Bill Kielb

If you absolutely do not find a spec, I would consider trying hypoid general purpose gear oil, likely in the 90w range and observe the heating in early operation. I would hope there are no significant swarf to speak of from machining operations and he was concerned about break in.

I think hard to generalize and no way to guarantee anything is craze free forever. I do think there is reasonable correlation though. Differences in the expansion rate of clay and glaze being the prime issue, followed by the long term reliance of the glaze to tolerate the slight inevitable difference. The fired COE is often a result of fully firing so a clay body or glaze not fired or fully melted may have a different COE than one that is. Just imagine a clay body or glaze under fired by two or thee cones, we would normally expect it to behave very differently than fully fired stuff because it is under fired. If both are under fired the same amount will their under developed COE somehow be even between them? While I think in the ranges you are working in, likely a decent indication, just firing hotter does not necessarily mean the glaze will have greater flexibility and could actually become harder and more prone to tensile failure. I think your logic is reasonable, but believe it’s always best to test the the clay and glaze combination fired to cone.

I have always been told this is a natural function of skin, predominately hands and feet and extended exposure to water. It definitely happens to me using city, well, lake, stream, and swimming pool water. The dead skin cells absorb water and expand, yet living cells beneath do not. End result - wrinkles. Today this is debated I believe (the mechanism not the wrinkles) … and there are diseases that can present other symptoms as well as similar symptoms. (See Raynaud’s disease) well water can be hard in general and often contains many more organics, not sure of any correlation there though. It is possible that city water is softer, occasionally if sourced from a river. “Chemicals” is a pretty broad description so anything is possible though, but in general well water is untreated and can contain lots more stuff than city water. For most of us I think quite common to see after prolonged exposure to water — city or well. If in doubt, probably take pictures, record what you can about time exposure, temperature, etc…. and see your doctor to be sure.

In my experience that is pretty much how they work. If you pull a lot of fresh air into your kiln you very likely will not have enough power to reach peak temperature. To me this is by design and does a decent job of capturing many fumes, but not all. Usually folks complain about the smell of wax burn off around 700 - 800 degrees. So by design they only pull a small amount of air balancing thermal load against essential exhaust. You can ramp up the exhaust a bit but the practical limit would be the air temperature entering the exhaust fan. So say 120 -130 degrees is practical at peak kiln temp using a mix of kiln air and room air. (Mostly room air) The more air you exhaust through the more power your kiln will need to reach cone.

Very cool idea, limit peak temp and get the drop and hold to heal.

Just a caution here KN95 and N95 masks will NOT protect you from asbestos fibers. Generally a respirator with an approved filter removing 99.97% of all particles 0.3 microns or larger and is well fitted to your face is required. Contaminating, your clothes, immediate and adjacent space(s) are really really important to protect yourself and others. Use appropriate caution testing first is generally the best way to know for sure.

It has a long history in the US starting in 1977 with a date of 1989 with which many consider a near prohibition for new use. In the UK, very likely sooner so I would Google for sure if you are curious of international participation. I would not assume though that the presence of a ban means it is not asbestos or asbestos containing. One thing I do know is we always presume it is and test to rule it out. The only test I am aware of that is accurate would be a bulk sample to an accredited lab where the sample is analyzed appropriately. Current (international) asbestos ban article http://ibasecretariat.org/alpha_ban_list.php

Fans and clay studios - bad mix. Two very popular ways to get this done, place the pot on an unused wheel rotating very slowly and a fan blows on the pot while it’s revolving. Old habits die hard - folks would set their ware on top of an operating kiln (usually along the edge not where it could be screeming hot). Oh, and third I have chattered things nearly right after throwing (10 min.) by drying with a heat gun while still rotating slowly on the wheel until stiff enough to chatter. Dry evenly inside and out, don’t overheat. None of these are great for the ware, but as a way to move the demonstration along ….. the bowl below was thrown, dried and chattered nearly all at once. Definitely dried out enough to demonstrate chattering.

+1 for caring! My experience - this is likely a joint failure, not necessarily glaze related. I like you, worried about the same things and once I had a similar handle crack decided to knock the handles off on a handful of my bisqued mugs and even several glazed. What I found was some handles were attached so securely that the parent material or clay would fail and the joint material remain intact on only the best made joints. From that point on - I spent quite a bit of time on making sure to compress these joints very firmly during construction to be sure the material around and the joint itself was every bit as dense as the parent clay. When I did this, the joint would be as strong as the parent clay which was the best that could be done for that joint. If I needed a stronger joint for extra rough use, then it became larger but always paying extra attention that the joint was fully compressed and attached well. A few more well compressed attachments later, knocking the handles off revealed the parent clay material would now fail before the joint actually would. From that point on I never had a failure, and often when tested by impact, the side of the mug would fail and not the joint. Good glaze helped, but glaze is too brittle to save a weaker made joint. Never had a critical joint fail after that. Typical well made and well attached joint below. This joint is fairly large but these are very custom mugs. It takes significant force but the cup will fail before this joint will. Always compress critical joints so the material is uniform strength was the lesson for me.

