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Dick White

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Everything posted by Dick White

  1. Dick White

    Pressure gauge reading

    It is useful to understand the physical process going on inside the tank. Propane is more precisely LPG, liquified petroleum gas. The gas is pumped into the tank under very high pressure, and in accordance with the Ideal Gas Law from your high school chemistry class (PV=NRT), the gas condenses into liquid - so long as it remains under pressure in the tank. As you release the pressure in the tank by opening the valve, the liquified gas evaporates from the top of the pool in the tank and escapes out the valve (and then travels down the line to the burner). Simultaneously, as discussed in another high school chemistry lecture, an evaporating liquid takes thermal energy with it during the phase change from liquid to gas, leaving the surface from which it evaporated colder. In our nearly closed system where liquid, gas, pressure, and temperature of the LPG are in tight balance, the cooling effect of the evaporation can cause the phase change to reverse, i.e, the LPG will freeze instead of continuing to evaporate. The faster you draw off the propane, the faster it must evaporate from the surface of the liquid inside the tank, and thus the faster it will freeze instead of evaporate, causing the burner to go out. There are two solutions: 1) You can provide external (relative) warmth to the bottle by pouring water over it or setting the tank in a tub of water; or 2) You can increase the surface area of the pool of liquid so that the rate of evaporation (as determined by your usage of gas at the burner) per unit of surface area in the tank is lower, thus reducing the speed at which the balance tips into freezing, or preferably, eliminating the tank freeze. This second solution is achieved by using a tank with a larger diameter (up to and including the very large tanks that sit sideways, but a taller tank of the same diameter is ineffective as the surface area of the pool of liquid is unchanged) or by linking together multiple tanks through a manifold (which could be a simple Y connection between 2 tanks) so that the rate of evaporation from the combined tank surface areas does not result in the tanks freezing. And so, beyond understanding the process going on inside the tank, I will leave the hardware specifics (regulators, connectors, valves, and safety systems) to Mr. Ward's recommendations.
  2. Dick White

    New Kiln test

    An empty kiln requires very little energy to heat just the air. Air heats very quickly. The only real value to firing an empty kiln is to either condition and temper new elements when they are replaced, or to determine if it will turn on at all. If you want to know how it will perform with the thermal mass of wares in the kiln, then you need to fill it with wares.
  3. Dick White

    Measuring pot bottoms

    I think the challenge in the question is how to determine the thickness of the leatherhard base before trimming without leaving a destructive hole through the bottom of the vessel (that will later leak, or at a minimum, require effort to repair).
  4. Dick White

    Glaze Ingredient Storage

    For a tall narrow container, consider something designed to store rolls of holiday wrapping paper.
  5. Dick White

    Most used sieve size?

    I have a 30 mesh sieve that I use occasionally for really lumpy glazes, or to resieve a hardpanned glaze. It breaks up the clumps and everything passes through quickly in far less time than I would need to scrape it directly through the 80 mesh screen.
  6. Dick White

    Engobe for decorative use on bisque

    Yes, clear glaze over colored engobes, slips, and underglaze patterns is quite common. Whether it will be smooth in the end is a function of the smothness of the application of the engobe.
  7. Not to be a stick in the mud (very very bad pun, naughty boy, go to your room and don't come out until you have picked up all your toys...) but a concern with the stick (or whatever) in the blob of clay on the edge of the splash pan is that if you are going to do a long production run over a considerable length of time, the clay will begin to dry and shrink, and the pointer end of the stick will move. The movement will be imperceptible from piece to piece, but the size of the last piece of the day will not be the same as the first. If you don't mind spending a bit more than a trip you your favorite coffee shop to snitch some extra stirring stick Hsin-Chuen Lin (of UBoob video fame) markets a metal adjustable tombo gauge with measured markings and an alternate configuration of the tool to measure the thickness of the bottom of your pot before you trim (so you know exactly who deep you can trim your footring).
  8. Dick White

    Older Bailey Slab Roller value?

    Does it click when you roll it? If it clicks, there is a ratchet and pawl somewhere. Is the big hand wheel screwed on its shaft by left hand thread, i.e., it advances the clay through the roller (left to right) by turning the hand wheel counterclockwise? If so, when you turn the handwheel clockwise, do the rollers turn or does the handwheel simply unscrew from the shaft? BTW, notice the red sign on top with the big arrows point to the right. The label says it should go only that way.
  9. Dick White

    Older Bailey Slab Roller value?

    All have the chain and sprockets, the difference is where/how the handwheel and its drive shaft enter the drive train. And yes, you can smash any wad of clay in one pass with this beast, but IMO you shouldn't. Rolling a slab stretches it in the direction of the roll. Clay memory will cause it to later shrink back more in that direction. So, a slab rolled in one smash and then cut to a perfect square/circle will end up as a rectangle/oval. A better technique is multiple rolls in multiple directions. You can't really do it like the manual rolling pin brigade, flipping it and turning it and rolling every which way. Here you have to roll in increments, and turn (and flip) the developing slab as you bring it down in thickness. That also means picking it up from the output table and bringing it back around to the input table, and doing some mental gymnastics along the way so it doesn't get so long during an interim pass that you can't turn it and still fit it within the width of the roller for the next pass. In the video, that was a nice parlor trick Mr. Bailey showed us, rolling a perfect slab the exact length and width of the table in one roll, but the kiln gods are waiting for a smackdown on that with some uneven shrinkage.
  10. Dick White

    Older Bailey Slab Roller value?

