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Everything posted by Min

  1. are these engobes ?

    Both a slip and an engobe can change the surface texture and colour of the clay to which it’s applied to. An engobe is similar to a slip but is made with less clay content than a slip. Typically slips are formulated to be similar to a claybody in chemistry (or the clay body itself is used to make a slip). Since there is less clay in an engobe it is going to shrink less than a slip therefore can be used on leather-hard, dry greenware or bisque without shrinkage problems. Slips work best when applied as soon as possible to the still wet or damp clay pot so the slip and the pot shrink together. Engobes have higher flux content than slips to help create a bond between the clay surface and the engobe whereas a slip bonds to the surface through the interface between the damp clay and the slip. Slips don't rely on additional fluxes to bond with the pot. Since there is more flux in an engobe than a slip the fired surface can be more vitreous than a slip . I think part of the confusion comes from the term "vitreous slip" which by definition it is an engobe and not a slip. Underglazes can have a clay base or a frit base but with either they still have the properties of an engobe more than a slip. Others may have different definitions, this is my understanding of the terms.
  2. Away for a few days, cabin up the coast, wifi can be spotty where I'm going. 

    1. terrim8


      Have a nice time!


  3. Newbie without bentonite

    Whiting is calcium carbonate which acts as a flux. To opacify, zircopax, tin or sometimes titanium dioxide is used. edit: Pres linked a glossary to the top of the Studio Operations and Making Work section, it's a good place to look up materials etc.
  4. Thanks for posting my question Pres. hanging planters for succulents
  5. Sounds like it's just the wax burning off. Is your kiln vent working okay? Welcome to the forum
  6. Best Way To Reglaze

    Some glazes can really run when you refire them or layer two glazes, if in doubt put the pot on a scrap waster piece of bisque so if it does run it won't run onto your kiln shelf.
  7. Looks like there is some plaster film stuck to the clay. I would toss the trimmings that have plaster on them. Glad it worked!
  8. This topic has come up a couple times, link to one of the threads here. I can't recall ever seeing a list of ceramic chemicals that are teratogenic but that would be an area I would check with a medical professional about.
  9. Jerry Bennett workshop handout for making paper clay here, it covers pretty much everything for making paper clay. For the pulp I know a lot of potters use cotton linter rather than paper cellulose. I would be inclined to try it without molochite first. Welcome to the forum
  10. @AscotLady, if you don't like the way it looks now you really don't have anything to loose by refiring to the correct temperature. If it's a large or thick sculpture I would heat the kiln very slowly, especially through the 530 to 600C range.
  11. Since the pots you fired to cone 10 are no longer porous it's going to take a lot of time and patience to glaze them and the task will be more troublesome than its probably worth. Warming the pots up to around 180F will help get the glaze to stick. If the pots are very precious to you it might be worth the effort but otherwise I would chalk this up to a learning experience and start over. Yes you can use your cone 6 glazes on your pots that have been fired to cone 10, they will need to be fired to cone 6. Going forward I would use a cone 6 clay with your cone 6 glazes. Firing to cone 10 in an electric kiln will wear your elements out much faster than going to 6. Welcome to the forum!
  12. If you have a shallow basin wide enough you can dip it horizontally so you won't need as much glaze, a couple inches more than the depth of the plate should do it and wide enough to be able to skim the plate into and out of the basin. Staple removers with the prongs filed down so they will fit on the rim of the plate (or tiles or lids etc) one on each side and skim it through the glaze. The filed down prongs just leave tiny little snake bite type marks that are easy to smooth over. (btw your glaze looks like it needs to be sieved to get those lumps out or mixed up some more before dipping)
  13. Test firing my new kiln

    Are the instructions on pages 3 and 4 of this what you have? With a brand new kiln I would do a very slow first firing to bisque temperatures plus a very long soak at the end, I would also leave the peephole plugs out for the entire firing if you are not using a kiln vent. You can verify temperatures with cones when doing this firing, just do it when the kiln is approaching your target temp / cone. I would also put your cone pack on a waster scrap of clay if you do a very prolonged soak.
  14. It’s always interesting to see what people are working on, a one off pot, a series, pulling handles, working out a new design, glazing, glaze testing.… just a snippet from your day of something in progress. My question would be what’s on your workbench? (pictures would be a welcome bonus!)
  15. Nope, the alumina hydrate will make a crusty mess of the glaze. To glaze something all over ceramic stilts are used to support the item then the little rough spots the stilts leave behind are sanded down after firing. The higher fire you go the higher the chance of slumping / deforming the bracelets.
  16. 2003 Studio Potter magazine had a list of different things to try with shino, it's reprinted here. (41 variations)
  17. Brand new baby Skutt not operating

