Bill Kielb

Not all glazes with a decent R2O:RO are winners. A decent flux ratio indicates things could be durable, a bad flux ratio indicates likely not. I think of it as a good looking weld can be bad, but rarely is a bad looking weld good. No absolute here though. Dishwashers or Alkali testing can be very damaging to glaze surfaces. A change in visible surface gloss likely indicates significant wear. I am not sure how this translates to dishwasher cycles though. Pictures would be great, gloss meter even better and of course long term dishwasher for a perspective of actual longevity. One Thing I would try though is: you may have a glossier finish with a solid 7:1 to 8:1 Si:Al ratio. I think I would try this as well as subject some other known durable glazes to your alkali test and see how their surfaces perform. Your test is for surface erosion not necessarily for leaching. Surfaces will erode chemically and physically by stacking, cutlery, etc.

I have not had great results refiring to cone, nor do I think underglaze will act as a decent primer, but ya never know what the result will be till you try. To drastically change the look, I have fired down over an existing glaze and had reasonable success with lowfire glaze though (similar to some production wares that go to cone first to weed out potential failures in advance) so maybe an idea that is worth mentioning. Heating the ware and spraying the final glaze made even application very doable.

Interesting recipes, R2O:RO of 0.1:0.9 too far out of range for me. If you end up liking this and getting it to perform I would encourage checking the durability as well.

@s6x I think the ideas above very helpful, just need to add: Vent a kiln likely a must in your basement capable to remove the kiln off gasses and the heat produced by it. Along with that the vent will need to be able to draw in its own outdoor air for cooling. Since you have a furnace (and likely a dryer) you will need to make sure the vent can be supplied it’s own air and not pulled back through an appliance such as your furnace or dryer. when in doubt, since this is your home rated fire protection material is important. Type X 5/8” drywall has a fire rating. Drywall works as an approved rated fire barrier because the moisture bound in it is an important component of the protection. Cement board is great for its sturdy structure, but generally is not a rated fire barrier material. You are trying to protect the combustible materials of your home. So not undoable, but well thought out ventilation and protection with sensible operation to remove all excess heat throughout the firing worthwhile IMO.

It’s really important to have a connected neutral, else these kilns will not operate correctly. Maybe first confirm that you have 2 - 120v circuits line to neutral and 240v line to line. Always check you have a ground for safety while you are at it. Anything that when moved six inches no longer works likely needs a thorough inspection of all connections, contacts, etc…. Jus a reminder: Careful, use appropriate safety around energized equipment. Your diagram I believe is here https://eadn-wc04-7751283.nxedge.io/wp-content/uploads/A82WD.pdf

@SunsetBay Interesting recipe, I assume the fluxes and or feldspar have been left out. Usually 10 -15% clay is enough to keep things suspended. Up to 2% bentonite can be traditionally added to assist with the suspension when there is not enough clay to keep things suspended. These recipes seem to have more than enough clay, so why the bentonite at its typical maximum? Sometimes it’s needed, often times it’s just the result of passing a recipe onward and never removing it. Bentonite really shouldn’t add to the fired result. So, you may be able to reduce or eliminate it eventually and you have so much EPK that calcining a portion of it could improve its ease of application and reduce its tendency to crawl. Looks like 10 - 15% of the EPK could easily be calcined and tested to see if this behaves more to your liking.

I think if you post the recipe there will be folks here advocating calcining high shrinkage components if present, rather than adjusting the viscosity. You will definitely get ideas. Maybe repost as how to fix a glaze that crawls?

Crawling is usually a function of the fired surface tension (how well a glaze can heal) so most influenced by application: thickness, cracks while drying ….. and less influenced by firing schedule. Some glazes tend to crawl while others heal really well. I would look at application as the likely culprit.

It seems to have three phase specifications: 3 phase 220v expect 2.2kw. And so on. Although I think I am looking at a contactor though, not necessarily the kiln rating. Understanding how this is currently wired, it’s actual measured operating amperage would be helpful along with the measured resistance of the elements and how they are connected to get to the actual wattage being supplied. From there We have typical watts per interior area conditions that would give an idea of capability. Maybe easiest: If you can measure the actual amperage we can just figure the wattage.

If your glazes like it, 6-6 1/2 hour firings are fine and not overly fast. If your results tend to be better with longer firings, then by all means easy to slow down. If you make very heavy sculpture etc…. Then slowing down may be a concern. My normal wares can go very fast with good results. Effective bisque firing is dependent on time, so some clays perform better with a long schedule to burn out all the organics. Easy to slow down though, just extend your switching times.

The basic problem, the amount of energy you are putting into the kiln is not sufficient to offset the energy leaving through the kiln shell and that required to heat the wares to temperature all at a reasonable speed. The shell looks decent, no holes, missing insulation So, was the kiln designed or is rated to fire to your desired cone? Are all the elements working? Are they within 10% of the original resistance? Is it operating on the design voltage …. Maybe start with the what it’s designed for part, does the kiln equipment tag state top temperature? Usually a cone 6 kiln needs to be rated more (cone 10 preferred) to be able to repeatedly hit cone six as it wears. If maximum temperature is cone six, then after a few firings and regular element wear it will not. So good to find out the rating first which often is on the equipment tag. Next, if rated appropriately can you measure the element resistance and compare to new. If the elements have worn by 10% typically they will need to be replaced to make it to the intended design temperature in a reasonable amount of time. Generally elements wear together so all are replaced when found worn.

It may work out for you, but for many home studio artists my observation - most not measuring viscosity, with only a reasonable amount measuring specific gravity of glazes for repeatability. When younger and spray painting custom finishes Zahn cups / Ford cups (in North America) were convenient, economical and repeatable enough. Hopefully you can find a niche use in pottery. Very cool project.