    Yes, that's Mr. Bailey himself. We have 2 of them in studios I work in. One is way-old, the other brand new last year. And yes, they must be rolled from left to right ONLY! On the older model, the hand wheel turns clockwise, and the slab moves as if the rotation of the hand wheel is pushing it through. There is a ratchet and pawl on the lower roller that prevents you from turning the wheel backwards. Unless you force it and bend the pawl pivot (which students have done several times over the years, then you have to disassemble it and repair the pawl, until it breaks and then you must buy a new one, $32, don't ask how I know the price...). On the new model, the wheel turns counterclockwise, visually contrary to the motion of the slab, but you get used to it - pull back on the wheel to make the slab go forward. There is still a pawl and ratchet on the lower roller, but now you can't turn the roller the wrong way by turning the wheel backwards. Now the handwheel is threaded (left hand thread, to be exact) onto the drive shaft rather than affixed by a set screw on a flat of the shaft. Thus, if you turn the wheel the wrong way, it will simply unscrew itself (and if you turn it enough times hoping it will finally draw the slab backwards, the wheel will fall off and break your toe. Lesson learned yet?)
  11. Dick White

    Celadon - Application?

    Alice, I will refrain from getting you started on the commercial "celadons" if you will excuse me for starting a similar rant about the line of "shinos" from that other commercial purveyor...
  12. Dick White

    Skull E-1 error question

    E-1 is failure of the temperature to rise. If the room temperature got to hot for the controller board to function properly, the error would be E-bd. The most common cause for an E-1 error is worn elements. The amount of power needed to raise the temperature in the kiln increases as the temperature goes up. It doesn't take much heating power (relatively speaking) to get to bisque/low fire temps. But it takes progressively more heating power input to get each degree of increase. Thus, you can run a kiln for bisque/low fire only forever, but it will fail if you try to take it much higher. You can check the resistance of the elements with an ohm meter. A second cause could be that one element is broken. A good kiln like Skutt can reach bisque/low fire temperatures with one element out. But then, as with worn elements, it just can't go any farther. Another cause could be a relay stuck in the off position. The controller is telling the relay to turn the elements on, but it's stuck and doesn't, so the kiln doesn't heat. That can be more difficult to diagnose as it might be intermittent. Check the elements first.
  13. Some practical considerations regarding kiln wash: Wash only the top side of a shelf. The bottom side of the shelf should be bare clean shelf so that chips of wash do not fall off into the glazed work on the shelf below. This also means you cannot randomly flip your shelves in the hopes of evening out warpage. If you wish to flip a shelf, you'll need to clean off all old wash from what will now be the underside of the shelf. When you apply the wash, keep it 1/2" or so away from the edge and do not let any dribble over onto the edge of the shelf. Those little drips will get knocked loose while handling the shelf during loading and will, like chips from the underside (see above) inevitably fall onto a piece below. Use a wash recipe that is known to be solid and not peel and flake off. My preference is 50% alumina hydrate, 25% kaolin, 25% calcined kaolin. Some also add 1% feldspar just to help it fuse to the shelf better, but I haven't needed that. dw
  14. Dick White

    a quick question about Process

    Magic water is a very mild deflocculating solution that seems to open up the surfaces to be joined by the same process of creating similar (and consequently repelling) ionic polarity of the clay particles, thus allowing the joining surfaces to intermingle better. Deflocculated slips have two characteristics of interest - 1) obviously a deflocculant is involved, similar to magic water, and 2) the deflocculation allows a lot more clay to be incorporated into the same volume of slip, making for a stronger and drier (less shrinkage) joint. Vinegar, a mild acetic acid promotes adhesion between the surfaces of the parts to be joined. Which is better depends on who you ask. I take it a step further by using a paper clay slip made with vinegar rather than water. Plain water and the paper fibers will quickly turn to black mold if kept in the wet state, but vinegar instead of water will effectively pickle the paper fibers so you can keep a tub of it ready to immediately use as needed. And the vinegar does double duty for adhesion.
  15. Dick White

    Re-firing low fire glaze

    If you are using commercial brushing glazes, the brushing agent that makes them brush out smoothly is usually an organic gum (CMC). That also will help the glaze to stick to a previously fired glaze surface. You probably don't need the hairspray trick. That's typically for dipping glazes.
  16. Dick White

    Dry wood ash on glazes

    I never tried it with other glazes. It works well with shino, didn't take it further. Maybe something to try? The Simon Leach method of wetting the ash will take you in the direction of washed ash (there is a whole body of knowledge with washed vs. unwashed ash in ash glazes) and the atomizer will give you a finer distribution of the ash on the side of the ware. And the blue spot is just a finger touch of blue glaze for visual interest.
  17. Dick White

