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Everything posted by Min

  1. @tinypieces, video below showing how to's and why's of a damp box. (includes how to mix up the plaster) Wow, and here I thought my wax was expensive! If misting works over underglaze then wonderful, my underglazes (mostly Spectrum) have enough binder in them that misting doesn't soak into the clay very well though.
  2. I can see if there is too much WD40 it could cause problems since it's a water displacement product. I know if I use too much WD40 on molds my porcelain cracks like crazy.
  3. They shouldn't explode Lee. Terracotta is porous so it's easy for any moisture to escape. I'ld put a test piece or even some shards of the same type of pot in a saucer and fire it up to ^04 and see what happens. If the pots are Mexican terracotta they could be made from a really lowfire clay.
  4. What Mark said then put them through a sieve, 80 mesh would be fine. If anything is left in the sieve then add a little water to it and microwave it until hot then put it through the sieve. To get the sediment out of the bottom of the container pour off all the liquid you can then use a loop trimming tool to cut the sediment out. Are these dipping glazes or commercial brushing glazes? Welcome to the forum.
  5. If you don't finish the piece in one session I would use a damp box. (it's just a plastic bin or tote with a tight fitting lid that you pour plaster into. Once the plaster has cured you place your piece(s) in the box and the damp plaster keeps the pot from drying out.) Don't use the plaster too wet or you can get water splitting of the pots. (been there done that) Re the Forbes wax, it's going to depend on how thick and how dry the pieces get while you are working on them. It's not going to hurt to do both inside and out with it, yes it will completely burn off during the bisque. It's expensive for me to order in Forbes, I don't know if it is for you too? You could use Forbes on the underglazed part and a less expensive wax on the non-underglazed part to save some money.
  6. Wax resist will slow down the drying. I like Forbes wax, the oil based ones I find don't dry as well and can be a bit gummy or sticky unless they are left to dry for a fair while which defeats the purpose. I use a size small 3M respirator and find it fits me well.
  7. https://duncanpaintstore.com/og803-mother-of-pearl
  8. @Olinda, are you looking to have the iron colour on a glazed piece or is it for non functional but you want a bit of shine to the iron? If you're looking for something to add to the iron for a non glazed finish you can mix iron oxide with gerstley borate. I've used it up to cone 6 as 50 red iron oxide plus 50 gerstley borate. There is shine to it at this ratio. If you want it less shiny then decrease the gerstley borate, try it with 50 iron and 10 / 20 / 30 gerstley. (don't use the 50:50 version on the bottom of a pot, it's fluxed enough to stick to the kiln shelf)
  9. For anybody looking for a good intro to glazes the terrific book Mastering Cone 6 Glazes by John Hesselberth and Ron Roy is back in print, including colour pages. If you are interested in ceramic glazes, slow cooling, durability and host of other subjects this is a great book to own. Price is reasonable. from Amazon from Echo Point Books and Media (the publishers) from Barnes & Noble
  10. Can you order some in from India? I did a quick Google search, Ravi's manufactures frits, including some boron ones. You could contact them and ask who the distributors are in your area. Also found that Bhoomi Pottery has Gerstley Borate. If you are going to be working at cone 6 I really do think that it would be worth finding a source of boron. A zinc fluxed Bristol glaze is one possibility of avoiding boron but having boron available will open up many more glaze choices.
  11. I'm not seeing anything that contains boron. Is a boron frit, gerstley borate or even ulexite available to you? Boron isn't necessary for high fire but it's really beneficial to get a good melt at cone 6.
  12. @Stone Fig, glass does look gorgeous when fired on clay but there are definite safety concerns with this practice. You mentioned you were looking for a glaze to fire on the inside of a bowl, I'ld really reconsider firing glass on a functional piece. There is a very strong likelihood of getting glaze slivers coming off the melted glass, might not happen straight away but it's a distinct possibility that it will happen sooner or later. This subject has come up several times on the forum, can do a search for other opinions on it, one link below that I started that discusses it.
  13. I buy a drink from the nearest coffee shop and save the cup. When I need to use the washroom I take the cup with me and use the one in the coffee shop. Sometimes they say they are for customers only so I just wave the cup at them when I go in. Those porta potties can get really nasty at a busy market, probably worse for women than men.
  14. @Hannah Greenblott, sounds like maybe you just added too much that wasn't blended in well. At about the 2 minute mark in the video below you can see how little John Britt uses in his deflocculated slip to thicken it back up again.
  15. Linking a video of Eddie Curtis' YouTube video. @JamesGOLDSMITHS24, I'm changing the title of this post to better reflect the content. Welcome to the forum.
  16. If the Shaner clear doesn't pool enough for you when thick then take out some of the epk from the recipe. The more you take out the more likely it is to craze though. edit: If the glaze is "too thick" and the pot is "too thin" then you can run into problems with the glaze layer cracking or even pulling the pot apart where the base meets the wall. How much is too thick and too thin is going to vary but I wouldn't make potato chip thin pots to pool glaze in. @Stone Fig, thank you for giving us an idea of your experience, it's helpful!
