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PeterH last won the day on December 18 2016

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About PeterH

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  1. Hi, You might like to try this. You will need: - A metal canister open at one end a little bigger than your pot. - Two pieces of chipboard big enough to cover the end of the can. - A brick or two. - A newspaper about 1/4 inch thick. - A bucket of water. - Rubber bands or string. - Some charcoal. - A plastic shot glass or similar. - Some alcohol (UL meths, US ??) - Place the first piece of chipboard on the ground, with the tin on top. (This insulates the tin a bit.) - Cover the bottom of the can with charcoal. - Put the newspaper into the bucket of water to soak. - When it's getting nearly time to take the pot out of the kiln take the newspaper out of the water. Let it drip a bit then wrap it round the chipboard and secure it with the rubber bands or string. You should have a nice flat region of paper that will securely seal the lid of the can. - Fill the shot glass with meths. - Take the pot out of the kiln, and place it in the tin on top of the charcoal. Keep it away from the sides. - Rapidly: - Pour the meths into the tin. [H&S keep your head well clear, and wear something like a leather glove.] - Place the wet newspaper over the tin to fully seal it. - Put a brick or two on top to ensure the seal it good. WAIT until it cools. Then open the tin. You should be surprised how big a vacuum has been generated, and the tin should have left a clear compression ring in the newspaper. Hopefully the pot should be reduced. If it was a copper-matte "glaze" you may have reduced it so far that there is a layer of metallic copper. You can carefully reheat this in an oven and watch the colours develop. Unfortunately they fade with time. PS-1 A tin may be too weak and implode with the vacuum. I used stainless-steel tea-caddies from a charity shop. You may want to try reducing the degree of reduction. You might try less meths, open sooner, etc. PS-2 I've explained [sic] my limited understanding of copper-matte glazes in post #5 of http://community.ceramicartsdaily.org/topic/4701-copper-raku-matt-glaze/?hl=%2Bpeter+%2Bmatte&do=findComment&comment=42291 PP-3 Dedicated to the memory of Heath Robinson. https://businessenglishlessonplans.files.wordpress.com/2012/04/self-operating-napkin.png?w=300&h=211
  2. Your Experiences With Stain/s

    Hi, I seem to have failed to make myself clear. I don't know about "cleavage" numerical value ... from 100-150 or so Can you reference an accessible paper/article that has such numbers in it? I don't recognise the term optically negative Can you reference an accessible paper/article that uses the term? That way with some research I should be able to understand your points, and relate them to my current understanding of optics and crystallography. Regards, Peter
  3. Your Experiences With Stain/s

    Hi, At the moment I'm totally failing to relate your recent posting to my understanding of optics, and my sketchy understanding of crystallography. What would help me most is references to online papers that discuss the topics you mention. To verbalise my confusion: All minerals have a "cleavage" numerical value ... from 100-150 or so. - I cannot even image what units these cleavage numbers might be measured in, and I've always thought of cleavage and refraction as being essentially unrelated topics (bar the weak relationship through birefringence). - The only cleavage related "numbers" I can thing of are various cryptographic angles and Miller indices. I had to look up the name of the latter, but they are the bracketed triplets describing crystallographic planes; e.g (101). optically negative properties - A term I'm totally unfamiliar with, although a quick google might suggested that it might relate to birefringent crystals. - I totally failed to find anything linking "optical negativity" to matte/satin effects. Indeed I'd always believed that these were explained by the relative intensities of specular and diffuse reflection. As I said, I hope that reading some relevant papers can help me understand things better. Regards, Peter
  4. Raw Glazing At Cone 6-8?

    >"Glazes Cone 6 1240C" by Michael Bailey >they are rare and not cheap - £12.99 cover price, cheapest on Amazon £34...... You can save a little by using one of the bookshops indexed by bookfinder, at the moment the cheapest are £25.16 new, £22.26 s/h. http://tinyurl.com/j6pbh3m
  5. Porcelain

    Strange, the Scarva site doesn't seem to give any firing cone or temperature. http://www.scarva.com/en/Scarva-Nano-Colours-NPO032-Snow-White-Porcelain-Casting-Slip/m-5490.aspx Does it say anything on the container? If not, I'd try emailing Scarva (as they suggest under the "Description" tag of the referenced page).
  6. Raw Glazing At Cone 6-8?

