Dick White

Ask your building supervisor, and particularly, the electrician to get out their code book and look first in Article 100 (Definitions) where continuous duty is defined as 3 hours or more at full load (i.e., your kiln on high as it finishes the firing), and then at Article 210.19 (A)(1)(a) (Branch Circuits) which specifies that branch circuits supplying a continuous load must have an ampacity of 125% of the continuous load. You may not be considered qualified to argue with the electrician, but the electrician must follow the code. Good luck with it.

As Neil notes, 15 hours is an average time for a 1227 in good condition. We have 2 of them dedicated to glaze firing at the community studio I manage, and the timing generally is around 13-14 hours when the elements are new. As the number of firings progresses, the times stretch out to 18-20 hours, which sometimes exceeds the time available on the dial. That is the clear indication I need to requisition funds from park HQ for new elements. So, in this test firing of your kiln, be prepared for it to take more or less time than expected based on potentially unknown condition of the elements.

Are you wedging/kneading the clay when you take it out of the bag to roll the slabs? Clay fresh out of bag will have invisible tension rings in it from the auger of the pugmill. If you slice off a piece and immediately roll it into a slab, those tension rings will still be in that slab and cause cracks as it dries. Wedging/kneading is important for both wheel thrown and handbuilt work.

Jumping back in on this latest wrinkle in the question... As dh notes above, the technically proper representation is 1.46, as the technical definition of S.G. is the ratio of the weight of the slurry to the weight of an equal volume of plain water. 100ml of water weighs 100g and (in this example) 100ml of glaze weighs 146g. So, 146÷100 = 1.46. If you are using a 100ml syringe to weigh your glaze on a digital scale, the number on the screen is the S.G. after mentally shifting the decimal 2 places to the left. I would guess that some might just say ".46" because the 1 is implicit for glaze slurries that are heavier than water, or maybe call it 146 because the location of the decimal isn't that important. But moving on to the 2-digit number "46", you may find yourself in deep doodoo. In the mid 1760s, a French pharmacist named Antoine Baume "invented" a hydrometer scale for measuring the density of his liquid potions. That scale was based on the density of salt water, and is generally expressed as "degrees Baume". By whatever coincidence, 45 degrees Baume is 1.45 specific gravity. However, the rate at which the Baume scale increases or decreases is different than the rate at which technically proper S.G. changes. Consequently, terra sigillata at 1.20 specific gravity is about 24 degrees Baume, and casting slip at 1.80 specific gravity is about 64 degrees Baume. If you are using a commercial hydrometer, it may or may not have both scales marked in it. I have several hydrometers that I never use (because 1. they are notoriously inaccurate for mid-fire glazes, and 2. the 100ml syringe is so much easier) that has both scales marked on the insert. But one of the large community studios that I teach at has 2 hydrometers sold by Laguna Clay that are scaled in degrees Baume only. The glaze recipe book there specifies a 2-digit number as the target "specific gravity" for each glaze. As long as nobody enlightens them about the technical truth behind that number AND they continue to use the same hydrometers to measure their glazes, they will be okay. But heaven help anybody who takes that recipe and supposed specific gravity somewhere else.

The specific gravity is a measure of the ratio (by weight) of the glaze materials to the water in the slurry. When applying glaze to bisque, the water is immediately absorbed into the porous ceramic while the solid particles of the materials are trapped on the surface because they don't fit through the pores. If there is too much water in the slurry (the specific gravity is too low), the bisque will become saturated before enough glaze materials have been deposited on the surface. If there is not enough water in the slurry (the specific gravity is too high), the glaze materials will overload the surface of the pot before much water has been absorbed by the bisque. Both conditions will adversely affect the outcome during the firing. Once the specific gravity has been adjusted to the proper ratio for that glaze and that particular method of application, the viscosity of the slurry can be adjusted with a flocculant or deflocculant to achieve the desired creaminess, thickness, runniness, or whatever you want to call that aspect.

The obvious main difference is melting temperature. Do you know what temperature your enamels are melting? I don't know of any enamel recipe books, but with the slight amount of enameling I did with my Mother years ago, the enamel powders were previously melted glass ground to a fine powder. I doubt that conventional glaze raw materials would work at the low temperature; the various materials melt at different temperatures and so you have to take them to a fairly high temperature for them to melt together into the vitreous glass. Whether you could fake it with ordinary Mason stains, dunno but might be worth a try since you already have the equipment for enamel work.

