Bill Kielb

How do you know it slightly underfired? It’s a manual kiln so 2 hours on low, 2 hours on medium, then high till end of firing and see if this gets you in the 5-8 hour range.

All very available HVAC ductwork parts, available stuff - For that fan You should be able to use a 12” flanged take off, 12” hard pipe duct and or 12” flex duct to isolate vibration or as needed. Steel duct attachment would be 3 screws for round rigid, worm drive clamp is easy and goof proof for the flex. Seal all seams with metalic duct tape UL181- P for rigid or UL181-FX for flex connections. Duct sealant (brush applied) is more permanent than tape but taking it apart for maintenance a bit of a pain. Advise adding a decent backdraft damper and well thought out discharge louver. Cheapest flanged take off I could spot below: The take off from the original OP appears to be a bit adapted for use (might be the photo), connection shown below, typical.

Just so you know a little of the where and why of all the caution here, electricians seem to have difficulty sizing breakers and wiring for kilns. The general rule for kilns (known as a continuous resistive load) is simple in that not less than 125% of the rated load, nor more than 150%. Your kiln is 48 amps so a 60 amp breaker and wiring is recommended by the manufacture and fits this rule. For everyday stuff, Electricians are usually taught never to load a breaker more than 80%. Brand new from the store, they are rated at 80% of their load. In your case a 50 amp breaker typically would only be used for a 40 amp load following this rule……... So that ……. somehow a 50 amp breaker was used coupled with the initial 120v hookup of a 2 pole breaker raises flags as to how it was all done.

Dick has a great point remember no skimping! As long as we are covering the electrical bases, the ground wire is considered an equipment ground. It is sized based on the maximum load on the circuit - 60 amp breaker- and should be sized a minimum gauge by checking in table 250.122 (NEC). Your electrician should know this and verify, but a 60amp Equipment ground needs to be #10 or larger copper wire by memory but don’t trust my memory - double check. No skimping here either. Come to think of it ALL the wire needs to be copper, JIC he is using or planning on something else.

14-50 R is still a 4 wire device rated at 50 amps. Just checking you are squared away seems your electrician is not familiar with a 3 wire 240v circuit. You should have: A 2pole 60 amp breaker, #6 wire and three wires are run, 2 hot wires (L1&L2) and a ground wire (No neutral for this type of circuit). Must have a ground though to protect you. No skimping, these are the manufactures requirements.

It would be interesting to see just how many departed significantly. Lots of old glaze recipes fall into a reasonable range around 0.3:0.7. I would love to see real comparison data on this, anecdotal often has the potential for perception bias.

Maybe food for thought - since it’s really hard to maintain temperature and lower the gas as well as shuffle your dampers to maintain reduction this might be a very small / slight drop and hold actually. Especially if you are not significantly dropping the next cone. Maybe an idea to explore - drop and hold pretty popular to heal some pinholes. Might lead to establishing an easier end of firing sequence.

I would definitely agree - it should not be viewed as a rule for sure. Even Katz believes working within a range is practical. Definitely more research, but something to help design within and when significantly outside a reasonable range that knowledge would hopefully cause folks to investigate. For folks that are science oriented, proving something true is usually impossible just because all conditions never can be accounted for. From a design standpoint I find it as helpful or a bit more than relative references we see in glazes such as High, as in high alkaline - how much is high, who knows? Same with high calcium matte or high alumina matte. They are all somewhat helpful references though as folks sought to characterize for the benefit of others so totally dismissing those efforts probably not productive or fair. So more successful testing under as many conditions as practical likely would increase confidence for sure, dismissing the results entirely, without reasonable contrary testing probably not the best path either.

Just a thought- You may want to set you SG first for what works best with the particular glaze ( Not necessarily a predetermined number) from there you may be able to adjust viscosity as needed to improve performance.

I am not a hold person as to me it simply adds heatwork. In a practical sense there are folks who fire one cone lower but add a hold to get to the next cone heatwork without the peak temperature. In that case firing to cone five with a fifteen to twenty minute hold often gets one to cone six. (Usually verified with cones) Why do that? Some glazes do not like higher peak temperatures. Some underglazes change color significantly with peak temperature. It is a pretty functional way to fire a cone to two cones max higher without hitting the actual peak temperature. Firing higher or for longer has never healed pinholes for me, often made them worse. Drop some temperature and hold however has helped on s some of my pinhole situations. whatever works for you and your desired glaze results is likely the best answer. Whatever is done, I strongly suggest always nice to have cones in place so you genuinely know how much heatwork was done. As to suggested time, 15-20 minutes generally gets you to the next cone.

