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PeterH

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  1. PeterH
    Fuller's Earth https://en.wikipedia.org/wiki/Fuller's_earth Fuller's earth is any clay material that has the capability to decolorize oil or other liquids without the use of harsh chemical treatment.[1][2] Fuller's earth typically consists of palygorskite (attapulgite) or bentonite.[1] Modern uses of fuller's earth include as absorbents for oil, grease, and animal waste (cat litter) and as a carrier for pesticides and fertilizers. Minor uses include filtering, clarifying, and decolorizing; active and inactive ingredient in beauty products; and as a filler in paint, plaster, adhesives, and pharmaceuticals.[1] It also has a number of uses in the film industry and on stage. Probably bad news, cat litter may often be calcium bentonite. See Digitalfire for the difference https://digitalfire.com/material/bentonite
  2. PeterH
    I'm pretty certain its mainly zinc oxide with a little ferric oxide. Probably quite close to calamine powder BP (the 99.5% zinc oxide, 0.5% ferric oxide). After all it is a skin treatment with a long pedigree.
  3. PeterH
    While waiting for knowledgeable replies ... From this picture of a casting table ... it looks like the main parts are * A table with rollers above the draining surface * A drain/holding tank * A tank stirrer motor and its propellers * A pump, hose and nozzle to move slip from the tank into the moulds You seem to have most of them. PS While the advantages of the table for mass-production look fairly obvious, I wonder if the cleanup overhead could become an issue for smaller batch sizes and/or lower throughput rates.
  4. PeterH
    Have you tried an indian-ink test? Easy enough to wipe off if there are no cracks.
  5. PeterH
    I think you misunderstand the point @Min was making. The artist she named must get their clay from somewhere, and perhaps they can help you get in touch with a supplier/source of pottery-grade clay.
  6. PeterH
    Don't you just love it when they overload an already overloaded name. Personally I find the Pubchem page https://pubchem.ncbi.nlm.nih.gov/compound/Calamine massively confusing as it gives Calamine lotion as a synonym. At least here in the UK Calamine lotion BP (British Pharmacopea) is zinc oxide with 0.5% ferric oxide -- and has been at least since at least the 1950s when it was widely used to treat sunburn. Anyway, what colour is the stuff you have? American Elements https://www.americanelements.com/zinc-iron-oxide-12063-19-3 give Fe2O4Zn as Zinc Iron Oxide (aka Zinc Ferrite) a brown solid. There is a picture at https://www.funcmater.com/zinc-iron-oxide-znfe2o4-powder.html While calamine powder BP (the 99.5% zinc oxide, 0.5% ferric oxide stuff) is decidedly pink https://m.jppharmaglobal.com/calamine-powder-bp-5307563.html While both pure zinc carbonate and pure zinc silicate are white
  7. PeterH
    Are you certain, and can you give a reference? Wiki gives two definitions of calamine, for a medication and a mineral. As a medication https://en.wikipedia.org/wiki/Calamine Calamine is a combination of zinc oxide and 0.5% ferric oxide (Fe2O3). As a mineral https://en.wikipedia.org/wiki/Calamine_(mineral) During the early 19th century it was discovered that what had been thought to be one ore was actually two distinct minerals: Zinc carbonate ZnCO3 or smithsonite and Zinc silicate Zn4Si2O7(OH)2·H2O or hemimorphite. PS Searches for calamine clay were largely uninformative, although this one for Calamine Powder says it is also known as hemimorphite (i.e. zinc silicate). https://www.thesoapkitchen.co.uk/calamine-powder ... and then gives a safety data sheet for 99.5% zinc carbonate and 0.5% ferric oxide!
  8. PeterH
    Not the way I read it, I think it's the clay/body that is tempered. https://dictionary.cambridge.org/dictionary/english/tempered tempered (adjective): limited or controlled, or made less extreme. So you achieve a tempered clay by adding temper to a less manageable one. From Hamer & Hamer Temper. An addition to clay which improves work-ability, e.g. sand and grog. Temper will also affect the fired result but it's introduction is essentially to assist forming and uniform drying.
  9. PeterH
    This gave 12 examples of types of temper, only one of which is grog. Temper (pottery) https://en.wikipedia.org/wiki/Temper_(pottery)
  10. PeterH
    Can you repeat your measurements of SG -- for both the slip and just water -- and report your raw data as well as your calculated SG. Making measurements for two liquids may help us discover where the error is occurring.
  11. PeterH
    I have a faint memory of stale 7-up being used as a medium by some Japanese potters. OILS AND MEDIUMS http://www.porcelainpainters.com/mediums.htm Sugar There are numerous recipes for sugar solutions to be used for pen work and for painting. The most common and easy medium is regular 7-Up. Everyone who paints or draws with sugar solutions seem to have their favorite mixture. The most common recipe is made by boiling 2 parts water with 1 part sugar, and using the syrup as a painting medium or thinned for pen work. It dries quickly and requires practice to gain consistency in brush work.