Elements produce heat as a function of their electrical resistance at a particular voltage. Their construction is a function of the length and diameter of each coil and how they are interconnected (in series or in parallel). A replacement set can be constructed only when all these factors are known. You might seek the recommendation from your local pottery supplier for someone or local company that specializes in the construction of kiln elements. I only know of sources here in the colonies, I don't know of anything on your side of the pond. The rating plate as in your picture only assists the electrician in knowing what sort of wiring and receptacle to install for powering the kiln. Perhaps one of the group members from the UK can give a better suggestion.

Conventional wisdom points to elements being worn or broken. To test if an element is broken, slip small scraps of paper behind/under each element and turn the kiln on for about 5 minutes. If an element is heating, that scrap of paper will be scorched. If an element is broken or not heating for some other reason (such as the relay is failed in the off position), that scrap of paper will not be burned. Some kilns can manage to get to 1000℃ with one element out, but can't go further on partial power. If all elements are heating, then the probable cause is the elements are too worn to produce enough heat to reach the higher temperatures in the firing. Replacing worn element coils is done from inside the kiln, so don't worry about the welded case. You will have to remove the controller box to expose the electrical connections of the elements.

With all due respect to Occam shaving with his razor, aren't we complicating things here? Move the picture to your desktop or wherever you keep pictures. Right click on the picture, and one of the options in the top group is "Edit with Paint 3D." Click on that and the picture will open right into Paint 3D. I'm not going to engage a debate whether the new Paint 3D is better or worse than the old Paint (or that both are abominations), but it is Win10's default built-in raster image editing program. Once in Paint 3D, the crop tool is right there above the image. Click on the crop tool and the image will be surrounded by a white line with little white circles in the corners and midpoints. Push any of them in with the mouse to change how the white lines enclose the part of the picture you want to keep. Click Done when you like it. Then click on in the Canvas item in the tool bar across the top. This will surround the image with square white dots instead of the round ones in crop mode. With your mouse, drag any of the corner spots inward and the image will shrink. (Don't use the spots in the middle of a side - they will squish and distort the image. We just want to smallify it.) When done with this step, go to File and Save As to a new filename. This preserves the original in its full bigified glory. Find the new picture (yeah, Winblows will always put it somewhere you can't easily find it), hover your mouse over it and the preview box will show the file size. It needs to be less than 1 MB to be uploaded here. If the new picture isn't small enough yet, rinse and repeat with the canvas resize feature.

Did you mix it while you were adding the dry plaster to the water, or did you pour the water over the dry plaster and mix from there? The proper technique is to have the measured amount of water in a large mixing container and gently sift the premeasured amount of dry plaster onto the top of the water and let it sink. By the end of the premeasured dry plaster, it will likely be sitting in an underwater "mountain" that nearly reaches the surface of the water. Let it sit there to slake for a few short minutes, and then mix it. It will be creamy, and then you can pour your mold. If you mix it too soon or too much, it will curdle and begin to set instantly. Another possible fault is mixing in a container previously used to mix plaster but was not completely and thoroughly cleaned. The previously set plaster remains will instantly set off the chemical reaction of setting in the new plaster. For this reason, I tend to mix the plaster in a bucket into which I have inserted a plastic trash bag. It will be a bit trickier to pour the plaster out, but then I can just throw away the bag.

Something that I think gets lost when a non-science person looks at these downdraft kiln vents is that the how venting occurs. The fan does not directly suck fumes out of the kiln. Rather, the fan at the other end of the vent pipe is pulling a significant air flow through the collection box which causes a slight suction through the small holes in the bottom of the kiln via the venturi effect. If the intake holes in the collection box are blocked, there is no flow through the pipe to the fan and the fan just spins in static air. With static air in the vent pipe and collection box, there is no venturi suction down through the holes in the kiln floor. One difference between the Skutt and L&L versions is the Skutt collection box has an intake hole that was designed for a reasonably appropriate airflow through the box, but is otherwise not adjustable. The L&L collection box has an adjustable shutter that you can tweak the amount of air flow through the box to get just the right amount of suction through the holes in the kiln floor as determined with the match flame test. Note that the system only works if the piping from the collection box to the fan is in good airtight condition. If there are unsealed joints or corroded holes in the pipe, the fan will pull air through those closer holes before pulling air through the collection box at the other end, reducing the venturi through the holes in the kiln floor. Gaps around the lid and between sections do not change the venturi through the holes in the kiln floor. Those gaps simply provide the make-up air going into the kiln as fumes are gently sucked out the bottom. There are enough such gaps spread throughout the kiln body that watching for changes in smoke intake at a peep isn't meaningful.