Not to worry, folks have made glazes forever and experimented looking for predictable ways to characterize what happens. They publish their findings or research and you get to decide if it is useful to you. Commercial glazes have the issue of - what is in them and how does one correct a defect such as crazing. The good part is commercial glazes don’t use lead anymore (for the most part), vanadium pentoxide etc… generally because someone found out it was a bad thing. If you mix your own then you know what is in it and can reasonably test for durability, fit, etc…. to your satisfaction, before selling it or giving it as a present for human consumption. I think it does help to inform but definitely not for everyone.

Sorry the reason I mentioned the firing to cone 6 making a cone 04 glaze less durable because it was a good example that durability and boron were not tested or at least meaningfully tested and meaningfully quantified. I also mentioned it because many 04 glazes will fire just fine to cone 6 - Stroke and coat and look alike glazes seem to fall in this category. The only point was, while excess boron is certainly a thing, we generally should not conclude the current research predicts durability, hence the example that using it to predict an 04 glaze durability fired higher seems to be at odds using it to strictly predict durability. I do not think that was the focus of the 2012 research. Instead we were given a reasonable amount of research that indicated flux ratio’s outside a reasonable range could indicate a lack of durability. Why design your glazes there? Maybe test durability of those glazes approaching less reasonable ratios with a heightened awareness of the potential to be less durable. The gloss test is a doable one and relatively repeatable (if you have a decent gloss meter and maintain uniform measurement protocols) but it is dimensionless really so as a practical indicator and even trend indicator, likely fine. It is dimensionless so maybe no direct predictable correlation to longevity of service. I think the flux ratio research has shown merit and potential to be reasonably useful as qualified above but Boron and durability has not necessarily been tested and quantified. So I believe appropriate to say, why waste the material it’s not necessary to use that much. I do not believe what was written in 2012 was intended as a durability study on Boron in glazes……… just an indication of where did they appear best to melt.

Fire in the kiln? Could be a bit of smoke.

Gas fired appliances need ventilation, the simplest form would be a properly sized natural draft hood. Natural draft hoods are one of the simplest designs because they are simply a hood above the appliance with some space available for dilution air (room air) to also rise up the flue pipe. This open space on older natural draft appliances (boilers, water heaters …) was often called the draft diverter. Quite often before the flue could warm sufficiently this space would allow the cold downward draft to be diverted so as not to blow the pilot out in the off cycle. What COULD it be? Common would be a properly designed flue for the kiln not allowing the cold backdraft at startup. You mentioned HVAC issues, well gas appliances need their own source or combustion air as well sized for the appliance and positionally sized in one of several very specific ways to combat stack effect, dilution air requirements etc… Further: exhaust HVAC appliances need makeup air. Proper design and accounting is important so as not to defeat any natural draft appliances. Does the studio have a paint spray booth or other exhaust appliance affecting this? What could this be? It’s simple stuff but takes real design experience and the potential to be a real health safety issue with carbon monoxide or just a nuisance issue like pilots blown out exists. My experience often these are designed by folks not skilled enough to do so or a failure to follow the manufactures design requirements. Hidden issues like other exhaust appliances with makeup air issues are common as well. If folks are silent or secretive about it, maybe they are not skilled enough to understand all the potential design issues. It’s fairly straightforward but truly requires combustion air zone training in addition to flue design skills. I can’t tell you how many times I have seen direct vents installed for natural draft. My best thought here is find an HVAC contractor with these skills and the ability to understand and follow code requirements. The solution is generally easy, just not necessarily intuitive and unfortunately found more in older techs than younger as these appliances disappear from use in favor of sealed combustion higher efficiency stuff. zI could be several things unfortunately, I included a simplified drawing of some of the interactions of these required airflows you may find of interest in this thread https://community.ceramicartsdaily.org/topic/39240-skutt-envirovent-still-allows-fumes/?do=findComment&comment=251190

I would test, should be fine with the silica but I think I would default to alumina for more worry free separation. Watch everyone else’s wares though, easy to get this on other folks finished work. Folks often add Alumina to their wax for more control of the application however burning out large quantities of wax requires big ventilation so the alumina wax is a nice solution for keeping lids from sticking but probably not so much for separating sheets

Not arguing actually Whether in his class or reading that paper 14 of the 16 pages were devoted to flux ratio. I just don’t think his primary focus was testing durability and boron levels. The one graph we have in the paper shows reasonable minimal gloss degradation from about 0.15 to 0.2@ cone 6. The low point at 0.15 out to let’s say 0.2 With confidence. His demonstration that durability and temperature independence of flux ratios however was a notable central finding which likely gives greater confidence flux ratios can be a leading indicator of durability. Can there be excess boron - certainly, yes. If I take the original recipe at 0.63 boron and simply apply Katz’ boron melt chart and fire to cone 04 it becomes durable? This research to me was not to establish that. It might just be my reading of 14 of the 16 pages though.

