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tomhumf

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Everything posted by tomhumf

  1. I've just seen this, I do use cones and get to cone ^8 but not much above 1200C usually, maybe my thermocouple is in a cold spot - it's above the burner port so probably.
  2. Hmm Babs do you just use stains with frit and bentonite, no other ingredients? Bill, thanks for that but I only expect these pieces to be a small portion of my work so don't think a special firing at ^04 would be practical with my biggish kiln.
  3. I'm wanting to use stains to paint with brushes over a base glaze. I want the colours to be as intense as possible. They would be used on food surfaces. I've tried just paining them straight on before but they don't melt. I just did a test mixing a stain with frit 3134 in varying amounts. The idea being I would get the most melt for least colour reduction. I'm getting some bubbles where it's thickest on most of the samples though. I'm guessing this method is probably a bad idea? My base glaze isn't very clear so perhaps I'll try and work on a clear base that will work over my main glazes - otherwise any suggestions of the best mediums to add stains to for rich over glaze painting? It would be nice to have the option of adding more flux somehow to control how much the stains bleed out into the main white glaze underneath. You can see from this test they are all very controlled - would prefer a bit more melty look I think. I'm firing to ^8 reduction. Also I'm not sure how easy the brush work is going to be with glaze on glaze - especially as im not very good as brushwork yet!
  4. Hmm, it's not black just fired in reduction and the lighting was bad in those photos. I guess the glaze could be having an affect... It's the clay on the image, my probe doesnt go much above 1200 so I think it should be ok in theory. https://www.valentineclays.co.uk/product/stoneware-special-fleck I'm about to fire some more with a slightly wider and further out foot ring, will see what happens with those. Thanks
  5. Thanks @Mark C. Would you think wider like thicker footring, or wider like further to the outside? These are cone 8. @Callie Beller Diesel thanks, I could try that but wouldn't that be more if the centre was slumping? If anything the centre is lifting a bit, maybe it's slumping in the centre first in the firing I guess. @Minok I'll look into that
  6. I've been struggling with this for a while. My dinner plates look fine after trimming and bisque firing. Then after the glaze firing a lot of them flop over and I get a bump on the inside around the outside of where the footing is underneath. Sorry if that doesn't make sense, I can't really get a photo of it. Basically after drying the inside is a smooth curve, but after glaze firing the inside has a bump in the curve. I throw them to 12" from 2kg of clay. After trimming they are around 0.8 - 1kg, after glaze firing they are 700 - 800g. The foot ring is trimmed to 8" at the widest point. I try and trim all areas to the same thickness. There doesn't seem to be a relation between weight and warping, even some of the thinnest ones are ok. Any ideas? Maybe more clay, wider foot ring? Photo is good one on right, flopped on left
  7. Oh thanks I didn't see duplicate. Hmm, Ok thanks. I haven't tried it on other bodies, this clay is fairly high in iron I think. I'll do that if I ever got other clay in.
  8. Hi, I stumbled on this glaze when trying various additions to my base glaze. It's very similar to a glaze I used before with titanium dioxide and copper carb as colourants. That one went green and I had assumed because of the copper carb. This glaze goes green without any copper - just rutile additions. Adding copper as well seem to have very little effect. Can anyone suggest what's causing this? Also, would you say the base colour without rutile looks like a celadon? Otherwise how would you describe it? There's some more info on the glazy page https://glazy.org/recipes/148698 Thanks!
  9. I did take your previous replies on board however - I've been continuing to fire reduction with tape on burner ports, as I can't get rich yellow flames just with closing the damper. I don't know if it's my kiln design or what...but closing damper enough for yellow flames means temp starts to drop - I can't increase gas anymore at this point. I'm actually getting a little too heavy reduction though overall by reducing hard at 900C for one hour, with 4 of the burner air holes taped. I'm wondering the best option for lighter reduction. If I reduce without the tape on burners, just using the damper and the flames from peeps are blue will I still get some reduction? I'm thinking of reducing tape to 2 holes instead of 4 next firing - it will be quite a full load so don't want to risk having it all oxidised.
