Jarman Porcelain

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.

Thank you everyone for all the replies! This is amazing. I've not found people elsewhere this helpful, you folks know your stuff. Kelly! I'm overjoyed to see another bone china piece that seems to have a touch of green in it! I was a little unsure at first, the plate you linked is possibly porcelain, and could be glazed green, but the Narumi piece has a green band around the footring where thick, but a yellow body. I did some digging and I found some 1980s bone china of theirs online with a distinct green tint that matches mine very closely. Super exciting, you must have done some serious googling. I will say green is not common at all, nothing I have that wasn't made by me is green, nor has anyone else's that I've checked. It is clearly out there though. I'm put at ease seeing it in something made professionally, it can't be a sign of fault. It must just be some arcane material interaction. It couldn't be iron, as all other bone china would have iron in similar amounts. My bone china has only slightly less iron on average than vintage English bone china (they entirely use nzk now I'm told), so I'd imagine I'd see similar results if iron were the culprit. That leads me to look at differences, I use Veegum T and don't use Cornish stone or a sub. It must be something in either of those. I've already tested real bone ash vs TCP, both giving greens, so that isn't it. My mind zeros in on the Cornish stone, I can't be sure of much else, but I can be sure that Narumi wouldn't import Cornish stone, they'd find another flux. As they produced ware with that green as far back as the 80's, whatever it is needs to be available back then. That possibly rules out Veegum T, but maybe other refined Smectites were available? As min points out those contain magnesium, that could be it, and is easy to test for! In my work, I've been playing with combinations of frits, soda spars, and silica in the 25% of the recipe that would have been Cornish stone. Min, I will absolutely test your suggestions, but you don't need to ship me any materials. That is too kind, but I share space with a long running large production studio (also where I work), odds are I can dig some vintage stuff up in there and work something out. I'll get the sub on my spring order. For Peter, yes I can confirm I've tested it in many lighting conditions. I use neodymium a bit and have lots of lights to show it off, made that test easy. Thanks everyone, I've got some serious testing to do now. I'll check back frequently!

To give back to the thread, I just had great success adding 4% Veegum T ($$$) and 0.5% CMC gum to my LF clear and then gelled it further with a touch of epsom salts. The result is a bucket with about the worst rheology possible, unworkable by all rights. However, I dipped a couple pots through the glaze, shook them a bit, and got really good even application. It dried well without any cracking. I tested layering and that worked great too! I won't get a chance to fire for a bit, but thickness is good so I can't imagine how it could go wrong from here. Up to you if ease of application is worth the VeeGum T tax.

Oh yes, I've done both actually. The bisque looks normal, a slight pinkish hue, but less pink than my halloysite porcelain. No trace of green. I've looked at cut samples of bisque and vitrified pieces under magnification up to 80x, I can't see anything green.

I have had it fired in different kiln, all the same result. I have occasional access to a gas firing, so I'm going to ask if they can put a test into the next firing for me. It might not shed any light on this, but more data is always good. What do you mean by a low-fired test tile? I've certainly seen it in bisque a lot, but I assume you mean something else.

If this were the case you'd see this in commercial bone china as well. I'm using NZK, Grolleg, Standard Kaolin, Veegum, bone ash, silica, frit 3110, and Neph Sye. Those are all materials used in industry, and are all noted for they exceptionally low iron content. As I said in the other thread, I'm not ruling it out, but it seems extremely unlikely as this oddity is apparently unique to me, but none of my materials are. I'm also sieving the slip, as well as running high powered magnets through it to remove even more iron (something industry also does). My suspicion is some kind of crystalline silicate of calcium is forming, the body becomes very fluid in the kiln, and the body has an absurd abundance of calcium. It could either be green in colour, or blue in colour and then giving green when light passes through those molecules and the yellow we all are used to from oxidation firings. Again though, the problem I'm facing with this explanation is much the same, if I'm getting this, why does it not occur in other's bone china? I plan to make a small batch with distilled water, hopefully this week if possible, that seems like a very worthwhile avenue of exploration.

I'll add in my other image, which compares my bone china to laguna's frost. The quality of the white is totally worth all the hassle.

Happy to, splitting this sounds like a great idea!

