomed and don't always notice "what's missing" if it's not right in front of us!

I await the discussion with great interest. PS It's almost certainly irrelevant, but I'll mention an odd-ball method I once read about for reducing the adhesion between the casting and the mould. They were making a medical device that needed to be X-ray transparent, so the thin body was basically alumina and totally non-plastic. They found that mould release was more practicable if they first cast a very thin layer of paper fiber into the mould. It was obviously a high-value item, so mould life may not have been an issue. I don't think that there was much detail in the mould either.

I use to donate pieces a couple of times a year, one was for AIDS and the other Hunger. I never got any business from them and I thought they treated the artist badly, I finally quit in protest with other artist who were treated badly by the committee. I didn't have any problems . my piece sold but the work that didn't got dumped on the sidewalk the day after the auction. One of my friends who is a well known metal sculptor had his work thrown out. His sculpture covered home is in tourist guide books. Denice

Refiring is need, speckle clay have a lot of impurities that need to burn out, I use several clay's that have a excess of impurities. I fire a slow C04 to keep my glazes clean. Denice

Neoprene disc stuck to the wheelhead with a little water for the vast majority of my pots, no clay wads. For bowls and platters wider than the wheelhead I use a large batt that I glued high density upholstery foam to and put that on a damp Xiem BatMate knockoff. Never felt the need for a Giffin Grip.

I have a seperate trimming station its a small Brent Model A wheel with a few Griffen Grips. One is set up for regular sliders the other is set up for arms. Back when I was really producing tons of wares I could just snap one off and use the right one without time switching parts. Now I'm doing less and its not critical . I also have the griffen huge platter trimmer hanging on the wall but I have not used it in a few years so it may have to go up for sale. Not making mondo huge platters anymore. These are all time savers if you are in the business of pottery production

Morgan Post placement still needs to be about the same. Its not about warping but the thermo load.When loading the bottom the stilts need to be lined up as the thermo load is great with all that weight at bottom, as you get to the top of the kiln it is not as critical. Its always best to line them up when you can. Even advancers cannot take huge offsets due to weight at high temps. They can break from that stress of uneven thermo loading.You have been lucky so far would be my guess.I have had corners crack odd from uneven sharp posts even thougfh they are lined up underneath. Of course my cone 11 load is often 5+ feet tall so the weight is great . In terms of more wares from this shelves you now know they pay for themselves pretty fast with extra space. And your back is better from less weight loading. Its amazing really as they are all upside other than the cost which is recouped the more you fire.

Produced by means that Marge Para was paid to mold, cast, and fire the bisques for the person who commissioned the sculpture from Becky Turner, which was Melissa Meader who's hosting the Show. Every year she selects an artist to do a relief sculpture for her show, then usually Marge molds and produces the bisques. Marge glazes most of them in 'original finish' runs of set colors like teal, green, blue, purple, etc. Those are given away as the primary awards along with rosettes to the various champions that are awarded. Then a small number are sent to guest artists like myself to be custom glazed in realistic colors. These last pieces are then auctioned off to raise funds to benefit the show. It costs many thousands of dollars to host a show, pay for the rental space, food, set up and taking it down, insurance, etc. She also flies in her judges from all over the country so there are a lot of costs involved. There are many such shows I take part in. Some like Melissas are for ceramics only, others are for equine sculpture in general and may have various categories for ceramics, resins, plastics, metal casts, etc. I sometimes get flown out by show hosts to judge at such events, or like Breyerfest in Lexington, KY, there are /several/ major shows scheduled back to back each day one after another. One for ceramics only, one for resins, one is the National Championships. Each one of these events commission sculptors to produce original designs for their awards. So, because producing equine ceramics comprises so many skill sets, it's not at all unusual that we often do collaborations of a great many people. One might sculpt a piece, then pays for someone else to mold and produce it. Then the bisques are sent out to various ceramists who custom glaze them in many various colors, techniques and finishes. It's quite rare for someone to do what I do, to sculpt, mold, cast, and glaze pieces start to finish because it involves so many skill sets that can take quite literally a life time to master each one. Those who do all of the steps usually build and employ entire teams of people to work together to do so. Therefor I have /mostly/ done finish work on other sculptor's pieces over the past five decades but these days I'm focusing more on sculpting, molding and casting my own sculptures to finish and share out with other finishing artists. I've been doing my own sculptures since about 1984 but now I'm focusing on it more as my full time effort. If you felt up to sculpting pieces like this you can reach out to ANY kind of show - such as shows for cats, dogs, poultry, dolls, ceramics shows, whatever and see if they wanted to commission you to do the awards for the show. Usually plaques, medallions, or actual trophy pieces. Some do these awards in bronze but bronze is super pricy. So doing them in ceramics is a lower cost option - and it doesn't look bad on your resume to have shows you have produced awards for! Or if you aren't into sculpting, but you felt up to molding and producing the bisques and maybe glazing, you can team up with a sculptor to offer that service!