Callie Beller Diesel

I know my customer, and he's a picky gallery owner.  And, I have an exclusive contract with him, so selling it retail is not an option.  My decision is to give the higher-fire a try; and if it doesn't work, give it to one of my relatives, who won't care if it isn't perfect.   Thanks to all of you who responded; you helped me make my decision.

While I’m one of the first people who will usually say it’s a bad idea to sell crazed functional ware, why are concerned about crazing on sculptural work? Sculptures don’t have the same durability demands placed on them as dishes. They might have their own durability demands if they’re outside, but I digress.

I spoke with my supplier last week, and they said that Plainsman has a 4 year supply IF no one hoards it. Mike at Ceramics Canada has said he won’t sell more than a 50 lb bag at a time unless you’ve been making your own clay body with it. 
So please don’t panic buy. Give everyone ample time to reformulate behind the scenes while still using their current stock.

While I’m one of the first people who will usually say it’s a bad idea to sell crazed functional ware, why are concerned about crazing on sculptural work? Sculptures don’t have the same durability demands placed on them as dishes. They might have their own durability demands if they’re outside, but I digress.

This thread is a continuation of this one started by @Mark C. regarding the addition of another K2O feldspar to replace Custer: Vardhman feldspar from India.
Chart comparing Vardhman with other potassium feldspars plus the analysis I received from Vardhman.

 
 
 

Hi and welcome!
Not a silly question at all. The good news is, hot won’t affect materials, but humidity might make a few things like soda ash or dolomite clump. Anything that is prone to this can be dried out on a baking sheet at about 175 F in a kiln or oven if it’s a nuisance. 

Hi and welcome!
Not a silly question at all. The good news is, hot won’t affect materials, but humidity might make a few things like soda ash or dolomite clump. Anything that is prone to this can be dried out on a baking sheet at about 175 F in a kiln or oven if it’s a nuisance. 

Hi and welcome!
Not a silly question at all. The good news is, hot won’t affect materials, but humidity might make a few things like soda ash or dolomite clump. Anything that is prone to this can be dried out on a baking sheet at about 175 F in a kiln or oven if it’s a nuisance. 

Ferric chloride isn’t necessary by any means. I haven’t done a whole lot of pit firing, but I did a couple back in college. You can get some lovely variations with terra sig on its own, especially if you’ve got a light and a dark colour to create contrast with.

I don’t know about other lustres, but gold and white gold are made of those actual materials, and don’t tarnish.
Some raku glazes that contain a lot of copper can be prone to reoxidizing over time. Usually folks will coat pieces like that with spray varnish or similar. I think it could work for Palladium. 

I don’t know about other lustres, but gold and white gold are made of those actual materials, and don’t tarnish.
Some raku glazes that contain a lot of copper can be prone to reoxidizing over time. Usually folks will coat pieces like that with spray varnish or similar. I think it could work for Palladium. 

I don’t know about other lustres, but gold and white gold are made of those actual materials, and don’t tarnish.
Some raku glazes that contain a lot of copper can be prone to reoxidizing over time. Usually folks will coat pieces like that with spray varnish or similar. I think it could work for Palladium. 

Many commercial underglazes just don't hold up at cone 10. They start to flux out and that causes them to behave poorly when you put a glaze over them. If you're just looking for black or blue, you'd probably be better off making your own underglaze or slip. If you do want to use commercial underglazes, each color will need to be tested to see how it holds up and cone 10 and with your clear glaze.

I'd go with the 325 unless it's really expensive compared to the other. The finer it is the easier it will enter the melt.

I wouldn't get your hopes up on that. We don't get iron staining from our water, and the iron impurities in my kaolins are guaranteed to be significantly higher than whatever might be in my water. Public testing results are under 0.03mg/l, so only trace amounts. We also know for a certainty that iron gives a yellow discolouration in oxidation whiteware bodies. There's a solid chance it is caused by something in my water, but I don't think iron makes sense as we'd see this in all bone china worldwide.

Creeped your insta, my god your slip looks delicious, only way to describe it haha! That pink slip just looks amazing, luminous.