I also have been considering this explanation, but this isn't glass, and if this were the case you'd see it in all oxidation fired porcelains. I won't rule it out, but it seems unlikely to me. The green is definitely in the body, not the glaze, as my unglazed bisque (fired to vitrification) gives the effect just as strongly as glazed pieces. Furthermore, if this were the case, commercial bone china would also have this effect. If you can think of a way to test this I'd try it, but I'm also unsure how to test that. I don't think it is possible to produce a control that contains no iron.

https://insight-live.com/insight/share.php?z=7WnpT9vC3b This has some great info on your glaze, as well as multiple revisions meant to solve known issues.

I don't have a good sense of what is causing it. I've mixed hundreds of tests now across many variations on multiple recipes, all produce the green. It isn't Chromium or Copper, neither are in any of the materials I'm using. I can rule out contamination as I first started working on this 7 years ago, but only got it really producing results in the last year. I've been using materials purchased at various points throughout, so the contamination would have to be consistent for years, and also not show up in my production that shares use of these materials. Distilled water is a great test idea, I'll run that test soon. I would think I'd see the green in my porcelain too though if it was my water, unless something in the water reacts with phosphorus. It is one thing that is constant, and the water here is extremely hard. Maybe trace elements of magnesium? Thanks for suggesting this, it isn't something I was considering. I have considered that maybe some weird crystalline silicate of calcium is forming as I cool the kiln. There is so much calcium in the body, and it becomes quite fluid in the kiln, perhaps something green is forming (or blue and then combining with yellow from trace iron/titanium?). I always run a slow cool, but I have some work that doesn't need it. I'll save up enough of that work to run a cone 6 without a slow cool and see if that changes things. Another thought is how trace amounts of iron in reduction give us celadon greens. I'm firing in electric though, but maybe I'm getting some localized reduction? Seems unlikely. I've come to really like the green, so if it isn't a sign I'm doing something wrong I'm going to keep it. I just really want to know why it shows up. Attached is an image comparing my bone china to Laguna's Frost. For those outside North America, Frost is a halloysite porcelain know for burning a nice white (for a NA porcelain). You can really see how the bone china is a cool white, with a distinct green tint even without light being directed through it. As I said before, I find it pleasing.

Do you have photos or a detailed description of what is happening? There isn't enough information here to help you.

I'm using various recipes of my own creation, all closely based on the classic 25:50:25. Notably I'm in North America, so I've been testing subbing soda spars and various frits (mostly 3110) + silica to replace the cornish stone. For Kaolins I've been using NZK, Grolleg, and Standard Kaolin. I've used both TCP and bone ash, the real stuff burns whiter and fluxs much more in my experience. I worry that green is a red flag that I'm doing something wrong, but the ware is very well vitrified and very strong. If it were a common problem I'd imagine I'd be able to find information on it.

I made a body of sculptures out of porcelain paper clay that were somewhat similar. I was using a translucent cone 6 porcelain and firing to cone 8. To prevent them from collapsing in the kiln I made a rudimentary saggar that I placed them into, then filled the void, as well as the piece, with silica sand. This went about half way up the side, I stabilized the "handles" at the top by rolling up some fiber blanket into a tight tube and running through each loop. For more complex shapes you can use kanthal wire to bind rolls to each other. Make the saggar (maybe armature is a better word?) out of cone 10 raku clay or fire clay so you can reuse them forever. Good luck, those pieces look great already.

Hello folks! Curious if people are still checking this thread? I started throwing bone china about a year ago and am getting some decent results. I'm looking for more online resources, as well as colleagues to discuss with. I simply cannot find either of those. Bone China people seem very guarded, it is so nice to see someone helping others in here. I learned the hard way about oil from your fingers being enough to resist glaze. Is it just me, or is glaze fit unpredictable? I've had glazes that craze normally shiver, glazes that craze normally fit well, but also had glazes that fit normal ceramics also fit bone china. There seems to be no rhyme or reason, it strikes me as odd. Edit: Oh, I almost forgot, my bone china glows green! I've googled and searched everywhere, but cannot find any information at all. I've tried with florescent, incandescent, and sunlight, all green. What color does yours glow?