  10. I've been struggling with this glaze for a while. Firing to cone 7-8 in reduction with speckled stoneware. I'm aiming for a silky matt smooth surface, which happens occasionally and on small test tiles. https://glazy.org/recipes/119355 The worst example shows the base of bowl, it's like the iron in the clay is poking out, surface feels almost like sandpaper. There's lots of very tiny pinhole / bubbles - not sure how you'd describe them. I seem to get better results where I think the tests were hotter ( inside of dish), but I can still see some similar surface imperfections. I'm going to try more 3134 next time, and maybe more soda feldspar and less Wollastonite in case the high calcium is a problem. It does seem like there is a lot of frit already for this cone though? Any ideas welcome please.
  11. I made a similar kiln, not sure the thread is updated to what I do now. I use a brick on the top of chimney as my damper . I fire in oxidation, reduction then neutral. I get probably within half a cone top to bottom.
  12. @liambesaw ok thanks. Maybe I'll just run the emptier tanks on their own to start firings, and pigtail the fuller ones when I need the extra volume.
  13. They are 47kg tanks. I have a thread about my kiln, don't think it's the one you mention though, it's a 10 cubic ft internal space running on one burner. It's about 12 hours firing. Probably not half inch of ice actually, but very icy. I may be able to reduce gas usage in future, still working on my glaze schedule. I don't have a problem with icing tanks when bisque firing for 12 hours. Nobody responded to my question about if the gas would equalise between tanks if I connect them together. I've watched a couple of videos about propane valves and it seems they would work both ways, so a full tank would fill an emptier one. Can you confirm @liambesaw as you do it this way? Thanks
  14. Hmm, they don't shut off, I just start to loose pressure. It's running at about 1.5bar in reduction. It's not just a freeze line, I get about half inch of ice building up by the time I need to switch, over half way up the tank. I thought linking them would mean half the gas used from each one so they would freeze up half as quickly.
  15. I get through quite a bit of gas firing my kiln with one burner, the tanks are freezing up while they are still half full. It's not really practical to run water on them. I think if I connect two together they will stay thawed for longer, I'm not sure the best way. I've found this connector , which I would use with my existing regulator connected after the T junction. https://www.ebay.co.uk/itm/New-LP-Propane-Gas-90Cm-2-way-Hose-Connector-Coupler-of-Two-Gas-Tanks-Acme-Nut-/264275507385?_trksid=p2349624.m46890.l49292 May be stupid question, but do the valves on top of tanks only work one way? If I have mismatched tanks I'd want the emptier one to run out, not get filled up by the fuller one. Would it matter that gas would be at full pressure before the T junction, or would it be better to have a regulator joined at the valve of each tank?
  16. Thanks Bill, I did try initially to reduce with just the damper. It seemed to not work very well, i.e loosing temp or blue flames from the spy holes. I'm right to think blue flames would give bad reduction? Maybe I just needed to crank the gas more or something. I did have positive pressure during the hour reduction - yellow flame from bottom peep. I can see you point about keeping above neutral for the later stage. I was a bit worried about having enough gas in this case so wanted to make sure I completed the firing.