@AndreaK, lowfire and earthenware clay has been used for centuries around the world for domestic ware. How durable this particular  body is would have to be tested, I know some of the lowfire talc bodies were very weak. In North America  many potters have gravitated to midrange for various reasons, one of which is it's possible to have wares that don't leak or overheat in the microwave even if the glaze has crazing or pinholes and it's fine to leave the bottom of the pots unglazed. For lowfire (including earthenware for this conversation) in order for the ware to not weep / leak when used for mugs etc it is necessary to completely glaze the pot. (I do know someone who uses terra sig on the foot but that's another topic). A huge advantage of using lowfire / earthenware is the energy savings when glaze firing and the wear and tear on the kiln elements etc. 
Plainsman supplies really thorough info on all their claybodies. For Snow the link to it is here, click on each of the subjects and it will expand to give the details. For Snow the absorption figures are below. You can see that it has a huge absorption of 28% when fired anywhere from  cone 06 all the way to cone 2. You can also see that the absorption doesn't drop below 12% even when fired to cone 6. What this means is there is never going to be enough fluxing of the clay to vitrify it enough to be leak proof without a glaze. 
Functional ware made from this clay will need to be stilted when glaze fired. From the Snow page (linked above) it looks like Spectrum 700 glaze fits this body well with Snow being bisque fired to cone 04 and glaze fired to 05.

 

Hi and welcome!
It is possible to get durable ware at earthenware, midfire and high fire temperatures, but there are different considerations at each of those points. I won’t use the term food safe, because it’s a bit of a misnomer, and legally only covers whether or not the glaze has cadmium or lead in it. When we talk about glaze durability, we want to make sure that the clay is fired to a point where it would have less than 1% absorbion, the glaze doesn’t leach anything, isn’t crazed, resists both scratching and cutlery marking, and is easy to clean. 
With earthenware in particular, you have to be mindful of glaze fit, because earthenware clay remains porous when fired to maturity, and many will glaze the piece all over, and use kiln stilts instead of leaving a bare foot. You have to be extra mindful of your glaze chemistry, because the low temperatures tend to mean the fun, pretty glazes can sometimes be prone to scratching because they’re lower in silica and alumina.

Hi and welcome!
It is possible to get durable ware at earthenware, midfire and high fire temperatures, but there are different considerations at each of those points. I won’t use the term food safe, because it’s a bit of a misnomer, and legally only covers whether or not the glaze has cadmium or lead in it. When we talk about glaze durability, we want to make sure that the clay is fired to a point where it would have less than 1% absorbion, the glaze doesn’t leach anything, isn’t crazed, resists both scratching and cutlery marking, and is easy to clean. 
With earthenware in particular, you have to be mindful of glaze fit, because earthenware clay remains porous when fired to maturity, and many will glaze the piece all over, and use kiln stilts instead of leaving a bare foot. You have to be extra mindful of your glaze chemistry, because the low temperatures tend to mean the fun, pretty glazes can sometimes be prone to scratching because they’re lower in silica and alumina.

Ferric chloride isn’t necessary by any means. I haven’t done a whole lot of pit firing, but I did a couple back in college. You can get some lovely variations with terra sig on its own, especially if you’ve got a light and a dark colour to create contrast with.

Probably. 
Part of the fun of working with found materials is the variability. Sometimes close enough is all that’s needed.

Probably. 
Part of the fun of working with found materials is the variability. Sometimes close enough is all that’s needed.

Probably. 
Part of the fun of working with found materials is the variability. Sometimes close enough is all that’s needed.

I'm voting iron as well. I think that also accounts for the pinkish tint in low fire bisque pieces. If we were able to have a slab that thick of our clear glazes we would also see it to varying degrees. Window glass is also green for that reason. It look pretty darn clear when we look through it, but if you put some paint on it you'll see just how much color it really has. They make super clear glass, of course, but it's expensive. If I remember correctly they call it Water White glass. Standard  plate glass and such is quite green. I worked for a glass shop for a few years after grad school, and we would occasionally have to replace opaque colored glass panels on buildings that were no longer available from the original supplier, so we just had to paint the backsides. Getting an accurate color match was nearly impossible due to the tinting effect of the green. You couldn't just have the paint color matched to the old panel.

I use a talisman at work, and while it’s great for 10 gallon batches of glaze, it would be wildly impractical in my home studio. The cleanup of the brushes is a pain. 
I have a smaller sieve that sits in a 5 gallon pail at home, and I use a large round sash brush to push the glaze through. It works pretty fast and cleans up very easily. 

I use a talisman at work, and while it’s great for 10 gallon batches of glaze, it would be wildly impractical in my home studio. The cleanup of the brushes is a pain. 
I have a smaller sieve that sits in a 5 gallon pail at home, and I use a large round sash brush to push the glaze through. It works pretty fast and cleans up very easily.