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About tomhumf

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    Sheffield, UK

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  1. Thanks, I'm still early stages, I'm in the UK though and I guess you're US.
  2. Ok thanks. My plans for burner port is currently 3" X 4" opening. I plan the chimney at 6" X 6" inside with 3" thick walls.
  3. I've had to put this on hold due to money but, now have the funds ready... This is my latest plan after your suggestions and some other reading. 9" thick walls, will probably do 4.5 " arch with fiber over the top and 9" thick floor. I'm hoping to make it work with one burner, my biggest concern from this plan is the space around shelves. It's probably a bit tight top and bottom ( 1½" ) and too much at the flue side (4½") but can't see a better way without having to cut a load of bricks. I plan 8 courses for walls, which would give about 10cu ft total internal space with arch.
  4. @Bill Kielb Thanks so much, will have to re read that a few times for it all to sink in I think! Lots of good stuff
  5. It's iron Great video, is the longer version online somewhere? Id be interested to see it if so. I have a couple of questions... the attached photo is of my latest firing. Same glaze but a bit more frit this time, all the mugs were in same firing. I'm wondering if the differences in look is because I didn't ' fill the kiln and not have any dead spots' like you say. In this firing I reduced between 1600F and 1900F, and was in oxidation ( I think ) after that up to cone 7. I will probably try and follow your schedule next time, and maybe reduce more in your heavy reduction section. I'm a bit unsure of how best to get the temp to climb while under heavy reduction. My method of reducing my little electric kiln conversion is to shut off the chimney to about 1 inch gap. This creates a reduction flame out of chimney and peeps but makes it hard to gain temp - I understand this is because its burning inefficiently. But if I increase the gas burner power it's just going to burn more inefficiently? ...but if i reduce gas it will go back to oxidation I guess I'm missing some of the control of larger kilns, and I don't really understand the terms primary and secondary air. From what I understand they the air mixed at burner port (primary) and air available at chimney (secondary) ? Wish I could get an oxy probe but no budget for that unfortunately. What happens if you reduce under 1400? Not that I want to but seems like something really bad would happen...? @Mark C. I understand your point about cold spots / oxidised spots. Hopefully I will be able to minimise them in some way, I guess a lot is down to kiln design which probably isn't great in my case. @neilestrick I'm stuck with gas firing really at the moment. I understand every pot won't be the same. I'm happy with 75% of the pots out of this lot, just wish I could prevent the really boring white ones ( like 3rd right and 3rd left) in the photo.
  6. Lots of Dremel love here, I will get one I think. Not sure about them being expensive, the low range ones are £60 / ~ $70? On Amazon...I suppose compared to knock offs they are expensive?
  7. Ocassionally I unload the kiln and find some little chunks of glaze/ clay / god knows what on my pots. This is despite looking over/ sanding the bisque carefully, sieving glazes etc. I'm thinking of getting a Dremel to tidy up these sharp lumps. I don't currently have anything like a sander or grinder. I only grind bases with sandpaper or rubbing two pots together. If you think dremels are a good idea, what kind bits would I need? I'm looking at the Dremel 3000 which has a few included. I guess you need a hard rough one to remove material then a polishing bit? Thanks!
  8. I can see how you think glaze thickness is the issue. I have keep glaze the same, and same dipping time for ages while trying different firing cycles. I thought the thickness might be an issue myself and thinned the glaze a little for the one on left. Not sure if that means thicker glaze would be better....but I've had plenty of bad results with the previously thicker glaze too. I will try take a pic before i go on holiday of the bases, they are very similar. The right one is very slightly darker but not really dark like on the plate base.
  9. I've been struggling with this glaze for a while, I really like it when it works... It's a speckled clay with white glaze I've developed on all these photos, fired in a tiny gas kiln. I like the mug on the right - the glaze breaks on the rim, handle and throwing lines, and there's a bit of speckle showing. I don't like the left one at all, the glaze is melted but very boring. I like the yarn bowl results - similar to the right mug. These have all been fired with between 30 mins and 1 hour reduction at around 1500 F - then completing the firing in a neutral atmosphere. I've played around with a lot of schedules. Some just holding on reduction at around that temp, some climbing through it in reduction. I can't seem to pin down what temp or amount / length of reduction is giving this look. Perhaps it's more to do with final temperature though I've aimed to fire everything to cone 7 consistently. The plate was done in the one firing where I began reduction at 1800F and stayed in reduction until the end of firing. I don't like this look as much. Although the speckle is very pronounced I don't like how the glaze has lost its whiteness. ( I think I may have splattered iron on the surface and painted the rim with iron on this one, so not a perfect comparison) I've started making better notes in my firings, but maybe someone might know if the look I'm after is to do with reduction or simply temperature? Or any other hints Thanks!
  10. Ok thanks I will just wait until I can get some proper cones when I come back then.
  11. I'm going on holiday in a couple of days and wanted to get a firing in before I go. I ran out of cones and I don't have time to order more before I go. I just found some cone 7 minibars that I used to use in my electric kiln sitter. Nowadays I'm now firing a gas kiln. If I stick them in some clay do you think they will bend at the same rate as a normal cone 7 witness cone?
  12. I've been working a travel mug design for a while. It is basically a tapered tall cup with a lip that fits a silicone sip lid. My biggest problem has been how to insulate it enough so you can hold really hot liquids comfortably without a handle. My current design uses a couple of circles of clay attached where you would naturally grab the cup. I have carved lines in them to aid with air flow. The cups are still a little hot to hold straight after pouring though. I have some commercially made travel cups that have a double wall as insulation but that isn't going to be possible with a thrown form. I'm wondering if I could make a thick slip to go on the outside. In the slip I would add some kind of combustible - little paper balls? Then as they burn out I'd get lots of little air pockets for insulation. I'm firing a gas kiln outside so fumes wouldn't really be a problem. Is this a crazy idea. Any other suggestions?
  13. Would this be because the arch is stronger and will be more durable over time? I've ordered the Olsen book so will have a read of that. My brick supplier says they can cut bricks to my spec, the only ready cut arch bricks I could find elsewhere are super expensive. Otherwise I'm thinking if I calculate the angles I could set up a jig and hand cut them... I don't really want to use fiber, but 2 arch layers seems super hard to calculate. Would one layer layed in 9" thickness be a silly idea? I see them done in houses this way round.
  14. Wow ok, that's a lot more bricks than I thought then. My supplier does the 3 x 4.5 x 9 ones so those are what I'll use. For the roof I suppose it would be easiest to do a one layer arch with them stood up @ 9" thick...or would you do a 2 layer of 4.5" arch? I'm a bit worried how difficult it will be to cut the arch bricks to get a good seal.
  15. Thanks Neil, it seems it would work if I understand those charts correctly. I assume when it refers to 9" walls it means 9" long bricks layed with a 3" wall thickness... Thinking of what bricks to use - I can get soft bricks and 42% alumina hard bricks. I was thinking to use hard bricks as the kiln floor, layed with 4.5" thickness, and as the first layer of bag wall / firebox. And then soft bricks everywhere else. I wonder if one layer of hard bricks at the base will give enough insulation, it would be light concrete blocks underneath that.
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