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Min
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Posts posted by Min
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It’s okay to post a recipe.
edit: I asked about recipes and copyright when I started as a mod, was told by admin recipes are considered as a list of materials therefore doesn’t break copyright to post them. -
I use one of these parabolic heaters, (I have 2 but only need to use 1). It doesn't heat the entire room up but heats me up, I just point it towards where I'm working.
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Whichever one you get I’m sure it will be a huge time saver. I would be looking at the ones that can mix as well as vacuum pug, this way you can blend up all the scrap clay from bone dry to wet plus throw in some throwing slop (if your students throw as well as handbuild) churn it up then pug it.
I have a Bailey stainless that I’m very happy with.
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I don't think it's necessary to add anything.
To make a glaze runnier one either decreases silica + alumina or increases the fluxes. To do the opposite, that is make a glaze stiffer, you do the inverse; either increase the silica + alumina or decrease the fluxes.
Looking at the data for Gillespie Borate we can see that it has some silica (just under 12%) + very little alumina (under 2%) the rest of the oxides are boron + fluxes. Now look at the total Gerstley Borate you will be replacing, lets just for an example say a glaze has a rather high 30% Gerstley. If you reduce the substituted Gillespie by 5% that would be 1.5 grams less. Now look at the amount of silica, this would be 12% of 1.5 grams for a grand total of 0.18 grams less silica per 100 grams of base. This is negligible.
If you find a 5% reduction in the amount of Gillespie isn't enough to control the runniness then reduce it further. Do the math to see if you need to top up the silica. Chances are it won't be necessary unless your glaze has exorbitantly high levels of Gerstley you are replacing.
Gillespie Borate analysis from Digitalfire below.
Oxide Analysis Formula SiO2 11.80% 0.34 B2O3 24.50% 0.62 Al2O3 1.70% 0.03 SrO 0.45% 0.01 Na2O 3.77% 0.11 MgO 3.90% 0.17 CaO 23.00% 0.72 LOI 30.90% n/a Oxide Weight 120.86 Formula Weight 174.90 -
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7 hours ago, nellhazinski said:
does the addition of bentonite lower the COE of the glaze?
Not to any appreciable amount in the typical amounts used. Post your celadon recipe, someone might have thoughts on how to fix the crazing. (also which claybody you are using it on)
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4 hours ago, Kelly in AK said:
Next I will somehow run out of space. Haha!
100%!!!
So much stuff, so little space. It’s storing pots for future sales that I have the biggest issue with.
- Rae Reich, Kelly in AK and Pres
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I recall an issue about 15 years ago that some friends had with clay from CAC, turned out it was from the water used in the clay production. Maybe it's this again?
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Hi Kelsey and welcome to the forum!
I'ld ask the clay manager at Tacoma Clay Art Center about this. I'll pm you her email address, she might be able to help. Let us know if she can explain it, it's interesting.
- Roberta12 and Kelsey Sowell
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There are cadmium inclusion stains available in greens. Here is one example from NZ.
https://macsmud.co.nz/products/meadow-green-stain
There are also praesidium vanadium greens, more of a chartreuse colour.
https://macsmud.co.nz/products/lime-green-stain -
On 8/31/2023 at 8:34 AM, ronfire said:
What plaster would you recommend?
#1Pottery Plaster.
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2 hours ago, Bam2015 said:
And she glazes the bottoms! Must use stilts?
Might just be the underglaze or slip with no glaze on the outside and underside of the pots.
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Hi Allan and welcome to the forum!
In a perfect world a low expansion clay with well fitting glazes would be the way to go. In reality many people make ovenware from other bodies, the design of the pot also comes into play as does how to use (and not use) ovenware. There are quite a few threads discussing this, one of them here. I would suggest asking your local ceramic supply place which claybody they recommend.
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1 hour ago, PeterH said:
Textured clay, black , colour, sand down bumps leaving white?
Found the image below on her book of faces page. Maybe u.g. on the slipcast textured blanks then wiped, sanded or scraped down?
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The linked video doesn't seem to work as video for me, it's just a few images that don't show the process of the image above. Brough was asked in a few posts how she does it but didn't answer. Doesn't look like a subtractive process. Perhaps slip trailing done on paper then pressed against the inside of the mold then the white porcelain poured in? Just a guess. I'm sure she spent a lot of work to achieve success with her process.
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Just to add another thing, I wouldn't put the platters/plates on the very top or bottom shelves, temps are more even in the middle section of kilns.
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Hi Marie and welcome to the forum!
It is possible to gently dab on a thin coat of brushing glaze with a sponge onto unfired underglazes then once that has dried apply subsequent coats with a brush but you do run the risk of smudging the underglaze. The other reason it's a good idea to bisque fire the underglaze on is underglazes contain binders that can inhibit the glaze absorption, by bisque firing it prior to glazing the binders are burned off. I have found some underglazes actually have enough flux in them to start glossing over at cone 04 so if you haven't used these underglazes and glaze together before I would do some test tiles to see how compatible they are.
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Hi Naomi and welcome to the forum!
There are quite a few variables that will come into play here. We don't know what is in the clear gloss glaze nor how fluid it is. Does the manganese wash just contain manganese or are there other materials in it? Which oxides would be applied under/over it? Just like with glaze testing it would be best to do some test tiles and see what interactions occur.
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@Tbeans, have you tested the clay and found it is short?
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After having a colossal waste of both time and money trying clay from a couple different manufacturers this year (that I haven't used much before) and getting crap clay that included bits of metal in one line and contaminated materials in another I went back to my original supplier and my tried and true smooth white(ish) clay. First and foremost is having trust in the quality control of the clay supply I use. Tony Hansen is the clay tech for Plainsman, I have used their clays for many years and happily went back to using it after this brief foray into other suppliers, can't afford this frustration again. Second I want a claybody that has an absorption of under 1.5% for the majority of my functional work. (I check the absorption figures myself every 6 months or so) It's a plus if the clay is nice and soft when I purchase it so I try not to buy it if the suppliers stock is running low and it's older inventory they have on hand.
Glaze chemicals got wet. Help?
in Clay and Glaze Chemistry
Posted
Hi and welcome to the forum!
You will want to thoroughly let them dry out as the added water will throw off the weights when you use them in recipes. Is there somewhere outside that is under cover you can open up the bins and leave them to dry?