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Min
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Posts posted by Min
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What does your KNaO normally run at in your other glazes?
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I will sit and watch anybody who throws well but my sit and drool person was Robin Hopper.
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Is your work for functional work with the green on the surface that comes in contact with food or drink? Is it important to be translucent?
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This one? If so then maybe Clay Art Center in New York would share the recipe?
(I'm running out of image storage so will delete the image in a short while)
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Hi and welcome to the forum!
Hopefully the cost of lithium products will be coming down sooner rather than later. The Sayona mine in Quebec Canada is set to reopen fairly soon. Also with the extraction method that uses ponds to evaporate seawater for it's lithia content there is also talk of using water from Turkey (I think) that has been found that has a higher concentration of lithia than is the norm so that should help too. When the Canadian spod no longer was available 20 odd years ago there was a lot of outcry that shino glazes were not working as well with the Australian spod. I think that came down to the Canadian spod had a tiny bit of iron in it.
42 minutes ago, Orbit said:I don’t know how easy or possible it will be to adjust the silica and alumina levels with those recipes to allow me to use petalite instead of lithium carb, which I only have about a lb left. And I’m not even sure petalite forms a eutectic with those ingredients at the about cone 06 I do my raku, so that it will melt into the glazes.
The combo of sodium plus potassium aids in the melting of the lithia, I would be looking at those also.
With the petalite version recipe how much is the silica too high? (since gram for gram it is lower in lithia)
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Bracker's Good Earth Clays in Kansas is offering grants to local schools. Last year grants were available nationwide in the US, this year they are focusing on local school art programs. "We service most of Kansas & Nebraska, about half of Missouri, Iowa, Oklahoma and Arkansas, and a bit of Illinois." from the link below, maybe somebody here could befit their school art program. (I am not affiliated in any way with Bracker's, I just get their emails which is where I saw this)
https://us10.campaign-archive.com/?u=ff0b391198e5566d2026a0bfe&id=5ff6d9e137
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I don’t know Rae, think your bad experience isn’t something you messed up on. You are too nice a person to anticipate someone being so nasty. The rest of us, yeah, we messed up!
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Different types of plaster are available for ceramics. General purpose good quality plaster for throwing on and making wedging tables or drying surfaces is called #1 Pottery Plaster. Some people prefer to make throwing batts from Hydrostone which is a stronger plaster than #1 Pottery Plaster but it doesn't dry out clay as quickly.
Whatever you use make sure you use the correct amount of water, it's important to the strength of the finished plaster.
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Didn't calibrate a kiln with a new set of TC's. Kiln overfired by about 3 cones. Entire load had to be tossed and shelves ground.
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Another thing you could do is see if your claybodies are available dry. If they are then after slurry mixing the slops with the reconstituted scrap pug it together with some dry clay to get the right consistency. Even sprinkling the slurry with the dry body would help, it also helps return the body to closer to original state if it's missing fines.
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@CharliesMomma, since you now know what was used another option would be to purchase another kit and make some test pieces with it.(just use something from around your house to make some little pieces with creases, maybe wrap them with saran wrap to get the creases) Wrap them up and leave them in tissue and see if they develop the same discolouration. If they do then finish drying them in the same way as your original pieces. Test those pieces with a quality plaster mildew/mold remover and leave them alone for as long as possible ( a year at least) then check for deterioration of those pieces. I would also contact a plaster restoration company if there is one near you and ask them about this, have them test the sample pieces.
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Hi Maria and welcome to the forum!
Is this the Turner's White recipe you used? If it is did you include the zirconium opacifier both in the past and with this current batch?
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My heart breaks for you, I am so very sorry for your loss. Words are not enough.
Like Lee says it's super important to find out what was used. I would ask the facility if it was a plaster used in an alginate mold. If this is the case there should be a way to remove the mildew. Before doing it I would practice on a separate piece of plaster, not on these treasures. Perhaps the facility could give you a sample or something to try possible solutions on?
@Jeff Longtin, thoughts?
- Rae Reich and CharliesMomma
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Re wax resist, the type you use overtop of another glaze makes a big difference in how it behaves.
Both oil based and water based wax resist will work but the water based one is much more time and moisture sensitive than the oil based one. If you use a water based wax resist overtop of glaze it can curl up and loosen it's hold on the base glaze. The longer you leave it before glazing over the worse it is.
With wax based resist this issue is avoided.
