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Kiln venting

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  • Kiln venting

    Hi all

    I have a question about kiln venting

    I have a Rohde Ecotop kiln, sited next to a window. It has an air intake feature at the bottom and a side exhaust hole. The latter feeds into an 'exhaust fume system' - basically just a metal pipe screwed to the side of the kiln to which is connected a flexible metal hose which goes out the window.

    So far, so good, except that using the 'exhaust fume system' prevents me from plugging up the exhaust vent during a firing. This is specifically stated in the Instruction manual which says:

    "The exhaust socket has been designed to prevent the emitted heat from radiating against walls, surfaces or objects. If you attach the exhaust socket onto the kiln, the
    exhaust opening cannot be closed. If you wish to close the exhaust opening during firing you should not attach the socket."

    This seems like a design fault to me: ie if I want to close the vent during the firing, I have to accept the non-venting of fumes!

    I would be interested in any comments on this - also on the recommended temperatures for closing the air intake and/or the exhaust vent during a stoneware firing to 1250C

    Thanks in advance


    (for anyone interested, pictures of the system can be view in the manual downloadable from the CTM Potters Supplies site under Electric Top Loader. They're on pages 6-7)

  • #2
    Are you talking about venting the kiln itself. If so normally all firings are vented to about 500, to drive off excess moisture (yes there are fumes in this). So you need to be able to vent the room it is in as well. Before I bark up the wrong tree, am I on the right road here?


    • #3
      Mmmm, have just read the manual, looks like that attachment is a simple way to vent the kiln when firing. Nothing to do with the term vent as in airing your kiln. There is an air supply slide that you can open, which you will need to as I said up to 500, although they recommend 600-700. When you have reached that temp then you should close off the air supply, the slide (given term) in this kiln. Have you allocated the slide on it yet? As for the attachment, I would go by where the kiln is housed. I can give more advise if needed, stoneware to bisq firings-to glaze etc. Let me know.


      • #4
        Ok thanks MB - perhaps I've misunderstood this: are you saying that I should simply close the air supply slide when the temperature reaches 500 or so - and leave the exhaust vent in the side open throughout the firing? If so, does this give me an oxidation firing for stoneware temperatures?

        The confusion comes about because Rohde also supply a small firebrick plug which loosely fits into the exhaust vent - though not with the fume system attached, as explained above! - I was assuming I had to insert this (at what temperature?) to bring about a reduction firing, in addition to closing the air supply slide. Or is this wrong?


        • #5
          Not sure, if the vent system is for letting fumes out then I am sure that it will not vent the kiln.

          The slide will vent the kiln and will normally have to be closed at 500oc.

          Is the plug for use if you do not use the vent system, or is it as well as?


          • #6
            Sorry now I'm confused.

            If the vent system is for letting fumes out then I am sure it will not let air in. That job is for the slide.

            You let air in through the slide and close the slide at 500oc.

            Is the plug for use if you do not use the vent system, or is it as well as?


            • #7
              good question, MB, and not one that appears to be answered in the manual!

              I'd assumed that the slide was to let air in only (thereby creating an air flow via the pots through to the exhaust). I'd further assumed that by closing it at 500 I would be cutting off this flow - this seems to be stated in the manual. Whether this produces a reduction atmosphere or not is not at all clear.

              However, it seems I could then additionally plug the exhaust (NB not a tight fit, anyway), as envisaged in the passage from the manual I quoted earlier, thereby reducing the oxygen levels in the kiln even further. Not sure what effect this would have but I suppose it's worth a try in theory.


              • #8
                I would be tempted to do a test with and without, costly I know. Keep a date/time/materials log of every thing you do.

                There are many,many ways to get the results you are looking for, working in pottery is very experimental. Don't stress too much, have fun!!!!!!!!!

                Good luck, let me know how it goes. Have you tried to speak to CTM about the kiln?


                • #9
                  I'm certain you won't achive a reduction atmosphere with the bung in and the bottom air vent closed. The whole point of letting a small amount of air in to the kiln from the bottom, is to displace the moisture given up from the clay, if it is not removed it will which shorten the life of your elements somewhat.



                  • #10
                    Hello - I found this thread and wonder if I could ask a similar question. After you close the air intake on a Rhode Ecotop kiln (at 500 or 600-700), should you use the fire-clay sealing plug that Rhode provide to close the exhaust vent, or leave it open for the rest of the firing. Really ... when, if at all, should you plug the air exhaust? Why are the plugs provided? (Yes, I realise that this kiln does oxidation firing, and that none of this would cause a reduction atmosphere in an electric kiln.). Thank you so much for any help.