Bill Kielb

Hmm, I don’t not know if I fully understand. Underglazes are not glaze and often consist primarily of clay and stain. Many do not really melt so unglazed they are very matte but more sintered than melted hence durability or longevity would be difficult to guarantee. For a gloss finish it’s common to apply clear gloss glaze over the underglaze. For matte appearance with reasonable durability it’s also common to use matte clear glaze over the top of the underglaze. Any clear matte will cloud to some extent because of the diffraction of light. Thin application definitely better than thick as far as glaze clarity. As far as a glaze that works for you and your clay and the desired finish you will likely need to test. If you look on Glazy.org Marcia’s matte https://glazy.org/recipes/19734. Was created to be very dry ( but easily adjustable) and melt over fairly heavy underglazes. It has great reviews, but it may not work for your clay, desired aesthetic, etc…. Sadly clear glazes often tend to take testing to meet an artists needs. There are many matte glaze recipes though - which one works for you will require testing.

I like all the ideas. For anything a bit uncertain I favor a rough opening done in pipe so it can be pulled later but the number 6 takes care of that. I would suggest terminate in a 4X4 box for working room for now. Cover plate typical below. (Duplex drywall ring typical) a single gang box would be tough to work in when you install the receptacle.

One idea that comes to mind using underglaze, you can free form your initial design on greenware and bisque fire. The piece will contract a bit and your strokes will become more dense on their own. From there it is often enough, but if not then adding a second coat to cover often gets folks there. Stay between the lines to keep the original form true or judiciously accent and over paint the design to preserve brush strokes and depth. The second coat is a precision thing I know and not for everyone. The point though, when applied to greenware, just bisque firing it may get you the density you desire ……. or at least close, or maybe something to experiment with. I think the pot in the picture could be recreated on greenware and likely not need touch up and a second bisque.

Just a few things to suggest to start with. I would suggest laying out as best you can where the kiln will go. There likely is only one logical best place that you will place it. If you can do that, then roughing a circuit in for a future kiln and ensuring it Is 3/4” pipe (raceway) rough opening will allow you to pull the appropriate size wires when you get most any kiln. Now, where the kiln will go - probably adjacent to an outside wall, most likely in a corner so there is decent access to ventilation outdoors. You should not combine systems, this one is for the kiln. You should decide if you intend to remove the excess heat as well as all the fumes or a portion of the fumes as in counterflow systems you will likely need electric at or near the kiln for the ventilation accessories you have chosen as well. So maybe another rough electric opening in pipe to be pulled at a later date. Maybe another 3/4” rough opening so if you decide on full ventilation just about any wire size ought to fit. depending on your ventilation choice above you will likely need to plan on makeup air from outdoors as well. So just some things to start to think of

Yes of course simplicity is best. But I would suggest you re-read my original response directly addressing his post. Elaboration came as further requests were made. My first answer was intended to be reasonably brief but also a reasonable explanation to his question: “Is it correct to say that if a glaze/clay combination does not craze at cone 5, then it should not craze at a higher cone firing?” And his direct follow of working at cone 6. With due respect as well, I certainly apologize if I fell short of that goal in your view. Unfortunately my original answer was to the best of my ability an honest attempt to achieve that.

I really do not - just responding originally to the OP and your specific question. I have fired a bit and never did I notice firing higher cures crazing. That’s just an observation though. The reason I believe what I believe is outlined above but it’s just an opinion with a basis. Start a new thread, maybe you have something and firing higher is another tool to help with crazing.

Crazing to me is a result of the differences in the rate of growth or shrinkage. Once fired clay and glaze are the same size, so the clay has shrunk to what it will be and the rate of future expansion and contraction will be affected by its composition and its physical (and thermal) properties such as density etc…. Firing the body to its rated cone will provide the best chance of a fully melted body with repeatable characteristics. So the COE will likely be different for a cone 6 body fired to cone 4 or even cone 5. Our glaze on the other hand if able, may tolerate the difference in speed of expansion / contraction and not fail or craze as if pulled apart. As a glaze is fired higher will its COE change? Very likely yes. Will its physical characteristics change? Very likely yes. Glazes more resistant to wear as in surface hardness may fail more so in impact. I think the difference here for me, none of this is about the starting size and all about rates and whether the glaze can keep the clay body in a slight bit of compression without the glaze failing. So firing both to their rated cone likely gives the best repeatable representation of the match for both. Firing lower and assuming the next cone higher will improve the COE match between the clay and glaze is likely not really reliable in my view. So in the end, fire to rated cone, firing to lower cones is very likely not a good indicator for how these materials react when fired to rated cone.

I have not torn one apart but I would check the belt tension for sure and zero the pedal. The traction drive appears to be a part of the motor, so you might find complete rebuilt assembly. Here is the best in depth maintenance manual I stumbled across. https://cdn.shopify.com/s/files/1/0010/1931/4239/files/rk10-troubleshooting.pdf?14401615399485494650

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?