  12. PeterH
    Maybe of interest ... Temper (pottery) https://en.wikipedia.org/wiki/Temper_(pottery) A temper is a non-plastic material added to clay to prevent shrinkage and cracking during drying and firing of vessels made from the clay. ... and goes on to list 12 types I don't know how useful this definition is, or how widely it would be accepted. Note that the definition doesn't cover the use of "combustibles" such as coffee grounds or expanded perlite to add texture to the fired surface. Are there any additions to a flameware body purely to modify the fired thermal properties, rather than the shrinkage/cracking of the body during drying and firing? [Mica might be one?] PS It doesn't pass modern health & safety requirements -- and it has nothing to do with your questions -- but have you heard of Obvara Raku? Which I believe has it's origins in sealing porous cooking vessels. Marcia Selsor's Tips on Obvara Firing https://ceramicartsnetwork.org/daily/article/Marcia-Selsors-Tips-on-Obvara-Firing The obvara firing technique is a technique originally used to seal low fire pottery. It is believed to have originated in Eastern Europe during the Middle Ages.
  13. PeterH
    Looks like a nice book. A few sample pages available on amazon: https://tinyurl.com/mvayyb3f It looks like even 2nd hand copies are fairly pricey (change search to your location & currency): https://tinyurl.com/mr2wr7be
  14. PeterH
    In case it's of any help: Clays of Georgia for Ceramic Applications http://gspltd.ge/admin/editor/uploads/files/InterCeramics.pdf No experience in looking for clay myself, but perhaps these are of interest: Where is Clay Found? https://ancientpottery.how/where-is-clay-found/ How to Find Clay, the Definitive Guide https://ancientpottery.how/how-to-find-clay/ But if you do have a commercial source of real pottery clay, that seems the easiest option. Even if you have to re-hydrate it.
  15. PeterH
    You may find the results of a search for flameware in the Clay and Glaze Chemistry forum of interest.
  16. PeterH
    This sort of idea is often recommended: https://www.clayartcenter.org/clay-art-center-blog/2020/3/how-to-rehydrate-bone-dry-clay-easily Video of the same idea on a slightly smaller scale:
  17. PeterH
    I see some of your text as white letters on a black background, so it's not just you. an also generate this sort of text
  18. PeterH
    I suppose that it's just possible that some form of froth flotation is occurring, separating out some particles from the mix. It's certainly a technique widely used in mining/ore-extraction. https://en.wikipedia.org/wiki/Froth_flotation A hint that silicon carbide might be a candidate for this sort of extraction from silicon/silicates.
  19. PeterH
    Looking at the manual on Orton site (via https://www.ortonceramic.com/autofire-controllers-resources) I don't see a PLOG 0134 message mentioned, if you can't find one either it might be worth contacting Orton to find out what it means. However, with the exception of PLOG 0011, they all seem to imply a pretty significant problem has occurred. Hopefully simply as a consequence of a transient such as a power glitch. PS Pedantically the manual says that the error can be cleared. As you seem to have confirmed this doesn't mean that you can [always] just continue with the firing [well spotted].
  20. PeterH
    Sounds like a very rational analysis. It might be worth starting a new thread asking for recommendations of body/glaze combinations likely to meet those criteria. PS Have you seen these discussions on glaze chemistry at Digitalfire. (Not recommendations, just low-hanging google fruit.) G1916Q - Low Fire Highly-Expansion-Adjustable Transparent https://digitalfire.com/recipe/g1916q G1916M Cone 06-04 Base Glaze https://digitalfire.com/article/g1916m+cone+06-04+base+glaze G3879 - Cone 04+ UltraClear Glossy Base https://digitalfire.com/recipe/g3879
  21. PeterH
    Can you repeat the measurement process again? Once with t-sig and once with water?
  22. PeterH
    Can we check your figures, as SG<1 seems rather unlikely. What are you measuring, and what where the values?
  23. PeterH
    How are you measuring the SG? I've read several times that you cannot/shouldn't rely on hydrometers when measuring slips (i.e liquids with complex rheology). If you did use a hydrometer can you recheck using a syringe and scale?
  24. PeterH
    I'm uncertain what types of glaze you are interested in, which influences what "chemistries" you will need to know. For example are you interested in vice-free "reliable" glazes or those with "character"? Which might mean a choice between: - a liner glaze and one or more base-glazes that you can colour to taste. - several different glazes with radically different properties and constituents: e.g. oil-spot, crackle, "wood-ash", ...
  25. PeterH
    You might also find the second half of Ian Currie's book Stoneware Glazes of interest. https://wiki.glazy.org/t/ian-curries-stoneware-glazes/367.html It discusses the constitution of a variety of "classical" glazes. Which might be considered to occupy some "sweet spots" in interaction space.
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