    If you go to page 23 of this, under the configuration heading there is an Output#4 Option which looks almost like your display code. OPb with part of the b missing???? Long shot but as close as I could find.
  18. Controlling Drippy Glaze

    Another approach would be try a stiffer base glaze in place of your white glaze. The stiffer glaze will act like putting the brakes on to slow down the flow. If it doesn't flow enough you could try the rhubarb alone for the top area of the pot and a stiffer white glaze for the bottom part. I don't use commercial glazes but from the Coyote website one like this would be a stiff glaze. They are recommending it for majolica type work so it shouldn't move.
  19. Faking cone 10 MG2/Soldate at cone 6?

    The subject of manganese comes up frequently, link to a good thread about it here.
  20. Lithium replacement

    I don't think I was presenting an argument for avoiding lithium, I was simply trying to say that without testing an underfired or unbalanced glaze has the potential to leach lithium and without testing we don't know how much nor do we know how much is too much as there isn't even drinking water limits for this material. I use spodumene in several glazes, I don't avoid lithia.
  21. Lithium replacement

    As Gavin Stairs says we are not in the business of supplying mineral supplements. Taken from this very common sense article. "Trace Elements The thing about toxicology is that everything is toxic at some level. Hardly any exceptions. The question is what level? That is, how much? Toxicologists try to establish the 50% mortality level. With something like water, it is inconceivably high (i.e., drowning). With arsenic, small. With cyanide or strychnine, very small. Most of the elements and vitamins have moderately small levels, but some, like vitamin C, are quite large. It's rather hard to poison yourself with vitamin C. Not so hard with iron and vitamin B complex. Monona Rossol wrote about the overlap of the toxic dose and the therapeutic dose of Lithium in Ceramics Monthly. I am oversimplifying, of course. There are synergistic effects which make it highly variable in some cases. The issue with trace elements is that we need some, but not too much. The dose in a multivitamin capsule is calculated to be enough for a daily requirement for a healthy adult, but not enough to be toxic, even if the person taking it has several times the ordinary daily intake from other sources. The issue with pottery leaching is that we are not in the business of mineral supplements, and we cannot give a carefully controlled dose of what leaches from our pots. With some things, like silica, this is not a problem. With others, like cobalt and iron, it is rarely a problem. With things like chrome, vanadium, molybdenum, lithium, barium, perhaps aluminum, and so forth, it may be a problem. With lead and cadmium it definitely is a problem in certain cases. In some of these cases, we don't know if it is a problem or not. The safe situation is to have durable glazes which do not leach significant amounts of anything."
  22. Lithium replacement

    If you are at the maximum target dose prescribed then add supplemental lithium from a leaching mug how much are you getting?
  23. Lithium replacement

    Will someone taking lithium for bipolar disorder get an overdose from an unbalanced or underfired glaze? I don’t think this question has a definitive yes or no answer. My understanding is the toxic and treatment levels of lithium are very close, will lithium from a leaching coffee mug push the person into the toxic area? I don’t know. I’ve always tried to approach the safety issues with the materials we use in a manner that errs on the side of safety and common sense. Educate yourself about the materials you use, firing conditions and maintaining good studio practices while handling, applying and firing. If in doubt do some glaze testing. In regards to the glaze discussed in this thread we also have to take into consideration the firing to cones 06 - 04. According to Dr Carty (glaze guru) from his "Overview of Glaze and Glazing Safety" general rule for glaze safety is to fire to at least cone 1.
  24. What type of clay are you using, lowfire, or mid or high? Also, do you know how vitrified it gets? (absorption figures from the supplier if you haven't run your own test) I'm assuming you are just talking about using slip on the outside of the cups / mugs? BTW it's not a stupid question at all! Welcome to the forum

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