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puny earthling

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About puny earthling

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  1. Uneven Temperature In Small Gas Updraft Kiln

    just a brief update for anyone interested - my last glaze firing experienced similar problems to the last .I decided to increase the duration of reduction as a way of drawing out the flame through the kiln.This had a marginally beneficial effect .The temperature rise/speed near the end of the firing was up by 20C relative to the same time of the last glaze firing. However i pulled the plug on the firing after no increase in temperature could be affected at 1212C.The visible ^9 on the mid shelf had started to drop at this point.After cooling , an inspection of the bottom shelf showed ^12 had started to drop also.This again indicated about a 40-50C difference. I am planning to put in a flue directly above the kiln. This might again increase the draw within the kiln.This was recommended by a friend with experience in blacksmithing. The kiln up and till this point has had a 'tin' roof shelter sited about 90cm/3 feet above it (pitched at about 10degrees) with a couple of backing walls and a lot of heat is being trapped within this shelter.This might be causing 'circulation'/pressure problems. At least unwanted gases and smells will be driven off more efficiently Of course, reduction in shelf size is still a possibility but im resisting the temptation to throw many 'solutions' at the problem at the same time if it is going to be difficult to unpick what actually works -assuming that there is going to be a single solution . Life and pottery is a learning curve ...
  2. Uneven Temperature In Small Gas Updraft Kiln

    Thanks Neil ill see how it goes – maybe extend the flue too – not sure at the moment - A firing schedule was supplied with the original booklet – ive been following that – The maximum p.s.i. (as recommended ) is 3.5 at the end of the glaze firing. Ill let you know what happens via the forum when i get the opportunity to fire up again.
  3. Uneven Temperature In Small Gas Updraft Kiln

    sorry - suggestions
  4. Uneven Temperature In Small Gas Updraft Kiln

    Thanks Neil I was thinking that i needed to securely support the props holding up the top baffle shelf . As mentioned the kiln shelves are very small - i had even thought of create a ledge to support the non loading top baffle shelf and substitute it for ceramic fiber board so I could remove the props with more space for ware. The other obvious solution would be to get a bigger kiln - but as ive just started firing for myself it seemed a good idea to start small to get a handle on the process.. The new pyrometer and other equipment cost way more than the kiln itself infact and these could be used if /when I upscale . Any other suggests grateful received
  5. Uneven Temperature In Small Gas Updraft Kiln

    The burner is (i think) part of the original 1970s kiln equipment - so not venturi more like a sleeve that slides over an aperture. I have taken on board your good advice but im trying to have my cake and eat it at the same time by scalloping the edges of the shelf. This might be enough(???)and would allow me a bit more shelf space .see attachment. As ever with modifications the proof of the pudding is in the eating - excuse my food metaphors ,i must be getting hungry !
  6. Uneven Temperature In Small Gas Updraft Kiln

    It is possible that an extension to the flue might help draw the heat up too ?
  7. Uneven Temperature In Small Gas Updraft Kiln

    Thanks Neil – I was hoping you had another solution as the shelves are very small already ! The old manual which I hope you can read from the attachment recommends the shelves should off set from each other so the heat /flame can circulate – the bottom shelf away from the door but flush against the back wall – reversed for the second shelf and top baffle shelf again as the bottom shelf. Are you suggesting that space should be made all the way around and no shelf should be butted against the back wall or the case of the second shelf, the door? Would this apply to the top baffle shelf too ?
  8. Uneven Temperature In Small Gas Updraft Kiln

    more pics from me
  9. Uneven Temperature In Small Gas Updraft Kiln

    Ive got 2 photos at hand - one showing a bisque - the other the only glaze firing so far .The arrangement of the shelves are more or less the same as you can see . I have removed the top 'baffle' shelf in the glaze firing pic - ill send a few more pics a.s.a.p.
  10. Ive been doing pottery now for a few years and recently bought an old small ‘test’ up draft kiln with a capacity of 2 cubic feet and a single gas burner coming in from the side at the bottom ( an Australian Port-O-Kiln ‘Chameleon’ made about 1975) The problem I am finding is that of uneven temperature, something which I know is not uncommon in updraft kilns. Bricks are used as a floor but the rest is ceramic fibre.Two shelves can fit in to accommodate the height of tall mugs or two cereal bowls stacked rim to rim.A third top shelf is used as a baffle to help draw through the heat. The shelves have been placed at the same height (zig-zagging from back to front – again for heat flow )for three bisque and one glaze firing .The bottom shelf is sited just above the burner port opening. the second shelf up is approximately in the middle. I have a pyrometer monitoring the kiln located in the upper part of the kiln with the only spyhole also located in the upper part too. Reaching the projected target of ^10 (for the glaze firing) proved very difficult and concerned at my previous bisque firings which showed overbisqueing in the lower half of the kiln I stopped at 1214 Celsius. Cones on the two useable shelves showed ^9 starting to fall on the middle shelf and ^12 starting to fall on the bottom shelf ! -so approximately a 40 to 50 degree Celsius temperature disparity. Between the last Bisque and the latest Glaze firing I had reduced the size of the shelves along the sides and under the bottom shelf placed a small fire brick with it’s corner angled to split the flame. These measures were again designed to even out temperatures. If the shelves are reduced further this would obvious decrease the amount of ware I can fire in this very small kiln. Any suggestions to even out temperature ?
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