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Everything posted by Min

  1. Some underglazes come with warnings to cover with a glaze in order to be used on "dinner ware" surfaces. Spectrum 300 series can be used as either an underglaze or over a glaze majolica style at both cone 04 or 6.
  2. Earlier this month Mayco bought out the colour division of Duncan Enterprises. Sounds like they will be selling off remaining inventory and then some of the products will be rebranded while others will be discontinued. Just a heads up if you use Duncan products, might be an idea to check if what you are currently using will still be available in the future. From a facebook page from Mayco: "As you may have heard, Mayco has acquired the ceramic fired and non-fired color lines of Duncan Enterprises, effective November 2, 2020. Over the next 90 days, Mayco will start manufacturing “The Best
  3. @Purpleglaaze, if you are using a brushing glaze you can lightly sponge on a thinned down coat of glaze, let that dry thoroughly then brush on the remaining coats. Other thing about glazing over unfired underglaze (ug) is the ug contains gums that can hinder the amount of glaze taken up by the bisque. When you bisque fire ugs the gums burn out so the bisque takes on the glaze easier. There are ugs that can flux enough at bisque 04 that also can hinder the glaze application. Like its always said, test, test, test. Welcome to the forum!
  4. It came with just the one thermocouple but when I replaced the controller I decided on using 2. The boards now have the option of 1,2 or 3 thermocouples being wired up.
  5. Try a triaxial with a 50:50 mix of boron frit (or gerstley borate) and nepheline syenite as one point, your clay as second point and ash as the third point. If you haven't done a triaxial before chart below shows how to blend. Basically you will be having 3 ingredients which will be blended together in different ratios. Might take few triaxials to get it nailed down but definitely should be doable. If it's too fluid then decrease the flux in a line blend. Fire your tests on waster pieces of clay and/or use little bowl shaped test pieces and just glaze the insides.
  6. I wouldn't call it a major fail at all, they didn't tip onto the elements, didn't hit the bricks, didn't make a glaze mess on the shelf. I think you were very lucky with how it turned out, not a major fail. You lost some pieces, no biggie.
  7. I wouldn't use your regular cone 6 clay, it's still going to slump, more and more so with subsequent firings. April 2020 C.M. has a kiln post recipe from Jeff Diehl that he uses up to cone 12, EPK 25, XX Saggar 25 and grog (30 mesh) 50. Another recipe that would probably work would be a mullite setter mix. C.M. June 2017 article from Glynnis Lessing making kiln setters ^10 using 20 Talc, 25 Tennessee Ball clay and 55 Mullite (100 mesh).
  8. I'm not seeing the pinholes as being a big issue at all if the clay is vitrified. Look at Japanese Shino wares, pinholes are part of the aesthetic. If you don't want the pinholes on the next one then try lightly spritzing the bisque with water about 5 minutes before you glaze it. The dampened bisque will take up less glaze so when the glaze runs down it won't create such a thick layer.
  9. Easy suggestion for a QoTW following last weeks question of the week; would you give up any of the technology you use in ceramics now and go back to a simpler not as technology advanced method? Maybe starting with defining the term technology as it pertains to ceramics making.
  10. If you aren't glazing it then no it isn't necessary to re bisque fire. If you are glazing the iron can smudge if not bisqued on first. Do a test tile at the same time, try a heavy dark application, a medium one and a light one, try one coat and two or three, see what happens. If you glaze over an iron wash or apply the wash over a glaze if there is a high amount of calcium in the glaze the iron will tend to "bleach" out and go a straw colour.
  11. Hi @grumpykidstudio , I swapped it out for a Bartlett V6 controller from Pottery Supply House / Euclids. They had a used one that I got a bit of a discount on. I use it as a bisque only kiln since the elements are such a pain to replace in this kiln (non segmented) and use 2 thermocouples. The board fit without having to alter the box. The original controller had very limited options and I was using it for glaze firing originally but after a little while a lot of the readout was illegible as parts of the numbers and letters blanked out and it had some stuck pads. I'ld contact Tuckers, send the
  12. @Earthandwater, post a picture of what you are concerned about.
