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Commercial glaze makers have tuned in to the cone 6 market very well in the past twenty years. You can be assured the claims they make hold true most of the time. I’m impressed to see color charts and samples fired to cone 6 of products originally marketed as low fire. The formulas are proprietary so there’s no way to know if or how they’ve changed them to accommodate the higher temperatures. They “just work.” Cone 10 is different. In fact, they don’t make many claims about that, other than “it might work.” This kind of firing usually happens in a gas kiln and a reduction atmosphere. Cone 10 firing in an electric kiln is unusual. The atmosphere makes a difference. Finding a different clear glaze may be a worthwhile chore. Another avenue to pursue is using slip. The easiest course is to use your clay body and add a significant amount of black Mason stain (6600 is my go to). Unfortunately, I can’t suggest a percentage because I haven’t personally fired those test tiles yet (Coincidentally, they’re slated for Saturday, 20% 6600, 80% B-mix5. It’s in a soda firing at cone 6, rather different from what you’re experiencing, but I’m still shooting for clean blackness like you. I’ll let you know), fortunately, you shouldn’t have to worry about fit issues because the slip is mostly the clay body, unfortunately, you’ll have to apply it in a wet or leather hard state to be safe, fortunately, you’re doing sgraffito which suggests you’re already doing that, unfortunately, you’d have to mix up the stuff yourself, fortunately if your current clear glaze works with the clay body it should work with a slip made mostly from the clay body, unfortunately, maybe those bubbles were there already and you didn’t see them until they were over a large black surface and it is just the glaze… Fortunately or unfortunately, this is ceramics. It only gets better.

True artist. Brava!!! Brava!!! It’s a special place we have here. Thank you for the saga. Inspiring.

Build it on a shelf. I think that’s a great idea. Taking rings off the Skutt is a solution to the next problem, you’re thinking it through (You really need a car kiln or front loader for this!). Wheeled carts are brilliant. I struggle with this next bit, because I would rather do things on my own and screw them up (It’s a blessing and a curse) than have either help or an audience. This is a large piece. Having another pair of trusted eyes and hands is indispensable, enlist help for the critical move if you haven’t already considered it.

Don’t fire on drywall it will smolder and burn once calcined. Used to be type X 5/8” - approx. 60 minutes, 120 minutes to sustain a flame. I like the shelf idea and unless once firing, you can grog / silica the shelf after bisque. Many of our large format sculptors would build on a very straight shelf on top of a four wheeled cart.

Hi, I'm planning to make a sculpture that is about 29 inches high and 15 inches wide, it will be wheel thrown so imagine a tall cylinder... it has a really delicate heavy texture on the exterior of the piece so I am wondering what I should build on so that when I move it to the kiln I wont need to actually grab it with my hands and risk messing the texture up. I will be firing in an skutt electric that I can disassemble. A few thoughts - I have heard of people firing on drywall, is this ok for the elements? What about just building on top of a kiln shelf? I plan on putting sand underneath what I build. Any advice would be appreciated. Thank you!

Been a while since I posted about this piece. I have been really busy with so many other things. BUT I did get a rubber master cast made of my medallion. I made it using platinum silicone I managed to get on super sale at a much lower price per gallon than usual. Which is good because I needed a few gallons for my projects though the shore hardness wasn't quite as high as I usually use and that has caused me some issues with the Porthos mold reproduction. Anyway, it's not being an issue with the small medallions I am reproducing. Here is the Cob medallion's rubber master and the first production plaster poured. Once I've cleaned it up and it's cured, the plaster is ready to use if I want to pour open mold porcelain pieces or I can make a mold back with pour hold for a little thicker pieces, or pieces with backgrounds if I want to go back and carve into the plaster while it's still soft. So many possibilities! Anyway, this is the time for me to go back in and redetail anything I want to touch up in my plaster while it's still soft and hasn't fully cured and hardened up fully yet. But one of the things I am going to do is clean my rubber masters very well, then box them up again and pour ANOTHER layer of platinum silicone over top, to produce a negative. Once that sets up I'll have a food safe rubber mold I can use for ... *drum roll please* ... casting CHOCOLATES! OK, maybe I'm just a little bit of a nut. But why restrict my mold making for only ceramics? What fun to do your own designs, your own molds for ceramics, /and/ get to eat your cake too! So, I can hardly wait to see this boy cast in white and dark chocolate just for fun! I'll be giving away some of the porcelain medallions at up coming shows as awards this summer but why not /also/ give away some chocolate medallions for awards too?! Hahahaha! Maybe I get a little carried away.