So it looks like you are intentionally firing short of peak cone temp, using a hold at the top to get near to the actual heat work without reaching the actual cone peak temperature and adding a drop and hold for healing?

20 minute hold usually gets you to the next cone. I am not a hold at the top fan it does nothing to tell folks how cones work. I think I would try firing with a cone pack and see where this ends up. Likely próg 02 cone 06 / 08 in about 12 hours so slow bisque designed to burnout organics. Total time and temperature are important for bisque firings. Cone 04/05 fairly popular bisque temperatures. Program 3 is close to a cone 04 fast glaze, possibly moving into cone 03 with the 20 minute hold. Program 4 appears to be cone 4 / 5 considering the hold and is also a fast glaze. Program five ends up cone 8/9, again holds usually drive the heat work to the next cone, especially a 20 minute hold. This looks like an as fast as it can go glaze schedule. While these may work for folks, they really do little to convey heat work which to me is fundamental to fluxed reactions or pottery. In my experience If you just follow the Orton chart (and instructions) and the ending speed as advertised in the chart you can hit cones pretty reliably. Once you start adding holds you need cone packs to figure out where it truly is ending up.

Just looking at this, where is the back of this kiln? Hmm think I actually see it now. I would make sure the flue passage extends to top - no leaks here. Also I think the missing member is just a tie bar to keep the sides of the kiln together and leave room for the rigid (rear) top of this kiln also missing in the picture. I think if you plan for the shrinkage (the rigid will shrink during first firing, it has LOI - they all shrink). My initial thought would be: the top, and floor extend wall to wall, the sides rest on the floor and help hold up the top. Fire to shrink everything and stuff all remaining gaps. Readjust buttons so all are as straight as practical and not overly tight, just straight. Add a tie bar and maybe make a new top out of rigid if that is missing and make sure no gaps between top and flue so the tie bar stays out of direct heat. Finally after all shrinking and stuffing, you could just lay in a second piece of rigid across the bottom, replaceable and helps with heat loss on the bottom anyway. Nice project I think definitely could perform better than new in the end!

Here are some thoughts A couple things, rigid insulation can be more conductive than loose fiber so replacing loose fiber with rigid can result in higher losses. What is the thermal conductivity of your rigid and how does that compare with loose fiber? Air gaps - huge problem, so most fiber has published shrinkage after first 24 hours - often in the range of 2-5%. Air gaps can cause crazy loses if the gaps leak enough. Those gaps look significant so unless the fiber is rigidized behind them they likely are increasing the losses through the shell. Account for the published shrinkage and layup your initial cuts with sensible overlap. Then after final shrinkage the overlapping joints can be infilled to further improve them. If they don’t overlap to form a clean joint though this is likely not possible. Compression - insulation works by trapping air. Often why loose fiber is rated as good or better per inch than rigid. Rigid however is structural so it has that advantage. It looks like the rigid is compressing the fiber though so if that is the case, this will reduce the fibers insulating value significantly. Sandwiching or compressing the fiber with the rigid will derate the fiber. I think all doable however, just need to be mindful of achieving goor air sealing and as much or greater insulating value as the kiln was designed with. So some real lookup of specifications, existing thicknesses and then adding enough thickness to meet or exceed. Finally air leakage is an energy waster, but also critical to keeping an even reduction environment. Minimizing unwanted leakage should help reduction consistency a bunch.

Common at big box stores - pretty common use in condensing furnaces and boilers. Up to 650f is what I see mostly. https://www.homedepot.com/p/RectorSeal-Hi-Temp-Red-Silicone-Caulk-57500/202809239 https://images.thdstatic.com/catalog/pdfImages/a0/a0b46b08-2550-4bd5-acd8-38b1768a8217.pdf If it’s uncured silicone you likely can remove fairly completely with most solvents, just like cleaning up after application. I assume the gasket is high temp but not quite enough to infill the gap at the kiln so it’s supplemented with silicone. “I'm wondering why most suppliers sell one for the gasket that's only rated for 400.” 600 is most definitely better than 400 but it’s at the bottom of the kiln and the pickup cup brings in outside air adjacent to this joint so this connection is not super hermetic really. What lifespan are they shooting for - who knows.

You are welcome! The hand filing was a thought to solve the overheating potential of using powered stuff

Generally rubbing alcohol or mineral spirits are adequate to clean up uncured silicone caulk. Final clean with alcohol usually removes most oil residue and also not likely to harm whatever gasket material is in use. The service temp on high temperature silicone caulk (the red stuff) is generally up to 650f. It is commonly used on gas combustion products that typically top out about 500f. Kiln shells can meet or exceed this. I would not suggest anything rated lower for this use though, most ordinary silicone is rated up to 400f

Maybe diamond file hand sharpening for doing one or two edges occasionally?