  17. The version 5 above is just showing what I would do to lower the calculated coe down from where it is in version 4. You are using glaze calc software right? What I would suggest doing is working on a version of this with an even lower coe then just doing a quick line blend of the original one and one with a super low coe. See where the crazing stops. Yes, there is room for more magnesium in there so play with the talc amount also. BTW spodumene can have detergent reside on it which in turn causes a bit of frothing when the glaze is mixed up. I don't worry about this for glaze testing but for a full glaze batch I weigh out the spodumene then add a fair bit of water to it, swish it around quite aggressively then let it settle and pour out the frothy water.
  18. Hi Tom, That's good the sub v4 didn't craze on the B-Mix test tile, will be good to hear if it works on a test cylinder. Any chance the glaze was just thicker on the inside of those other claybodies than the outside? If a glaze is on the edge of crazing just having it thicker can push it into crazing. Does the clear for the red clay need to be non coloured? Could you use an amber coloured glaze or would mess up slips or underglaze work on them? I don't think I would add much, if any, more boron to the sub v4 glaze. It's topping out at 0.34 as it is. Too much boron can actually induce crazing, plus it can make a glaze "soft". edit: I played with the recipe, got rid of the tiny bit of nepsy that was in it plus reduced the custer, both to reduce the KNaO. Added some spodumene (to supply some lithia) to replace the KnaO I took out. (all 3 being alkali metals so R2O:RO ratio is still in the same range). Silica and alumina levels rebalanced then recipe re-totalled to equal 100. This is just an idea of where I would go to reduce the coe even more if that's the direction you want to take. I like your suggestion of adding a couple % of zirconium, that does help with crazing. (even though the calculated coe will raise slightly)
  19. I think what's going on here is a difference in semantics. When I quoted Orton's blurb on TC's and drift I was reading it as a potter. @Bill Kielb, I believe when you say: "Drift actually is the movement downward whereas normal aging is the movement upward. Both conditions usually apply but drift (downward movement) is often the superior effect." I'm going to assume you are writing this as an electrician. To a non electrician and potter such as myself and those to whom Orton and all the kiln manufacturers are speaking, the term drift does not mean drift is only a downward movement. Potters speak isn't the same as electrician speak in all situations.
  20. I wouldn't leave a kiln firing unattended other than for doing a candling (preheat). What is it about firing that the admin is concerned about? Is the kiln vented? Is it located where children could accidentally come too close to it?
  21. You can find mention of thermocouple (TC) drift with type K TC's on any of the kiln manufactures websites. It is also on the Orton website. From Orton: "Thermocouples All controllers depend on thermocouples placed in the kiln to measure temperature. With time, the output of most thermocouples will change, this is called drift. When drift occurs, the thermocouple no longer measures the same temperature as it did when it was new. Typically, drift causes the kiln temperature to be higher than the temperature displayed by the controller. Type K thermocouples drift more than Type S and these need to be replaced after 50-100 firings, or when damaged. Orton recommends that Type K thermocouples normally not be used at higher temperatures (above 2100°F, unless they are made of 8 gage wire or enclosed in a protective sheath. Smaller diameter (14 gage) wire are not advisable for repeat firings above 2100°F. Type S can be used when firings regularly exceed 2100°F." It's really not a big deal to place a cone pack in the kiln to verify the TC is reading accurately. If it's badly worn then replace it, if not then recalibrate.
  22. Looks like the Wenger company and Mason both started out in Stoke on Trent but I don't think the colour name Victoria Green is proprietary to Mason. I found this little bit below about the name of that colour (from this link). "Origin and History The origin of this pigment is obscure. The potter Sir William Burton introduced the pigment to the Society of Mural Decorator and Painters in Tempera in about 1900. The Society of Tempera Painters named the ceramic pigment Vernalis. Victoria green was the name designating a calcium chromium silicate pigment developed for use in ceramics. The name was also used by artists' paint manufacturers to designate a mixture of 80 parts of Viridian (Pigment Green 18), 40 parts of zinc yellow, and 10 parts of barite, gypsum, lithopone or zinc oxide (Pigment White 4). Victoria green was sometimes called permanent green. The Colour Index lists a green oxalate dye named Victoria green as Basic Green 4 (42000)."
  23. Has anyone else noticed a resurgence of 17th century tulip vases in the past few years? The kind where each stem is held up with an individual tube like holder as part of the overall vase? This is the kind of thing I mean. It seems like everyone is saying no to tulip vases but I'm seeing more of them. Congrats on your first juried Show Liam!
  24. @Splodgeink, as well as the chance of lead as @Hulk pointed out I would be extremely concerned that uranium oxide will probably be in the orange and reds. It's just not worth taking the chance with these, I would suggest handling them as little as possible and getting them disposed of through a toxic waste facility.
  25. @aliceb, one of the things that is repeated all the time with ceramics is "try it and see". There are just too many variables to answer your question with a definite yes or no answer. Try a piece and see how it comes out. Fire your kiln slowly. I haven't come across any manufactured glazes that specifically say they can be used for single firing.
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