So beautiful! I really admire the way you approach problem-solving - experience and experiment. It’s wonderful to get new information about the many things clay can do

Thank you all for the wonderful replies! I wasn’t expecting anyone to even notice my post, let alone to get so much help right away. Mark and Jeff, your suggestions will be explored thoroughly. I’m only 23, married 7 months ago, trying to make a living in a field that hasn’t gotten much traction in my area, but if that says anything, i’m happy with a good challenge, I just needed a place to start — thanks for all the support!

To wrap up my little saga on this first ceramic Porthos - he successfully sold at auction yesterday for more than $1600 and I am quite pleased. Yay! Alas, I am having issues with his mold so there will be no more of this edition forthcoming until I resolve those issues or make an entirely new set of plaster mold pieces. I master molded the original plaster mold pieces using silicone but I ended up using a shore hardness 1 step softer (30A instead of 40) and I'm having problems with the new plasters being warped and NOT fitting back together correctly. Even though the silicone rubber pieces are each in their own mold boxes around the sides (but not the bottoms). Grr. I should have known better! Moral of that story is do NOT be lured by being able to get two gallons of platinum silicone for half the usual price on sale when they are not the correct shore hardness I need. Close, but no cigar. Ah well, maybe I can fix the issue by making simple plaster jacket molds for the bottoms of silicone molds so they can't possibly warp from the weight/pressures of the wet plaster filling them. I think there is a very slight gap there that's sagging so it may end up being an easy fix. Maybe. I'll just have to try it today and see. Meanwhile I have already printed a replacement Porthos of the same size and version to make a new mold from. I made the first mold set to cast him in pieces for testing my bone china slip I'm making from scratch here in studio but I also want to be able to cast him as close to whole as possible for earthenware production anyway, so back to the drawing board with claying up... I'm also working on molding him in a larger version so I may well have the big boy casting before I have this smaller version back into production. One never knows! Murphy's Law always rules whether I like it or not.

Cone 06 glaze for your clay will mean it will be quite porous ware. Can you get a majolica glaze recipe maturing at C 1?

I do not have a preferred store purchased overglaze. I spent a whole summer trying to resolve this for our cone 6 glazes so our artists could paint freely with most underglazes. The solution was to modify a clear with a bit more boron to more completely melt. If this is your issue then testing other commercial. over glazes as well as lighter coats of underglaze are probably your best bet. I have never noticed a difference between clays but only anecdotally tested on the variety of studio clays used at the time. Color, thickness applied and even underglaze supplier had the greatest effect - all reasonably resolved with a slightly lower melting temperature of the modified clear. Not all under glazes will go to cone 10 as well with significant color change often being the effect of higher temperature. All our artists, especially sculpture test their underglazed for color. It was not uncommon for a sculpture artist to say, I need to stop at cone 2 - no higher as the perfect color of a full sized human bust that took them a month to make might change from what they wanted. A bit tedious, but an example of all tested in advance.

Not wanting to veer off topic, but I tried, and settled on, kyanite as the groggy/temper portion of my stovetop earthenware clay body (It’s for personal use man, don’t hassle me!). I agree, it’s something special, worth a look. I can’t say anything about the color response, as I was using red clay. I see Tony Hansen has made a low shrinkage bisque patch recipe using just that and sodium silicate: https://digitalfire.com/picture/SpqnhMR7kv

In the UK the declared mains voltage has been 230v single phase I believe. North America uses 240v but split between 2 phases ends up at two 120v circuits to neutral. I think it would be odd to have 120v available without your very own step down transformer. Check before buying for sure to be safe. Check a light bulb or two - ought to be rated at 230v in the UK.