  17. I just wanted to update this thread with my latest results. I have been using the kiln mostly just for bisque firings since I last wrote - these have been going fine. The previous glaze firings didn't turn out very well - didn't really have successful reduction. I've read a bit more and found this article really helpful http://ceramicsfieldguide.org/pdf/val-cushing-handouts/special-extras/Cushing-HighFireProcess.pdf Using that as a guide I started getting great results from my other tiny kiln. Basically oxidised to start, reducing hard @900C for around an hour, then firing in a neutral atmosphere until the cones drop. I had previously misunderstood the neutral atmosphere to be just when there aren't flames from the chimney. Now I check it with the bottom spy hole and a lighted paper on the outside, if the flame is sucked in the kiln is oxidised, the flame just stays burning up if the atmosphere is neutral, or will be pushed away from kiln in reduction. To check this on the 10 cubit ft kiln I've made a spy hole right near the bottom on the opposite side from the burner port. I put in 15 glaze tests (same glaze and clay on all) one at the front, middle and back of each 5 shelves. ( the top shelf was only half length so I put the end tests on props at the same height. The photo has the tests with back of shelves on the right, and arrange top to bottom as in kiln. I put the cones at the front, middle and back on the bottom, middle and top shelves. In the reduction phase I found I needed to tape some of the air inlet holes on my burner up to get a yellow reducing flame from the kiln, I also closed up the burner port as much as possible with slices of kiln brick. I'd be interested to know if people think these tests are over- reduced? I think I could make the reduction phase 45 mins next time probably. The kiln was climbing pretty well in neutral atmosphere, I could probably get to cone 10 if I want. The cones are a bit uneven but I guess a slightly longer firing might even them out more. Overall I'm really happy with this test and the few pots I put in. I will probably try another small firing before loading it fully with orders. One thing I was worried about while firing was the flames were blue from the main spy hole during the neutral phase, most things I've read says the flames should be green / yellow. It seems this wasn't a problem though as long as the pressure at the bottom spy hole wasn't sucking flames in. This is my not very accurate firing log in time / temp C. Glaze, cone 7 1 kiln on, damper 3" 2 50 3.17 200 4 313 4.45 450 6.15 650 damper 2" 7 777 Went to Aldi and gas lost pressure so changed tanks 8 700 9 893 damper 1" , gas 1½ bar, top 4 holes burner taped and one bottom . Burner port doors closed as possible 10 909 Tank froze, Switch tanks. Take all tape off burner. Damper 1½" gas 1 bar, just no flame from bottom peep. light blue flame from main spy. Open burner port door. Small flame from chimney. 10.50 1000 11.16 1065 11.36 1090 11.59 1119 12.20 1136 12.42 1165 1.03 1186 1.22 1203 1.30 1215 kiln off
  18. I've only been full time for around 6 months but it's going well so far. It sounds like you don't need to worry about making speed, I think I throw slower than that. Like others have said it's all the other stuff that sucks time. I start to finish about 50 pots a week, they are mostly customised so take longer to finish than plain pots. I sell everything online , for me getting my dispatch setup efficient was key. I used to spend ages sorting labels and taking everything to the post office, waiting in cues...Now I've got some dispatch software that combines my Etsy and Shopify orders in one place and prints royal mail labels. Then all parcels get picked up at my house. Also building a larger kiln has made me massively more efficient. I personally think social media is not necessary, it sucks time. If you have good products and start getting good reviews on Etsy, you will be flooded with sales. I have too many. If you have a website that is good you'll get traffic without social media.
  19. Bill - I do fire to cones and temperature, it was only hitting around 1210C with cone 7s down before. I've done two firings since posting this message. Both times I've got kiln up higher in temp - around 1230C and held for 30mins. The cones are very melted, it might be nearer cone 8 now. All pots so far have been problem free, glaze is a bit shinier, so it must just have been underfiring before I think. I do prefer the more Matt look. I may try increasing clay, reducing quartz with new firing style. I'm not sure if that might bring this problem back though.
  20. Hmm top temp could be an issue. I usually only get up to around 1210C which I know is low for cone 7, even though cones are well melted. I did hold for a half hour at top temp in this firing, and downfire to 1100. I don't fire super slow - around 8 hours so not sure why top temp is low. I bisque fire in a larger gas kiln, its about 12 hour bisque with 3 hours between 700C and 900C.
  21. Thanks, I always use the same clay and bisque fire. I fire to cone 7, but it's a little gas kiln so it could be temp differences. I guess more frit then...
  22. Hi, I wonder if someone can say if this is crawling or not? I'll post pictures in a minute. It works fine on some pots but not others. It gives little bare patches and also some bubbly bits occasionally. I'm thinking of increasing the frit or maybe thinning glaze a bit... Thanks. Blue wollastonite 9 Frit 3134 17 China clay 22 quartz 13 soda feldspar 30 talc 9 0 £0.00 0 £0.00 cobalt oxide 0 £0.00 0.2 Zirc Silicate 7
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