The wiring diagram is here: https://paragonweb.com/wp-content/uploads/A66WD.pdf The diagram clearly indicates a 4-wire power cord/plug with neutral and ground (and a few wire nuts are also specified). The last picture in the series just above, showing the open (and broken) 10-30 plug, I see the green ground wire in the power cable has been snipped off, which makes the whole thing unsafe with no ground.

These old Paragon kilns are wired differently than most kilns these days. They are 120/240V, meaning some of the time the switches cause the elements to run on 120V and other times the elements use 240V. Consequently, the 4-wire plug and receptacle with a neutral is essential. The kiln will not operate properly on a conventional 3-wire 240V circuit. As Marko notes, a 30 amp circuit is minimum, but 40 amps is maximum. The outlet on the top of the control box is actually 120/240V, and was intended to power an extension ring if desired. Otherwise, it's not good for much else. As for digital controllers, the external wall-mount Skutt KM-1 is not suitable for this kiln. It will only work with a straight 240V 3-wire cord with no neutral. As noted, this kiln requires a neutral. The Orton AF4000 wall-mount controller can be special ordered with the 120/240V circuitry. If you are adventuresome and facile with electrical wiring, you could replace the kiln sitter mechanism with an Olympic ElectroSitter.

Fine with me too. It's an interesting additional level of glaze chem. Thanks Bob for originating it.

Just a sorta-humorous note along these lines... We had been talking about this, and though the college studio where I am a studio monkey was closed because of the pandemic, I suggested to the professor that she should order some to get us through the however long the shortage might be. We reopened yesterday for modified in-person studio work, and there on a cart were 4 bags of it, enough to last us the rest of millenium.

Gare Kilns were taken over by Evenheat. User manuals for the old Gare kilns aren't among those published on the Evenheat website, but if you call them, they are helpful and can get the old manuals out of their archives for you. As for the capabilities of the kiln, some of that should be listed on the electrical rating plate that is attached to the side of the kiln or the control case. If you post a picture of that, we can see what it looks like. dw

Having dabbled in crystalline glazes more than a few times, my understanding of the process is there is way way way too much zinc (25%+/-) in the recipe for a "normal" glaze, but it is all incorporated into the melt at peak temperature in what might be similar to a supersaturated solution. There is very little calcium or alumina so that the molten glaze is nice and loose (runs like the dickens) for the crystals to grow without any impediments. While the silica molar level is low in absolute terms, with almost no alumina, the Si:Al ratio is over the moon. As it slowly cools, the zinc molecules precipitate out and readily find the excess silica molecules to form and grow the big zinc orthosilicate crystals during the multi-hour hold at temperature. I will try to put in a picture from EU-Cal of one of my recipes. The excess silica is 7.55 and excess zinc is 3.44. That stuff has to go somewhere, so it forms crystals. The crystals also absorb colorants that are in the recipe, but in a standard order of electron valence, leaving some of them in the background. I have not tried a reduction firing, but those crystalliers who have report it's a hot mess if reduced on the way up, but if there are reduceable colorants in play, they will do all sorts of pretty things on the way down after the crystals have formed. (@BobMagnusonAwesome tool, btw. I will be sending you a request message later.) EuCal_ver1_9dw.pdf

Well, actually, there is a problem that is specific to the Shimpo Whisper, Giffin has acknowledged it and is trying to develop a solution. I don't know the progress on that. The physics principle involved is that when you accelerate the wheelhead, the differential momentum of the accelerating wheelhead (which the lower part of the Grip is attached to by the friction of the legs) vs. upper plate of the Grip which is still stationary or rotating at a slower speed will cause the pads to move slightly inward on their spiral tracks to maintain the grip on your piece. With the direct drive electronically controlled motor of the Shimpo Whisper, when you take your foot off the pedal to stop, it stops so fast that the differential momentum between the top and bottom plates of the Grip reverses, the top plate keeps spinning slightly after the wheelhead stops, and the pads are moved slightly outward on their spiral tracks. Every other brand of wheel comes to a stop slowly enough that the friction between the top and bottom plates of the Grip keeps everything in place. @AlexX If your wheel turns counterclockwise for throwing, etc. , then the top plate of the Grip should rotate clockwise when the wheel is stopped to tighten the pads. Hold a finger against the side of the wheelhead to be certain it doesn't move, and turn the top plate of the Grip each way to see which direction causes the pads to move in and which direction causes them to move out. If they move inward with a clockwise turn, then you have the counterclockwise model. If they move inward with a counterclockwise turn, then you have the clockwise model. Yeah, that's a head spinner in more ways than one... The upper and lower plates of the Grip need to be rotating in opposite directions with respect to each other to tighten.