kyanite is something I use in my home made ITC mix and comes in many mesh sizes. Does not shrink The crystals are long and its one of the strengtening things say in mulite kiln shelves It great stuff

My hoarding has paid off in spades so far. Out of Kingman feldspar after burning thru 3,000#s in 40 years now I'm using custar instead but have 1,000#s

Custar is back now Dick at least from Laguna locations

I bet they made some small hobby doll kilns and the like in the UK that ran on 120 like they did here

This is several solutions all in one from Jeff who I had the pleasure of meeting a few weeks ago. Dealing direct with the manufacture on seconds or even a pile of used ones is really a lead worth exploring . I know of several huge piles of them in my area from tow sources as most potters are long gone and the hoarders (I only have a small pile) do not know how to get rid of them here now. Rent a heavy duty truck and go pick them up in MO or have them trucked to you from the factory. I have moved more hard brick in my life than I will ever need. I built several kilns with them ,my salt being the last.

I could have mailed those 4 #3 bricks to you from my hoarder fire brick pile.

Ttwo years ago I rebuilt a 4ft x 4 ft catenary arch kiln that I had saved in a pile of bricks for several decades. While rebuilding it i found I was short 4 #3 arch bricks. I bought a bag of refractory cement, rated at 3000 degrees F, made a form using an available brick and cast them. I have also recently made some bricks using wild clay from my back yard.

Might benefit from a small addition of gum arabic. It's rather fragile and the binder might be helpful.

The OP shows a location in the UK and price limits in pounds. The standard electric service there is 230V. In the US, standard residential electric service is 120/240V, where the normal household receptacle is 120V and other special purpose receptacles are 240V. Thus, in the US, there are a variety of kilns designed for either 120V or 240V service. I don't think there will be any 120V kilns in the UK, but I could be wrong.

If you calcine alumina hydrate to drive off the H2O you will be left with alumina oxide. (approx 35% LOI from it) Whether or not the mesh size is different I don't know. I found a pdf with mesh size of various aluminas here if you want to compare it to your alumina hydrate. If you don't calcine it there might be issues with both the glaze lay down and/or gassing off (plus the obvious difference of adjusting the recipe to allow for the LOI if you don't calcine it).

Only very small kilns will run on 120V service. Any kiln of functional size will need 220/240 volts. The smallest kiln I would consider is an 18" wide model. But ideally a 23" wide model would be the most functional, as you can fit plates and serving bowls in it much easier. First thing to do is to take a look at the web sites of some kiln manufacturers in your area to get an idea of what's out there, and see what the electrical requirements are for the size of kiln you want. Then have an electrician check out your system to see what size circuit your system can handle. Minimum you'll need a 30 amp breaker, on up to 50 or 60 amps depending on the size of kiln you want. At £800 you'll have to buy used, but looking at the new ones will give you an idea of what you'll need to do as far as hooking it up. If the kiln is indoors, it will need to be vented, or at the very least have 2 windows that can create a cross draft with fans.

The stories of jack pots of bricks from busted factories are turning into myth but we gotta keep trying. I'll admit to getting a bit jealous of the stuff I've missed out on but I try to mind my own business, for the most part. The one thing I can try to add is the option to build with castable mixes although cheap alumimna is, again, a thing of the past. From what I can gather one of the most important part of success with castable refractory for salt and soda kilns is the wash. But this will only keep the degradation at bay for so long. Ruthanne Tudball and Jack Troy published recipes for refractory mixes for salt and soda kilns. iirc they might be the same recipes though. Rhodes also mentioned something about brick degradation and density that would be worthwhile to consiedr if trying to modify or improve on a mix. I convinced myself it was possible to find a way forward without actually having any bricks. I let the idea go after finding a precious seed hoard of super duty brick a few years ago but castable refractories would have scratched the itch for me. I'm still tempted to finalise a recipe and design but it's tough to just take something on for fun without a certain amount of spare time and disposable income. For now it's just a very interesting, very part time, research project.