Some resist labels don't tell you if they are oil based or not though, you can tell by how the resist washes out of brushes. If the brushes stay a bit gummy when washed with hot water then it's oil based. If the brushes easily wash clean then it's water based.
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2 hours ago, GEP said:
I am heavy sighing over Gerstley as well. When I did my last supply run this spring, I bought myself about 3 years supply of it. So the clock is ticking, I have 3 years to reformulate my glossy glazes. I also bought some 3124, and I have some 3134 on hand already. Time to start testing. I’m encouraged to hear that others have already found their way through this.
I'm going to make a big guess here, thinking your liner glaze has a fair bit of gerstley in it, like more than 10-15%? If so then your best sub is probably Gillespie borate. In Canada this is running at around $125/50 lbs so it's likely be less than that where you are.
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Quick Google search turns up Glacial Silt is also called Glacial Flour or Rock Flour which is made from tiny clay sized particles of very finely ground particles of rock. Particles of the Glacial Silt/flour can be so small that will suspend in water, this is what makes some glacial lakes look such a beautiful shade of turquoise. Makes sense that it is loaded with silica. Nothing at all like rock salt which is well, salt.
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Good to have the correct info re GB.
If the EPK supply does turn into an issue a really good sub would be to use Pioneer Kaolin in place of it. Chem is really close, only thing to really be of note is the titanium is higher, EPK is 0.01 (in unity formula) vs Pioneer at 0.05. It's from Georgia so supply should be okay unless of course it's a rainy night.
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I originally stumbled across this forum while doing a Google search. I noticed fairly early on that when I did a Google search this forum came up quite frequently; often with multiple threads on the topic. I use the search function here less frequently now given it only searches threads that have been active for the past two years.
Don't know if this is an issue for others here?
- Kelly in AK, shawnhar, Pyewackette and 2 others
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Hi and welcome to the forum!
There are many claybodies that use manganese dioxide, granular manganese dioxide or materials like umber (which contain manganese). Main concern with using manganese oxide in claybodies, slips or glazes, are the fumes that come from the kiln firing. This is a real hazard with manganese! Make sure your kiln is either outdoors or really well vented if indoors.
Manganese oxide is not soluble in water therefore has no bio-availabilty through skin nor can it dissolve in the blood stream nor gut. Again, make sure your kiln is either outside or is really well vented if indoors. (can’t say this too many times)
Glazes should always be durable for tableware, regardless whether the claybody contains manganese oxide or not.
What the manganese addition might do is flux the slip a bit more. I'ld also watch out for bloating if fired past cone 6, maybe only cone 5.
- Mashastein and Rae Reich
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For sure not everywhere has sold out of their existing supplies of GB but the speculation is the California mine blended stock that came after the mine shut down 23 years ago is now finished.
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When I've used Murphy's soap I used a quite damp sponge and applied on a thin layer. I let that dry then repeat with a bit of light buffing between coats. Keep adding coats until water beads off the surface. I then bought some mold soap, for me it works better. (I used Murphy's on a whole fish once, as the plaster heated up it made a nasty smell of hot stinky fish combined with Murphy's, Can't use the stuff now without gagging a bit, probably too much info)
- High Bridge Pottery, Hulk, Chilly and 1 other
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Talc shortage? New Talc - Cim Talc and Fabi Talc
in Clay and Glaze Chemistry
Posted
If the new clay has been tested and is suitable for your tiles then I would be looking at adding either a small amount of a ceramic stain to the glaze or some copper carbonate. There are pro's and con's to both additions.
I looked up the SDS (safety data sheet) for this glaze and it doesn't give any hints on which is used.
Copper carb is prone to high amounts of gassing off which could leave pinholes or micro-bubbles in your glaze. I don't know how fluid your glaze is so this might or might not be an issue. If copper carb does induce this problem a change in firing schedule could alleviate it.
A ceramic stain, probably from Mason Stains, is my other thought on what was used for the green colour in the glaze. Have a look at the Mason colour chart, find a stain you think is closest and purchase the smallest amount you can and try that.
Is your glaze is in liquid form when you purchase it? If so then you need some way of measuring the dry glaze. There are a couple ways to do this but the fastest is probably to weigh out some liquid glaze then dry it out then reweigh it. When you know X volume of wet glaze equals Y weight of dry glaze try the copper carb at 1% and/or a stain at 1%. Fire those and then tinker with the amounts to fine tune the colour. (run the glaze through a 80 mesh sieve after adding the extra colourant)
If you purchase your glaze dry then easy peasy just add the extra colourant to a small test amount and try that.