    You might be interested in Fran Tristram's Single Firing: The Pros and Cons (Ceramics Handbooks). New and s/h copies can be found at reasonable prices http://tinyurl.com/jyucfyp
  7. Preamble - Firstly, I'm not the right person to ask. - Secondly, yes -- in theory -- its as complicated as that. - Thirdly, I don't think anybody normally does it that way. Direct top-of-the-head opinions on your points 1. Need a clay body that vitrifies at my firing temperature. If you want your work to be really functional, otherwise you're relying on the glaze for waterproofing. AFAIK you cannot do this with e/w as normally fired. 2. Know the expansion/contraction of the clay? You wish. AFAIK it even depends on how you've fired it. 3. Know my chosen glaze recipe is formulated correctly for the temperature and melts right and is going to be durable? Ideally. The glaze programs can help (assuming that its a glassy gaze). Things like under-firing a clear glaze to get a matt are not a good idea. Durability has received a lot more attention after Mastering Cone 6 Glazes by John Hesselberth and Ron Roy came out. 4. Know how a glaze recipe will act on my chosen clay (COE)? Some of the glaze programs can give you a estimate of the COE (assuming that it is a well-fired glassy glaze). AFAIK the general idea it to learn what the estimated-COE is for glazes that do successfully fit your body (as you fire it) and aim to formulate new glazes to something like that estimated-COE. In practice I suspect that there is a lot of grabbing recipes from somewhere, finding ones that they nearly fit, and line- blending to a good fit. [Good pragmatics are better than reliance on inadequate theory.] Remember to rub-in indian ink or something when looking for crazing it shows things up wonderfully, even fresh cracks. 5. Test it to be sure with some sort of extreme temperature/freezing/boiling test and durability test? If you're selling to the public it sounds like good insurance. For the hobbyist its still sounds like good practice, especially if you are using a porous body.
  8. I'm afraid not. Indeed counter-intuitive even crystalline silicon dioxide (quartz) and fused silicon dioxide (a glass) have quite different thermal expansion properties. So its not just the amount of SiO2 but also its chemical/crystallographic form. To emphasise the point, fused silica has a low thermal expansion and is the gold-standard for low-expansion heat-resistant laboratory glassware. On the other hand, quartz: Basically a lot of the SiO2 in a body is crystalline silica, and most SiO2 in a glaze is part of a glassy matrix. So its properties are quite different in the two situations. I'm afraid its back to the usual sources of information: https://digitalfire.com/4sight/glossary/glossary_coe_co-efficient_of_thermal_expansion.html https://digitalfire.com/4sight/troubleshooting/ceramic_troubleshooting_glaze_crazing.html
  9. It would be a pity to give up so soon. The deep texture seems such an integral part of those teapots, and Ginger gets it almost effortlessly with her texture mats. Just checking if the state of the clay was approximately as described by Ginger: http://gingersteele.blogspot.co.uk/2010/02/making-handbuilt-cup.html ...and you used a former to bend the slab : http://gingersteele.blogspot.co.uk/2010/02/step-5-making-cylinder-from-cup-blank.html Good luck.
  10. You may find this discussion -- and Norm's comments -- interesting: http://cone6pots.ning.com/forum/topics/6-oil-spot-mfa-thesis
  11. Googling teapots site:http://gingersteele.blogspot.co.uk suggests that the full details were never posted to the blog. However, the basic idea of the construction of the neck seems to be in: http://gingersteele.blogspot.co.uk/2011/05/building-new-teapot-form.html ... and quite a lot of relevant detail seems to be given when describing the construction of a cup: http://gingersteele.blogspot.co.uk/2010_02_01_archive.html PS I thought the pattern rang a bell, although Ginger's inspiration seems to be from dressmaking similar templates are sometimes used in pottery. https://circlematic.com/ https://circlematic.files.wordpress.com/2011/06/circlematic-article-pottery-making-illustrated.pdf
  12. You may find the latest freebie interesting, especially the article on emulating wood-fired results at cone 6 (oxidizing). https://t.e2ma.net/click/y4twu/qe4oos/6yeb6g
  13. Help! Frozen Studio!

    Minor point, I've read of problems with frozen Darvan. Googling gives Which is rather ambiguous.
  14. Crystals Forming

    John Britt's observations on crystals in his glaze buckets http://www.ceramicstoday.com/articles/flambe_magic.htm
  15. Technical Requirements Skutt Kiln

    Page 10 of this document might be relevant http://www.brackers.com/wp-content/uploads/2015/02/KilnMaster-Manual-2000_2006.pdf Might be the kiln sitter manual at http://www.paragonweb.com/files/manuals/acf1b.pdf I would wait for Neil's word on it, but I suspect that the sitter can switch more power than the kiln takes.