High Bridge Pottery

Looking at those prices and checking how much they sell 3124 it seems something like this could be cheaper. I am worried that the cornish stone has clay added to get the chemistry so not sure my recipe will suspend for very long in the bucket but even with 5kg petalite and 1.5kg 3124 it seems cheaper. Not sure how to add clay without adding too much Silica and Alumina. Might be worth testing if you have the materials already available in the studio.

Why are they so flaky? Is that just part of old fiber lids or has an already bad rigidiser job coming loose? Never seemed to have an issue with my fiber lid.

How are you sourcing lithium? Should need around 500g for a 5 gallon bucket? Neil beat me to it I wonder if you could use a lithium feldspar as a cheaper option and cut out some of the cornish stone? Depends on the KNa chemistry. Had a quick go at the chemistry but you can never get that much lithium in the glaze from a feldspar without loads more silica and alumina. I can get close with this but no idea if it is any cheaper. Potash Feldspar - 22.5 Petalite - 44.5 Whiting - 9 Ferro Frit 3124 - 14.5 Red Iron Oxide - 9.5 Is the RIO/colemanite suspending the glaze or is the cornish stone a mix of feldspar and clay?

Looks like it has forced air and forced oil with a spark plug as far as I can tell from the few pages I am reading about oil burners.

Is there no way to get any money for your kiln? Even if you managed to get 50% that seems like enough for a small pug mill. Such a shame that they are putting up barriers for you instead of trying to help. In the end we are all trying to get to the fired ceramics and whatever way that is done doesn't really matter. I found wedging to be a bit of a showoff game with some people "oh look how much I can wedge at once to get rid of bubbles" I can understand that he likes the consistency one way but why force that onto everybody? The only other idea I have is adding some grog into the clay, that should give it more working strength.

I thought you had already moved but from reading a bit more it seems you are still waiting to move? Hopefully your new location will have a better studio. I wonder if there's problems with the pug mill which is why they mix it up wet. Seems like others are finding it too wet if they are making arches and trying to dry it out. I wish there was a better answer than leaving it out to dry and wedging it. I did wonder if you could dry it enough and get them to send it back through the pug mill. Do they make the clay from scratch or does it arrive this wet from the suppliers or it it when they recycle the clay?

Having a look you can get some quite cheap ultrasonic generators, not sure that's the right terminology. It would be fun to try it but I can imagine turning it on and everything moving around and getting stuck together best to try it first with a cold kiln and see what they do. Not sure how well it will transfer up the shelves and posts as they mostly seems designed for water baths. Thinking about a way to do a reduction bisque. I had brought a propane bunsen burner with the idea of adding some gas into my electric kiln but I wanted to crunch some numbers to see how far I could get on the bunsen burner alone. Saves me taking the kiln outside and degrading the elements. I have 50ish insulating fire bricks sitting around waiting for me to do something with. As far as I can measure the orifice is 0.75mm - 1mm somewhere in between that anyway. I have a 32mb/14.9wc propane regulator which says a max output of 1.5kg/h which seems to equate to 71,250btu/h. Looking at orifice size I can get 7,680btu/h @ 14wc from 0.75mm and 13,900 btu/h from a 1mm orifice and I think it is sized somewhere between there. Olsen says that 10,000 btu/h is a good estimate for every 1 cubic foot of space. Not wanting to spend loads more money I have tried to design an updraft kiln with a 9inch cube internal space, just under 0.5 cubic feet. This will let me build it without too many extra kiln shelves as hopefully the lid bricks will hold themselves together (I may have to add extra as weight to stop them falling into the kiln) and I can use normal bricks to hold the floor together and make enough space under the kiln for the burner. I have considered buying another bunsen burner and having two coming in horizontally at the sides instead of one in the middle underneath the kiln but this is where I am at. Here's a quick design using 32 bricks. Trying to decide if the flame will be fine going in straight and hitting the bottom shelf or if I should try to split the flame so it comes in on a 45.

Would they let you bring your own stoneware clay to the studio?

Very easy to buy leaded glaze and lead bisilicate frit in the UK, harder to find litharge from ceramics suppliers but it is still available through other sources.

Glad you figured it out and happily firing again Always nice to solve a mystery.

As long as the burners have flame sensors on them it will cut off the gas supply if the flames ever go out. I don't think the flame can travel back down the gas pipe due to their being no oxygen to burn with in the pipe.

The issue would be it needs to be wet and put under the glaze when the glaze is molten to produce steam. Sorry it was a bad joke, I am not very good at jokes

Looking at Sue's clear it is in the 7-8:1 Si:Al ratio that I have found to be best. I have certainly come across the idea but it seems very impractical to try and vibrate a kiln ultrasonically. I have also considered how I could add a potato to my glazes as they use that to remove bubbles in glass too. First time I read it I thought it must be a typo but turns out it is a valid technique.

Will soaking the plaster in water reverse the effects of sodium silicate or once it is in the mold it is there for good and you are better off making a new one?

It's a good place to start but I have never been satisfied with the answer to make the glaze thinner. I don't really see it as solving the problem just making it less visible. Not that Sue is claiming it does get rid of bubbles as she explains a thinner application just allows for a lower density of bubbles.

I remember adding an actuator onto the damper but I don't think it was ever controlled by the computer. That was the plan but I don't think the project ever got that far as the damper was fully open until 1000c and then closed a little and left in the same place for the rest of the firing so it wasn't much effort to do that manually when it got to 1000c. In the end the guy got a second hand blaauw kiln which was much more advanced than my bodge job.