While waiting for your pictures, a kiln must be on a circuit that is 125% of the amperage of the kiln. Yours is 24 amps, so a 30 amp circuit is needed. The 8 ga. wire is more than enough. Leave it alone. Your kiln had a 50 amp plug. This is probably just a convenient coincidence, as that is what larger kilns use, so perhaps they just built them all with the same power cord, less inventory to keep on hand in the factory. It doesn't need to be 50, but that's what was there. You've already cut it off, so you are stuck with that. It would have been easier to change the outlet on the wall for one that fits the plug, but you are where you are so put the plug on the power cord. Your picture of the circuit breaker for the kiln is cut off, can't see the numbers on it. Note that on 240V double pole breakers, the number on the handle is for each side of the circuit, but they do not add together, i.e, if the numbers are both 30, it is 30, not 30+30=60. However, If it is truly a 60A breaker (both numbers are 60), that is dangerous. The kiln only needs 30, the 8 ga. wire is only good for 40, but the breaker won't blow until a 60A error occurs, at which time the kiln will already be fried and the wiring on fire (that's a bit of an exaggeration, but don't have a larger breaker than the wire can handle or significantly larger than the kiln draws even if the wire is ok at the higher amperage). However, it is ok to have a smaller breaker than the wire size, just not the other way. So, change that breaker to a 30A and your kiln will be good to go.

Ha. For some, this glaze chem stuff IS wilderness camping. All. The. Time.

This is an interesting and useful discussion. I too have noticed the top and bottom sections "working" harder than the middle, but didn't put it together the way you just did. I wonder if this is where Skutt gets it by putting hotter elements at top and bottom? If one paid extra for a Skutt with 3-zone control and the touchscreen, would the data dump show the top and bottom sections at lower percentages, closer to the middle section to maintain even temperature?

This may be a bit geeky for the average artist, but with the Genesis controller, you can extract a data file for each of the last 10 firings that lists the setpoints, actual temperatures, and percent of power-on time every 30 seconds. Import that into a spreadsheet like Excel and calculate rates of temperature rise at various stages of the firing and for each section of the kiln. If you are facile with the spreadsheet, you can construct graphics of programmed vs. actual. Like I said, it's a geek's toy, but it can be useful to see where the variances are from expected in the programming and imbalances between the sections. This is particularly useful when elements begin to wear and the ramp rates at higher temperatures begin to significantly lag the program. You can see how the run up to bisque seems to be normal while glaze firings go on forever until the dreaded E1. I've also used this by setting a high ramp rate for a long cooling segment down from peak (set it to over 400F/hr) just to keep the controller from turning the elements on at all while logging the natural cooling rate of the kiln. I doubt you'll find a brand new kiln to be generally lagging the expected program, but it can help diagnose section imbalances that can be tweaked with a thermocouple offset.

This has been discussed before. The main supplier of talc in the US is (was) AM-TAL, in Texas. For better or worse, Daltile, the big wall and floor tile maker uses so much talc in their production that it made business sense for them to just buy the whole mine a few years ago. Recently, they made another business decision to end outside distribution of the talc as of this month, only producing for internal use now. Yup, there is going to be some disruption. There are some other smaller talc mines, but it will be awhile for the market and distribution to settle.

@neilestrickSince we are on the topic of offsets and Morgan mentioned cone offset, could you expand on your experience with individual cone offsets vs universal TC offset? I get how the offset allows one to calibrate the controller's expectation of precision to the reality of the thermocouple's relative imprecision. But why would one adjust the offset in just one cone-fire value? If the TC is off by the 10 degrees in your example for Morgan, wouldn't it be off by 10 degrees, more or less, everywhere in the usual firing range? That would mean setting a cone offset for every cone in the controller. If I set 10 degrees in the offset for cone 6 because that's what fire my glazes to, cone 5 and 7, etc. are still whack should I decide to do a load of some different glaze at something other than cone 6? Or, is the TC offset variable across the firing range and some cone settings need more or less offset? That could be a challenge to test and dial in all of them.

What I was trying to do was use my logging pyrometer connected to the same thermocouple as the controller to keep track of what the controller was seeing/doing. I attached a separate wire directly at the thermocouple block. When I noticed the readings bouncing around, I gave the thermocouple back to the controller rather than have the kiln load bolloxed.