I would agree, the more the merrier. Gloss meter readings were an interesting indicator and something easy to replicate. Not really indexed to a quantifiable amount of degradation though. Still it likely is indicative. Stull correlated silica and alumina to a fixed flux ratio, but yes in clay there are an infinite number of fired combinations to which research could be applied.

Yes, he found an ideal boron level at cone 6 but really read through the beginning part of your citation, first several pages all refer to flux ratio, graphs are about flux ratio and his examples provided within the course are about flux ratio . If you took the course and have the notes lookup a glaze he termed Gel-o where he said “ At this point, I don’t see a reason to take functional glazes past 0.35 R2O : O.65 RO”. I feel If you are dismissing the flux ratio as being a significant primary part.of that research you are missing a significant important point. The boron research was centered on how much to melt at what cone. He concludes with a broader range for cone six, but again the ideal flux ratio is first and foremost.

The Laguna info on that glaze says it is a cone 5 matte recipe, also available in a gloss version.

Katz’ research with boron was about melting point. His research about durability was: is there a reasonable flux ratio and being outside this ratio ….. likely non durable. Boron glass / glazes can be very robust and properly formulated low fire cone 04 glazes have tested very durable. The published chart was for melting point and not necessarily durability. Article here: https://ceramicartsnetwork.org/docs/default-source/uploadedfiles/wp-content/uploads/2008/10/tf-boroninglazes-0912.pdf The first part of the presentation cited is about flux ratio and implied durability. “The graph on this page shows the amount of boron required at any temperature. The purple-blue areas are underfired, while the red/ orange areas are very glossy. The vertical axis is temperature in celsius and the horizontal axis is UMF boron additions to a standard glaze. By finding the desired temperature and determining the position on the oblique line, you can figure out the corresponding required UMF boron level at that temperature. This chart applies from cone 06 to cone 10. As a general rule, we define the required amount of boron as an additional 0.1 mole (via UMF) of boron for every 50°C below cone 10 (1305°C). Boron is an exceptionally good material for adding to glazes as it makes glasses at lower temperatures that are just as strong and resistant to wear and chemical leaching as the best cone 10 glazes.”

Can they have an unglazed bottom or foot ring to allow for display? If not, how about casting a sacrificial ring or tab (maybe 3/16” diameter eyelet) into the bottom, suspend while firing, grind off after finished and finish the remaining dot with paint, or a bigger dot and insert logo? Just thinking …….

I think that might make sense. I think I was assuming the relay was not making any activation noise or a click could not be heard. If the solid state relay is not functioning then your elements would not heat up even with the relay functioning. Hopefully they can recalibrate your controller and update any software patches as well. Sounds like you will finally have this solved.

Since this all started with the Tap screen recalibration, it seems likely that it is the issues solve first. The tap executes a calibration routine after holding your finger in one place for 15 seconds I believe. Software updates may effect this as well so probably good to be in a position to get this connected to the net if not already connected. Not being able to start this kiln by controller is definitely an issue before checking other parts.

Good practice. Worn connections usually will reduce power in the kiln and not necessarily make your breaker trip. Definitely fix the connections though - see this fairly often as well. Pictures of main power to kiln and a decent repair below just as an fyi.

Yes, can you manually operate it with your finger. Push the plunger down until you hear a click. If you hear a distinct click then hold this down and see if your inside relay will fire with this held down. If that all works you need to physically see what needs to be done for the lid to engage this switch when the lid is closed so that the switch is depressed enough so that same click is heard. This is a roller safety switch which I believe Is non adjustable so whatever depresses this is often the adjustable portion. If this all works then great, to troubleshoot further is not hard but will take a bit more writing space. BTW can you confirm the 3 amp glass fuse is fine? Very fine wire so you likely need a meter to check it has continuity. If you have power to your controller some way, then that fuse is fine.