Thanks Peter, will either of these dissolve the silica or will that still remain with both the hydrochloric and acetic? One reason I wanted the HCL was because I could also try doing a flame test and see if that gave any clues as to what I have, although lithium and calcium seem close in colour. I am looking to do some lime mortaring of my house this year so it might be worth buying the HCL concrete etcher or brick/mortar cleaner anyway as I am not very good at keeping the bricks clean.

It a tricky one to decide, will the initial cost to get an electric kiln up and running save you money in the long term with lost ware and time you could be doing something else. I have semi automated a gas kiln adding a controllable valve onto the pipe but that is not the easiest thing to do. It just meant instead of turning it up every 20 minutes the computer did that for you. There was no brains really, the first firing I did have to turn it up via the computer and record what was set and run a simple program to repeat that for me the next firings.

That one did look a bit suspect to me because it has a hot bit and a cold bit. Compared to the rest it seem odd.

Thank you for the link, I have not seen those tests before so will have a look through his research. I am still unsure if fining agents will transfer across well to glazes but it is worth testing some out and seeing what happens. The red clay tests are actually Tim's tests and I am pretty sure he was using lead glazes. Never liked working with red clay myself. He is saying it is a body problem but only related to sulphates as the rest of the organics will decompose happily at bisque temperatures, Neither of them bring up any temperatures and I think are just talking in general about the problem across a wide firing range. I am not sure all the sulphates do burn out even at that temperature. There's an interesting picture in the last thread where they measure the gas evolved from the batch containing 1% sodium sulphate and one is reduced by adding 0.2% carbon to the mix. In the oxidised batch they only start going out at 1000c due to some reaction and don't really decompose until over 1400c. I think I did read that sodium sulphate is one of the hardest do decompose. It does make me wonder if I could even get them to decompose in a bisque firing with reduction, especially if I am only going to 800c.

I don't think they are talking about organics in the bisque, most are burnt off pretty easily just the sulphur stays around. I feel it's pretty relevant to getting rid of glaze bubbles the question is do I really have to get rid of bubbles you can only see through a microscope when the glaze layer is thin? Probably not but I want to see if I can. I gave up trying to make money from my own pottery long ago and instead have fun testing and experimenting. I am not even sure how relevant my fritware tests were to any of my work but I enjoyed doing it.

Yes looks like I can source it there, thanks for the tip Callie. Not so sure about pool supplies in the UK Bill I am sure there's commercial suppliers but not many people have their own.

I wonder why it is overriding the firing. hmm The controller seems to be switching on and off the brown wire going to the weird black box and then that is switching the contactor. I wonder if you could just attach that brown wire to the coil instead of the yellow coming from the box as they both seem to be 240v.

The yellow box is a transformer, it will take the 240v from the wall and convert it to a lower voltage. Looks like 24v judging by the sticker.

I have been searching for a bubble free glaze on and off for many years. There's an old thread here - A lot of the time I can't even understand what I am trying to say in my old posts (and I wrote them xD) but if you want some context it might be worth a read. I would like to thank everyone for being so patient with me over the years, slowly stumbling about in the dark trying to understand ceramics. I very much appreciate it For the "Too Long Didn't Read" the old thread tried - Removing as many ingredients with loss on ignition as possible. Glazing an already vitrified clay body. Using holds and drop holds. Changing fluxes, silica and alumina amounts. In the end nothing really seemed to produce satisfactory results except reducing silica in the recipe. There seemed to be a link between silica joining the melt and bubbles being produced. Recently I have found a few more papers on this subject and wanted to share my findings. The first was in Transactions of the American Ceramic Society Volume II, Blisters in Glaze - Stanley G. Burt. https://archive.org/details/transactionsofam02colu/page/138/mode/2up Back then they seem to have a lot more issues with sulphates coming from the fuel but Burt seems to find the same thing with silica kicking out gasses dissolved into the glaze. It seems to be confirming that the more silica you have in a glaze the less dissolved acids/gas it can hold which ends up coming out of solution. After a bit more searching I managed to find the Seger paper in question in The Collected Writing of Hermann Seger Volume II, The Defects of Glazes and Their Causes - IV The Operation of Sulphates in the Glaze. https://archive.org/details/gri_33125001394697/page/582/mode/2up Again he comes to the conclusion that silica is the main offender for producing bubbles. In a previously bubble free glaze remelted onto an already fired body it will take up silica from the body and produce bubbles in the glaze. Back in Burt's paper in the discussion at the end he talks about a few ideas to remedy the problem. One is to have a glaze higher in silica which is the opposite to what I have found. His reasoning seems to be that the glaze would have less action on the body so reducing any silica coming from the body into the melt. His second idea is to fire the bisque in reduction to volatilise the acid removing it from the body before the glaze firing. Seger also seems to find reduction is one remedy to the problem but does it in the glaze firing. The Collected Writing of Hermann Seger Volume II, The Influence of Sulphuric Acid on Glazes and Bodies. https://archive.org/details/gri_33125001394697/page/644/mode/2up Some interesting things to think about, especially trying to do a reduction bisque firing and seeing if that produces any different results in the glaze. I am not sure I agree with Burt that a glaze higher in silica will produce less bubbles but maybe that combined with a reduction firing could produce results. Now I just need come up with some tests and see what happens.