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@davidh4976, I was thinking more about the 450F temp and crazing. Is the ASTM554 test still valid if the body cracks but the glaze doesn't?

Pinched your fingers yet? (yup, I've done that a few times )

My guess would be it's because of different reflected indexes between the glazed and unglazed surfaces while in the microwave.

A few Artista threads; there are at least three long time Forum regulars who own(ed) and use(d) an Artista: Artista Potter's Wheel Question - Equipment Use and Repair - Ceramic Arts Daily Community Speedball Artista Potters Wheel - Equipment Use and Repair - Ceramic Arts Daily Community Speedball Artista Pottery Wheel - Good Or Not ? - Studio Operations and Making Work - Ceramic Arts Daily Community

The chain won't short out a thermocouple connection permanently, it'll just make it read funny while it's touching. Double check your thermocouple connections at both the thermocouple end and the controller end. Make sure the +/- wires are in the correct positions. On type K thermocouples, yellow is positive, red it negative. Maker sure the thermocouple isn't too close to the metal casing on the kiln.

These pieces were all dry, right out of the cabinet.

For those that haven't seen it:

In reduction the oxygen in the iron oxide is removed leaving the pure form of iron FE. Ive done heavy reduction on pieces sprayed with straight iron oxide and come up with a silver gray finish.

Well, can you show the interior? Looks like a Min glazing technique.:-)))

Thanks for the input ! May go for the Shimpo v lite .

It is coincidence that @davidh4976 mentioned a clay body so high in iron that a magnet will stick to it and I received in the mail today the strongest magnets I’ve ever seen. So, of course I had to play. My clay is a local iron rich earthenware that vitrifies at cone 03. Not all the pots do this, apparently only the ones that are reduced heavily and fired to maturity.

I question the testing using the same piece for each subsequent heat increment as each cycle will stress/shock the glaze. I know that's the point but I agree with Hansen's take on this. I sometimes go 300F/ice water, then 315F/ice water then 325F/ice water. If a glaze doesn't stress craze from this I don't think it will with everyday normal (sane) usage. 450F to ice water IMHO is far too extreme! We are after all making ceramics, not metal bakeware. It does seem logical to soak the test piece for 12 hours after a reasonable stress/shock testing though. edit: In the past I did try the boiling water / ice water testing, had a glaze that passed it so went ahead and glazed a load of pots with it which later went on to craze. I'm sticking with the oven/ice water test, greater difference in temp therefore a harsher test, either the one above or just 3 sets of samples at 315F.

Yes, @davidh4976, ASTM C554 is the “prerequisite” test for test C1607. And I agree, putting pots through the worst I can imagine a reasonable person doing in their kitchen gives sufficient information as to how they’ll hold up. I believe it’s important to use your own work, it helps you understand what you’re expecting of people.

You should talk to Orton about shorting out that connection

Hi and welcome! Stains are fun to work with, especially for us dark clay users. And the reference chart you’ve already found is a very good reference is this section of Digitalfire. Tony identifies the stain by number, which is a good practice as there are 3 different numbered stains with the name “dark red” and they all have slightly different chemistry.Tony’s got examples of the Canary Yellow and Turquoise in a magnesium matte glaze base, so you can see how those 2 respond, at least. Speaking of recipes: the second link you’ve shared comes back as a “does not exist” error. If this is a recipe on your own page, make sure it’s published so we can see it. Zircopax won’t make the colours pastel: glaze colour theory doesn’t work the same as paint. If anything, it’ll make it brighter and more saturated, because more of the colour is reflected back to your eyes.

Maybe you mean ASTM 554? It calls for three passes of going from 250F to room temperature water without crazing. Repeat at +25F increments up to 450F. Crazing fails the test. Too much work for me! I just rely on three passes of boiling water to ice water to determine whether it's going to craze or not. It is a little bit more of a cheat for me because boiling water at my altitude is only 199F. Although the microwave test calls for doing ASTM 554 first, to me, the two tests seem mostly independent. If you are going to determine whether a piece is microwave safe, microwaving it and seeing if it gets too hot seems to be enough for me.

I also saw this on other test pieces I have microwaved. I believe it was because water had absorbed through the foot of the cup and was present in the lower part of the cup but had not been drawn up into the upper parts of the cup. The water heats up pretty fast.

Excited that I retired this load and we changed the breaker and it worked. I do think after the advice I received here we are going to make some changes. Thanks again everyone

Hi folks, So I finally pulled the trigger on an Orton Autofire Slide single-zone controller for my L&L J230. I've attempted my first 06 bisque firing with it today but keep getting an error saying "Thermocouple response" and it aborts the firing after about 10 minutes, at around 200 degrees. Here's a little info: I set it with an 8 hour preheat last night, as some of the pieces weren't bone dry. All switches on high, and all lights for each section of kiln were turning off and on as they should. Downdraft vent on the whole time. Checked this morning and had an error saying "Failed to heat". Temp was showing about 200 degrees. I did have the lid propped and the peeps out for the first part of the firing, so thought that may have contributed to it not heating as it should. Closed lid and plugged the peep holes. Restarted the firing, and started getting the "Thermocouple Response" error and the firings aborting after about 8-10 minutes. Went to inspect the thermocouple from the outside and noticed I may have made a really stupid mistake. Apparently one of the chains that are attached to the side of the kiln and the lid to keep the lid from opening too far had laid across the thermocouple terminals (not something I'd even thought about, but will be sure to check for in the future!). Hoping this was the issue I tried restarting the firing again, but no change. Snugged down the wires to the thermocouple but still no change. I'm concerned I may have damaged the thermocouple or potentially shorted something out with the chain. It still seems to be reading the temperature of the kiln, so hopefully this isn't the case. Any thoughts or input as to how I might diagnose and resolve this issue? I'll probably try to call Orton in the morning, but I'm on a super tight deadline to get these pieces ready for this weekend, so if I can get this firing done tonight it would be great. I guess I can always just use the kiln sitter but it would be nice to not have to babysit the kiln all night. Thank you very much in advance!

Final photo! Got my old Seeley's porcelain slip all reconstituted beautifully. Here are the medallions poured and cleaned up and bisque fired for the show awards. The three smallest are intended to be jewelry pendants. All of these can be kept as porcelain bisques or custom glazed at some later time. Now back to casting more of them for my event in July!

The kiln needs air flow under it so you don't overheat the floor, and the bottom of the kiln should be at least as far from the floor as the stand makes it, usually about 8 inches. Cinder blocks work, but you have to orient them so the holes are facing horizontal, so air can flow through them. Or you can put a sturdy piece of sheet metal under the kiln, on the stand, to support the crumbling bricks.

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.