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Min

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  1. If it hasn't been fired on yet then yes it can be dusty. It would just be a guess but the least expensive materials to use in a kiln/ batt wash would be kaolin and silica so if companies are trying to save money with the wash they supply they will load the wash up with that and skimp on alumina hydrate. There is a link below discussing kiln/batt wash with some tried and true recipes (it's towards the end of the link). Also, I would suggest wiping it back from the edge about 1 cm and wipe off any drips from the side of the shelf. https://community.ceramicartsdaily.org/topic/20981-frit-substitution-chart-orton-cone-charts-kiln-wash-recipes/
  2. @MsBeth, for the fondant molds are you using flexible silicone molds? I think there is a bit of confusion with the terminology being used, when you say "clay castings" is seems like you are using casting slip. But then "press the clay into the mold" sounds like you are using pugged soft clay. I have used flexible silicone molds and soft clay, I very lightly wiped the molds with veg oil then pressed the clay in then flexed the mold enough to have the clay pop out. There was a bit of distortion with the molds with undercuts but it was easily fixed since the clay was soft. Dusting molds with cornstarch is also an option, don't have to be concerned with airborne silica with it. Welcome to the forum.
  3. Slow. Both for firing up and cooling down. These pictures are from Digitalfire of lowfire ware, pots have cracked from uneven cooling, edges will have cooled faster than the middle area of the pieces. The way to avoid this is to have the cooling down go as evenly as possible. Slow the cooling down between 1150F - 950F, I go at 100F/hour through this zone with suspect work. There is negligible shrinkage, ie less than 1% between bone dry greenware and bisque firing to ^06- ^04, would be interesting to see data that shows refiring to a lower temp causes more shrinkage. edit: when having your piece in the kiln put it between shelves, not at the top or bottom of the kiln, this helps the heat even out also. I put rectangular or triangular kiln posts around the outside edge of the shelf also. (round posts can roll)
  4. If the food colouring is just to tint the raw slip then I would suggest using paste food colouring rather than the liquid, it goes much further.
  5. If all else fails MAGMA really should work to suspend iron spangles. I've noticed it can be listed as out of stock at Brackers quite often, if you decide to try it I would suggest emailing them and asking to let you know when it's back. It does thicken the glaze a fair bit and slows down the drying time so that needs to be taken into consideration. https://www.brackers.com/magma-miracle-anti-gravity-multipurpose-additive/
  6. Hi and welcome to the forum. Link to the Ceramics Arts Daily Tried and True Raku Glazes here if anyone uses any of these recipes. Giving this thread a bump, hopefully someone will chime in.
  7. If she isn’t absolutely 110% sure it’s a cone 10 clay then I would pass on this. This makes sense to fire the clay to maturity / cone 10 if she doesn’t plan on glazing it and it is indeed a cone 10 clay. She might want to leave it as bare clay or be planning on doing a cold finish on it. Firing to maturity would be a clearer way to describe what she wants rather than calling it a bisque firing. A mature body is far stronger than a bisque fired body.
  8. The concave then convex side design might also be contributing to it being pulled out of round.
  9. @Potpotpotter, slow cooling is different from a drop and hold/soak. With slow cooling the preprogrammed slow cooling schedule will be something like 9999 (freefall) from the last temperature in the program down to 1900F then 150F down to 1500F. If a glaze is already a matte without this slow cooling then by adding one you could very well end up with it being far more matte. This schedule is a basic slow cool for functional glazes, many people do their own custom slow cool schedules to suit their glazes. Slow cooling promotes certain glaze characteristics such as micro (matte glazes) or macro glaze crystals or visual textures within the glaze. It helps with some glazes and does nothing for others. Slow cooling is also useful for large pieces to help prevent dunting/cracking. A drop and hold/soak is helpful to help heal pinholes and blisters. The temperature you hold at will depend on how fluid the glaze is at certain temperatures. There are many causes of glaze pinholes and blisters, glaze thickness, application, glaze chemistry, bisque and glaze firing all can contribute to them.
  10. I wonder what would happen to it if you scraped some into hydrochloric acid? Interesting. https://www.sciencephoto.com/media/859757/view/iron-iii-oxide-in-water-and-in-hydrochloric-acid#:~:text=Left%3A rusty-red solid iron,HCl -> FeCl3 %2B H2O.
  11. There isn't a one size fits all firing schedule to fix pinholes and blisters but somewhere to start would be to drop 100F below your top temperature and hold there for 15 minutes. One other thing I do is for my kiln and my glazes it works to fire below the top temp and soak there to bring cone 6 down then do the drop and hold/soak, (I also do a slow cool for my satin matte glazes but that isn't necessary for many glazes). It can take a few firings to dial in what works for your kiln and glazes.
  12. I'm seeing a lot of plates made like this these days, it's a good way to make a plate with this type of design. I've got one bisque fired as a test but haven't got it glazed yet, it was really fast to make and I also like that it doesn't require any trimming. That nearly vertical edge is going to help prevent sagging/warping during the glaze fire compared to a flatter more horizontal rim. I would suggest putting one of yours in a glaze firing with no glaze on it, if it doesn't warp then it would suggest the glaze fit could be the problem. Welcome to the Forum.
  13. I stumbled across this Etsy listing where someone is selling feldspar granules, does this help? I know some people use chicken grit (not the oyster shell type) for big chunky inclusions in claybodies also. @PeterH, do you know of anywhere in the UK to buy it?
  14. Have you tried contacting them and asking if they have any other advice?
  15. From the article linked below from Charlie and Linda Riggs, they put the pot within minutes of applying the slip into the kiln and not to allow the slip to dry at all. Is this the way you are doing it also? I wonder if adding gum to the slip would help? https://ceramicartsnetwork.org/daily/article/Pop-Goes-the-Slip-Charlie-and-Linda-Riggs-Naked-Raku-Technique (behind a paywall but can access 3 free articles a month)
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