Everything is possible so to start with some observation. Your spray booth designed to code requires 100 fpm (feet per minute) face velocity. So the size of the opening of your booth will determine how many cfm you need. So CFM/ sq ft (of opening) >= 100 fpm. This will likely be 400 -600 cfm, which from the picture appears that is a dual exhaust, maybe an old above the stove type hood. If so, it likely is rated 400 cfm or so. So it seems like you can may be able to use this for a decent spray booth. Where to bring in 400 - 600 cfm of makeup air from outdoors may be a problem though. As far as a kiln vent, a typical downdraft really only discharges single digit, maybe 10 cfm. Even though they are rated much higher, all the restriction decrease their performance, and most of the air is from the kiln room and only a tiny amount from the kiln. This exhaust fan is way too large so it does not seem practical for kiln use. You might find a shared opportunity for a hood over the kiln though to remove fumes and a portion of the heat during firing. since you are connecting to an old masonry chimney, it is not designed for pressure exhaust which brings to mind a 10 -12 inch chimney liner as preferred practice. Final thing I see is a capacitor start induction motor - appears to be single speed. Being able to vary the speed of this would likely be super useful. I think it could all work, but done correctly it will definitely take decent planning to figure out the best utilization

Here is what I see Looks like multiple points of arcing and possibly some missing circuit board traces as a result of the arc.. hard to tell from the picture with certainty but if the circuit board traces are gone several components will be gone, controller highly likely needs replacement. Since these things were in a plastic box, I don’t understand what could have arced where the arrows are pointed. Loose wire floating around in the box? If true, I would examine closely before installing a new one. Nothing should touch the bottom of the circuit board. A picture of the front likely allows some component identification

@ChristopherW Ok I’ll take a shot. This was a favorite in 2018 and has been tested and used for a studio clear for several years I know of. Samples in dishwasher forever. Actually moved to new dishwasher as old one wore out. Test piece going on approx 800 wash cycles. It’s Gerstley so not so much a favorite anymore. Glazes often don’t travel well but you are welcome to it. Hope it works for you. This is one of those glazes developed taking the Katz course. The spreadsheet is his, but we have written permission by him to automate the sheet and redistribute. I think he has a new free excel sheet as well. Don’t forget use the 100% batch column.

Just an idea I would suggest following the Orton model. Heatwork prior to the last 100c / 200f is not relevant. Cones have been tested and derived for the final segment at a certain firing speed. This should be easier to code and maybe allow for offsets or a cone table that could be tweaked per application as needed. Work done prior to the fluxed reactions begin is basically reversible and not nearly as important to where the cone will melt.

Hopefully this is more helpful than mysterious. Our clays without fluxes would not melt at a reasonable kiln temperature. So proper full melting is achieved using fluxes and raising the energy of the fluxed mixture enough to get everything to melt. The melting process is not instant so it takes a combination of time and temperature to get this to happen. This predictable melting takes place in the last 200 f of the firing. Cones are made of glaze (including flux) and made to bend with the proper amount of temperature and time at their stated cone value. So a very cool way to measure this total amount of heatwork quite accurately, with one requirement. The final segment speed matches what is written on the Orton cone chart. The final segment is an educated guess as to when we have enough energy to begin these fluxed reactions. Current Orton cone charts I believe set this in the final 200 degrees of the firing, then establish based on the speed being fired what the finishing peak temperature will be. So the most important part is the final 200f and the speed you go in the final segment. 108 degrees per hour gets you the center column of the chart. Overall though, the faster you fire the more uneven a kiln can fire. Slower rates generally lead to potentially more even firings than very fast rates. For cones though and finishing, the final 200f is most important. Oh before kiln sitters and cones etc… potters learned by color of the firing. @Pres can still do this I think (appropriate IR eye protection) sadly in the old days this was a really good skill but without eye protection a likely short lived one.

Normal high temperature crimp connectors are plated but generally do not have insulation which makes them more or less high temperature. Higher quality stuff has welded seams for the crimps. You really only need to design for the area you are working in. Element leads usually use high temp wire - MG traditionally but of late we see kiln manufactures using other types of lesser rated wire but the designs have improved for cooling and use of radiation shields. I assume this is for the lid switch so matching the original wiring temperature and gauge requirement is generally fine unless it has been melting. The existing wiring is stamped with its temperature rating and gauge on the side of the wire so matching or exceeding that should be just fine. Welded barrel crimps are great but not necessary for small electrical loads IME.

Ground fault devices were created just to detect very tiny flow of current. While not exclusive most common source of leakage - damp or wet connections. In North America code generally requires them for receptacles within six feet of a source of water to minimize potential of electric shock.

Me too, rattling around on the floor, not the greatest and mounted you can use regular steel dryer duct and fittings so easy to make leak free. It certainly can go on the floor though didn’t mean to imply it had to be mounted.