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Tim T

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About Tim T

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    http://www.tim-thornton.com

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    Nether Wallop, England

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  1. Hi guys, Just in case you are wondering why the link to the survey has changed, the moderators objected to the links in it to my web site etc., so I've had to make an expurgated version of the survey just for posting here, with a new link. For the missing bits, if you want them, see below. Tim
  2. Hi, With the many questions (and variable quality answers) on topics such as the toxicity of materials, food safety and other aspects concerning hazards and good practice for the potter in their studio, and the safety of the finished piece for the customer, I've started working on two books on the subject. The first is for the studio, concerning things like toxic materials, dust and silicosis, kiln firing and other hazards, how to assess and mitigate them. The second is for the finished work, looking at food/microwave/dishwasher safety, thermal shock in pieces for oven and cooking use (in
  3. One tp I've found is not to wash the ash. It is a lot of work, and removes soluble fluxes. Unwashed ash glazed generally have a halo round the edge of the glaze, but I don't mind that, and although a bit more caustic putting on a pair of gloves is a lot less work than washing the ash! Perhaps try it on the inside of a bowl, so it won't run off the pot and upset the others in the studio!
  4. I've decided that doing my own kiln controller would be an interesting project, but too much of a distraction from making pots. This was exacerbated by my (now ex) kiln controller deciding to overfire to about 1330 (in a kiln rated to 1300!). In the soak, when the elements came on, the temperature readout dropped so they stayed on till it got to the target of 1290, then cut out and the temperature readout immediately jumped up to 1330 and the kiln cooled down to 1285, then the elements came on and the temperature immediately dropped. I guess the elements were causing a voltage drop which then
  5. Hi Nerd, Just picking up on this thread again. I've done a bit of work looking at clays for water content and plasticity, using the Atterberg test for moisture content for upper and lower plastic limits. Also, in the absence of a ny proper lab kit for this, a drop test to measure the actual plasticity - make up a 50mm ball, drop from a height of 2m into a bowl, and measure the diameter, plus take a piece and measure the MC - not perfect but indicative. What I initially assumed was that a wide moisture range would correspond to a high level of plasticity, but as I test more clays I find this i
  6. Not wanting to complicate things too much, but I don't think you can just look at the formula without also looking at particle sizes - yes for a common set of raw materials (and so particle sizes) the formula will give a comparison, but for example if you changed to coarse sand for the silica that would make a big difference to the dynamics of the firing, and so the result. This is a good discussion on the topic: https://studiopotter.org/pdfs/sp28_1_sohngen.pdf Because particle size is so important to the handling properties of the clay, there is inevitably a compromise between what is wanted
  7. Ju00Ls, Firing costs is one aspect, and another is to combine with temperature and monitor when kiln elements are getting towards end of life. Being out in the sticks power can be a bit dodgy - power cuts typically every couple of months - so I thought it may be useful to monitor V as well as A. I'm using a power monitoring IC as they are cheaper than using discrete components, and the processing is all done on the IC, so less coding for me and also less load on my CPU. Also, the intention is to build it up into monitoring temperature, and then controlling the kiln, but do one step at a ti
  8. Not directly part of the kiln controller, but having just had a problem with power supply to the kiln (see separate post) I'm starting work on a power monitor. At work we're doing something stuff with an ESP286 (Arduino compatible but with built-in WiFi) I was thinking of using that combined with one of the AC power monitoring ICs to do all the maths for measuring Volts, Amps etc, to an app for displaying and logging data. Although the original trigger was to just detect power failures, by doing this I can monitor V and A, plus total power consumed during a firing etc, so check what is happeni
  9. There's a lot more cars around than pottery kilns, even if you just take owners who want to work on them themselves, so I don't think you'll make your fortune with a kiln controller!
  10. I don't think it matters whether you dump dry or wet, the point is to be aware of the toxins you may be letting loose into the environment and the cumulative effect of this and similar actions on the environment.
  11. You need to keep separate your clean clay for recycling, and things like glaze slops and other non-recyclable material. If your clay is reasonably wet, you can add some water to it, leave to soak, then put it onto a plaster bat and wedge it. If too dry for this to work, let it dry out fully before adding water (I keep 2 buckets on the go, one for each). As you may have seen from many of the posts in ere about toxicity, some of the glaze materials used are toxic, and should not just be poured down the drain or into the garden - you don't want them feeding the vegetables or getting into the
  12. If you get tall thin ones they read more accurately than low dumpy ones, as 1mm change in height is a lower change in volume - but they are also easier to knock over!
  13. A few things here. I don't think the discussion so far has highlighted sufficiently the effect of firing temperatures on element life If you just bisque fire or do earthenware, you are working well below the melting point of the elements, and replacing kiln elements is a very rare occurence. Mine lasted a couple of years without needing replacing, and then I decided to play with oil spot glazes, so firing to 1290C and soaking for 2 or 3 hours, and now for this work I have to treat the elements as something needing replacing regularly (I haven't been organised enough to count the number of
  14. Another thought here is to go from the normal relays in the kiln to using a thyristor/solid state relay. This is because, when not at full whack, the normal relays generally have a maximum in.off cycle time of at least 30 seconds, which causes temperature fluctuations in the elements. According to Kanthal, this can reduce their life by as much as 20%. However this will be most noticeable as you fire closer to 1300 and have long soak times - if you just do earthenware you probably won't notice the difference. They aren't just a straight plug-in replacement, though, and a bit more knowledge of
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