I think Neil said it. For the controller I would add that it will take a bit more electrical wherewithal than just the previously contemplated switch change. Some things to think of: using an old controller for both kilns also appears your kiln likely becomes single zone and provisions to move the thermo couple from kiln to kiln becomes necessary. Converting the Euclid to 240 v is pretty straight forward, new elements, adjust the transformer primary jumpers to run on 240 v rather than 208v and you are pretty much good to go and fully functional with a high fire kiln and it’s controller. The Duncan is marked as cone 8 and already a sitter kiln. For simplicity and two working kilns I would be inclined to just change the elements in the Euclids and go the switch route for the Duncan as a mostly bisque kiln.

Not sure this helps but …. Sounds like your friend errantly bisque fired to cone 4 instead of cone 04 ( we have all done it) cone 04 = 1063 f (sintered and absorbent) cone 4 = 1162 f ( starting to melt - explains why things stuck together elsewhere) lowfire cone 06 - 04 often used to bisque low, mid and highfire clays leaving the body sintered open and ready for decorating, but a bit sturdier than greenware.

What comes to mind is as a general rule 0.15 boron ought to get you a cone 6 melt regardless of source. And maybe search Glazy.org defining the characteristics and color you desire. (Example below)

Technically not hard really. 19 amp kiln, minimum = 19 amps x 1.25 = 23.75 amps minimum breaker size. ….. and ….. 19 amps X 1.50 = 28.5 amps Maximum breaker. So a 25 amp breaker fits in the range best. 30 amps is a bit over. You can simply swap your 30 with a 25 and be compliant. So under NEC: for a continuous load not less than 125% nor over 150% Kilns are considered continuous loads. Normal breaker sizing for non continuous load is: not to exceed 80% of the breaker rating, really just the reciprocal of 125% anyway. So non continuous allowable load on a 20 amp breaker =0.80 x 20 = 16 amps your instincts pretty decent really, I assume you did not think good to run a 20 amp breaker maxed out.

Good Find! Yes that Truely calcs to just under 19 amps. Unfortunately a 30 amp breaker is a bit above 150%. Interesting old unbalanced design.

@Ksmith Not sure where these come from - closest I got was an 1814 hp. With the elements below and at todays 240v system voltage this pushed your breaker requirements to: (minimum) prox 25 amps x 1.25 = > 31 amps and maximum 25 X 1.5 = <= 40 amps. So for below, 35 amp breaker and wiring minimum. Just suggesting, after you get your new elements, double check the required breaker and wire gauge by verifying the total actual resistance and solve for the current from above. Your requirements ought to be: equal to or greater than 125% of the load but less than or equal to 150% If you consult an electrician this needs to be sized as a continuous load.

My thought is .2 for the power cord is too high or a meter measurement issue. Usually elements are worn and won’t make cone in a reasonable timeframe if they increase by 10% cold. So the symptoms and measurements say new elements. To know the “hot” resistance you need to accurately measure the voltage and current and do the math. BTW - North America nominal voltage these days is 120/240, 220 is virtually non existent. Just curious if you warmed them up and made sure they are all glowing first.

Just asking, are these finished with a swirl in the bottom as appears in the second picture. It’s really hard to see these cracks, maybe you could post some additional pics as examples here.

Not saying this is her method but I think I would just texture the clay and paint the designs with underglaze. Clear glaze over the top might even get me some minor movement especially if sequenced to encourage.

For me,I go with mg @ 450c but shop the web. Usually 20-30ft of #12is a lot of replacement though. I just shop the wire suppliers for best price. $28.00 handles a lot of repairs for me.

Complicated question actually. Optimal operation is often considered 40c - 50c (105f x 122f). (For reference - 120f hot water is considered reasonably safe but feels VERY hot to the touch) most circuits are designed around the lowest rated connection in the circuit. Starting with 60c and has grown to 75c and 90c over time as materials improve. 150c rated wire nuts are often categorized as plenum rated. Ceramic wire nuts generally have higher operating temperature ratings. So exceed or meet 60c would likely be a material minimum requirement. Best answer I can give, run everything as cool as practical. As things heat, resistance generally goes up which means a local voltage drop which means some watts locally which means more heat locally …… Proper sizing and proper cooling are the best ways to minimize this. Wires rated higher in temperature will last longer, which is why MG would be better than lesser rated insulation. Passive cooling is dependable so that updraft thing is very useful dependable and free of operating cost but very dependent on ambient temperatures. Kilns are weird animals, the element connections approach 2000f so better convective cooling helps the longevity of this connection and can enable lesser rated wires to operate satisfactorily. Element end connections can often be preserved longer with a bigger heat sink type splice just because of the additional cooling area and of course any improvement in convection helps lower the average temperature of this splice. Old designs 60c, UL now I believe requires 75c for lugs / breakers. So all components can be designed to meet or exceed the lowest design temp in the circuit ….. which is often the lugs and breakers in the US. A nice brief explanation of NEC temperature https://iaeimagazine.org/2009/september2009/where-a-successful-installation-begins-and-ends-understanding-nec-rules-about-wire-temperature-ratings-terminations/ A bit lengthy but the point is, lowest practical temp is generally best for longevity

Separate box great idea!. Cooling from bottom to top still applies. Just a note, if installing wires through holes use appropriate bushing or electrical connector. Never wires through a hole in the steel. Chase nipples are cheap and an electricians safe way of routing machine wiring safely through an opening.

Yes that U shaped piece divides the space it does not need to be heavy, just reflective. Making it heavier will not add to its effectiveness as a reflector. Making sure ventilation air can travel freely from bottom to top will though.