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DanG

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About DanG

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  1. Slip mixture problems

    Its a pre-made slip that I bought so I've only stirred it (well), but I'll try siving it too, see if that helps. I was hoping that this 'scum' effect only sits on the surface but Im not sure thats the case as it seems to be forming on slip tapped from the bottom of the tub... maybe I'd have better luck if I made it myself??
  2. I am using a locally made slip called MFQ (Medium Fire Quartz) and I cant seem to get it to mix evenly (see pic left). Then I'm adding some stain to the slip and this problem with 'streaking' only seems to become more pronounced, such that the stain looks terrible! (see pic right). I am trying to achieve an even consistency and cant seem to do it. I contacted the manufacturers and they thought there was too much deflocculant in the original mixture, and I should try adding some dried clay to soak it up. I have tried adding a handful of two of pulverized dry clay into the slip (about 16 litres worth) and its not looking much different. Any help appreciated!
  3. Vanadium and food safety?

    I am using them as a body stain in casting slip called MFQ (mid fire quartz). Glaze firing will probably be cone 4 to 5. I havent had a chance to test this in the kiln yet but I will be aiming as high as I can to achieve full vitirification. The funny thing is that I can find NO official information line, no one who can certify these are food safe and theres no official advice on the matter here in Australia.. Its been very frustrating! I have met with some stain manufacters and thier customer relations know nothing whatsoever in relation to food saftey.. he had to write to a former boss who gave me the thumbs up but I still cant get any kind of official certification of saftey. Do you think I should only trust Zr encapsulted stains? Do you think a Zr stain would be ok even without a clear glaze over the top? I have been told that Cobalt is ok when combined with Si and Al as long as its under a clear glaze. I havent heard anything about Cobalt leeching under certain firing conditions, so Im keen for more information about this. I guess the best way is to have the pieces tested for leeching, which I will do. with thanks, Dan
  4. Great, will look out for these books. I have been thinking about the longevity of molds after I heard you can get about 50 casts from one before it is worn out. But I guess they are meant to be soft otherwise they wont interact with tthe slip properly. Ive just been using pottery plaster. cheers.
  5. Ok, thanks for the info. Glad to hear that molds can last that long too. I am still learning how best to make a mold that lasts... I noticed by accident that if you put a piece of bone dry plaster into the plaster of a newly cast mold (when its still liquid), it sucked the water out of the general mixture and made it rock hard. I havent experimented with this in the slip casting phase, but im going to try making some molds within a precast 'sleeve' and see if the harder cast effects the way it interacts with the slip.
  6. Ok, thanks for the good advice. What happens when you soak a mold? Does it reduce the life of the plaster or damage the interior surfaces? I have heard of people 'priming' a bone dry mold for use by dipping it in water for a few seconds, is this necessary or is it fine to use a bone dry mold?
  7. I was told a body stain I am wanting to use is food safe when fired. I have never used Vanadium before and although I understand its toxic in its unfired state, I was wondering what the feeling is about using it in a Zirconium stain formula? Its from Walker Ceramics in Melbourne: FW5307 Deep Sky Blue - V Zr (Vanadium, Zirconium dioxide) This is another stain possibilty: FW5359 Lavender - Co Cr Sn Zn (Cobalt oxide, Chromium oxide, Tin Oxide, Zinc oxide) How does this one compare to the Vanadium in terms of food safety? Is Vanadiuim any more toxic than using Cobalt? With thanks, Dan
  8. Hi, I was wondering if anyone has some advice on how to best clean slip residue from the delicate interior surfaces of a slip mold? I have tried soaking them in water for 1/2 an hour and this seems to have some effect, but Im not sure if this damages the plaster. Im a little nervous about directly wiping the inside of the mold as I dont want to damage them... any suggestions? with thanks, Dan
  9. Foodsafe stains?

    I just heard back from Rockwood and they said it was 100% foodsafe... but yes, I still feel a little unsure about that without testing. Im in Australia, maybe theres someone over here who can do this. BTW does cobalt have a reputation for leaching or for potential health problems in a fired state?
  10. Hi, Im new to using stains in tableware and have had a very frustrating time trying to determine if the stain I am using (or any other stain formula for that matter) can be certified as foodsafe and therefore safe to sell to the public. I am currently using a beautiful blue bought in Australia through Rockwood pigments called CT1503. The formula is Co Al, so I assume its a cobalt tint with alumina fluxing. I am using this stain as a BODY stain in mid fire slip and although the tableware will probably be clear glazed, I also want to be sure that even if theres sections uncoated in a clear glaze, that the fired body itself will not leach anything harmfull when used domestically AND I can provide some kind of cirtification to assure buyers that this is the case. Can anyone help point me in the right direction to the right authority or a source online by which I can determine these things? Ive contacted Rockwood but they seem to know less than anyone about this! Any help appreciated! Dan
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