    Dry wood ash on glazes

    No, sadly only 10. My shipment from from Dune was hijacked. And besides, like Custer, it ain't what it used to be, so I had to reformulate it.
  18. Dick White

    Dry wood ash on glazes

    I don't have my photo cube set up, so here is a thumbnail sketch...
  19. Dick White

    Kiln firing variations

    I have heard (but with no scientific proof offered, as I learned of this during a BOGSAT (bunch of guys sitting around talking)) that on a rainy day the water molecules in the ambient humidity are cracked by the intense heat and release some additional energy, whether from the broken molecular bonds or from additional combustion from the now-free hydrogen. FWIW, YMMV. dw
  20. Dick White

    Dry wood ash on glazes

    I frequently sprinkle ash on the side of mugs glazed in shino. I have a small tub of ordinary unwashed fireplace ash (mixed hardwoods, no pine, pine makes a lousy fire and gunks up the chimney flue) that has been dry seived to 80 mesh, which I use to refill an old spice shaker jar that I keep by the glazing table. When glazing the mugs in shino, I immediately hold the wet glazed mug sideways and shake on a patch of "special spice" ash.
  21. Dick White

    Terra Sig question

    A technical question for the terra sig cognoscenti here. Generalized background (nothing new here, just setting up the question to follow): T.S. is made by mixing some clay with an amount of water and adding some deflocculant to cause the clay particles to begin settling out. The larger particles will settle first and the finer particles will remain suspended longer. After a time, the upper part of the suspension with the finer particles is decanted as the T.S., and the sludge at the bottom consisting of the larger, settled particles is tossed out. Issue: As the decanted T.S. rests in its storage container awaiting its next use, it continues to settle out with a much thinner layer of sludgey clay on the bottom of the jar. Question: Would it be appropriate to reflocculate the finished T.S. to retard the further settling of the clay during storage? Would this change the working properties/procedures in any material way? Thanks for all your wisdom and insight? dw
  22. Dick White

    Terra Sig question

    Thanks. Since I have a gallon of it to work with, I will try a drop of vinegar in a half cup of it and see what happens. Watch this space, more to follow... dw
  23. Dick White

    Terra Sig question

    Thanks Magnolia, I am familiar with Vince Pitelka's T.S. page, and have been using that recipe for a number of years now. Here is the practical basis for my questions. My community studio will be having a naked raku workshop/firing in about 2 months, led by the inestimable Ray Bogle. In preparation for that day of fun and games, I made a large batch of OM4 T.S. for the general use of the studio members, resulting in about a gallon of finished sig. I've divided it into several jars, some will be colored with various stains or oxides, others will be left plain white. All are continuing to settle, with the thin layer of sludge sometimes being difficult to stir back up into the T.S. without remaining lumpy. And in the stained ones, the stain drops out first (as expected) but then becomes trapped by the overlying layer of new sludge. Also, if the specific gravity was correct (and yes, I too like 1.15 for this OM4 sig) and some portion of the solids settles out and is not thoroughly scraped up by a less-fastidious student, then the S.G. of the remaining sig will be lower, possibly too watery. Because this will be an intermittent and on-going activity for a few more weeks, I can't do the dry storage technique, so I am wondering if refloccing it with a dash of epsom or vinegar as we do with glazes will keep things floating longer without simultaneously causing the sig itself to become unworkable?
  24. Dick White

    HELP - bartlett v6-cf Won't hold temp

    The 9999 instruction is supposed to cause the controller to go flat out in whatever direction is next. 9999 in a heating ramp is full power on, raise the temperature as fast as the kiln's elements can generate heat. 9999 in a cooling ramp is everything off, crash cool as fast as the kiln can radiate it out. However, I have heard scattered reports that sometimes the controller might react incorrectly to a 9999 instruction. I don't know the explicit conditions or whether it is just some peculiar malfunction of a faulty device. Your report of the 9999->5555 issue suggests a controller fault of some sort, possibly only a minor one. Inasmuch as the 9999 command is "go as fast as you can," you might try a workaround by giving it a more specific ramp rate that in reality exceeds the probable physical capability of the kiln, and let the controller try to keep up. It won't keep up, but it will go as fast as it can. Try setting both of those 9999s at 300 or 400. It would take a very powerful kiln to heat that fast and a thin fiber kiln to cool that fast. I'm guessing that neither of those describe your kiln, so you will get the same effect as if you had programmed the all-purpose general command of go fastest. Another possible solution is try entering your program into a different User number. Maybe there is some corruption of a bit or two where that instruction is supposed to be loaded into memory?
  25. As Neil recommends, shut it off, it's not going anywhere new tonight. Also reconsider your notion that everything is 100%. If I were going to place a bet on one single item, I would bet that your elements are long overdue for replacement. That they have electrical continuity does not mean they are producing the designed amount of heat. Get a multimeter if you don't already have one and measure the resistance of each section at each switch setting, and compare to the specifications in the Skutt document at https://skutt.com/pdf/service_manual/11-5_ks_resistance.pdf As noted in the technical reference, if your measured resistance is more than 1.5 ohms over the spec, that will explain why the kiln never got to temperature.
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