  13. Put the witness cones in front of a spy/peep hole and check that you can see them before starting the kiln. Wearing kiln safety glasses to protect your eyes monitor the witness cones towards the end of the firing. If the witness cone isn't as bent as you want it when the kiln sitter trips off then you need to lift the trip arm up about 45degrees and press the white button to restart the kiln. Check the witness cone about every 10 minutes until it is bent how you want it then press the trip arm all the way down to shut off the kiln. If you find the reverse is happening with a cone 6 firing and
  14. From wiki the issue seems to be not the in the ground form of chromite but what happens to it during the mining process. Perhaps I'm reading this wrong but from what I'm taking from it is the chromite during the processing of it under normal processing conditions and not a wet and non-oxygenated atmosphere converts to the hexavalent state. From the Health Effects section of this link: "Chromite ore is found in underground conditions. Therefore, when exposed to aboveground conditions, various effects will occur. Some of these effects include weathering and oxidation. The element chromium i
  15. @Naomi what Bill and Sorce said plus if you have lotion or something oily on your hands when handling the bisque or if the bisque is dusty there won't be a good lay-down of the glaze which can turn into it crawling away from those areas.
  16. An old upright fridge or freezer stripped down but with the door seal still intact works well.
  17. Iron chromite is a synonym for iron chromate. If you have to have a similar colour response it's far safer to use iron oxide + chrome oxide. Iron chromate is highly toxic through absorption, inhalation and ingesting. I agree with Mark, take it to the toxic waste drop off. @kristinanoel, some reading on chrome and it's various forms below. https://pubchem.ncbi.nlm.nih.gov/compound/Iron_II_-chromite https://digitalfire.com/4sight/hazards/ceramic_hazard_chromium_compounds_toxicology_330.html edit: my comment about iron chromite being a synonym for iron chromate is referring t
  18. If you can find the composition of the stains it would be helpful. Not all stains are compatible with all glazes nor claybodies. My hunch would be the Deep Crimson and the Pink are chrome tin stains (they employ chrome and tin to make the colour). Chrome tin stains need high calcium and preferably low alumina, in a claybody you will have a high level of alumina and the calcium is probably not nearly high enough for the colour to develop. For pink I would look for a manganese alumina based stain.
  19. Do raw glaze/single fire? Looks like outgassing from the claybody causing pinholes, the 3134 in the recipe will be an early melter, if the glaze seals over the body before the gasses have had time to escape (either during a bisque or in the earlier stages of a glaze firing) the gasses will blow through the glaze and cause the kinds of craters and pinholes like in your photos. If you do bisque fire post your firing schedule, might need slowing down.
  20. If this is an open lowfire slip Darvan 811 might not be the best choice, from Vanderbilt Minerals: "DARVAN 811 is used in vitreous and semivitreous bodies, and in glazes. A slip deflocculated with DARVAN 811 provides the following advantages over the conventional soda-ash, sodium silicate system used to disperse ceramic bodies" Darvan 7 might be a better choice.
  21. Newsprint works better than paper towels, even if the water evaporates from the newsprint it stays wrinkled. This is just a quick but not too accurate test, a more accurate one would be to weigh the pot when it's fresh from the kiln (I know you can't do that now) then put it a saucepan with water and do a low boil for 8 hours then let it cool overnight in the water. Dry all the surface water off then reweigh. The wet weight minus the dry weight divided by the dry weight, with the result multiplied by 100 will give the percentage of absorption of the clay body at that temperature. Under 1.5 - 2
  22. @GreyBird had a samples tested at Mineral Labs, I don't know how much they would charge for what you are looking for, she paid $500- for comprehensive testing. Thread with the information she got is here.
  23. @PeterH, I got an unsafe warning when I went to open the link you posted. Is it the same as this? 3 areas of Norway marine clay samples at various depths. https://www.ecsmge-2019.com/uploads/2/1/7/9/21790806/0265-ecsmge-2019_paniagua.pdf
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