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joshur

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  1. Yes the tube is open on both ends, one end cut off and cut to length at the same time, they are very hard to cut, nick or score the tube with a diamond blade.
  2. Joe, look at some of the pictures I posted, you can see the sensor, the box it came in and the part number on the box, a new sensor is about $25-$40 at the discount auto parts stores, if you are in doubt about the accuracy of the one you have. Also for one thing the reading does not start until the kiln gets up to about 1500F then you will see the reading climb with the rise in temp, that is if you are in reduction. You can see in another picture of the meter that the reading in heavy reduction at about cone 10 is 900mV, I try to keep the reading in the 500mV to 700mV range for most of the reduction portion of the firing.
  3. Chris, Did you get your question answered about how to apply polyurethane to a table?
  4. Here in the Pacific NW, there are lots of times it is so cool and damp that things will never dry. I built a cabinet around a set of wire shelves, and place a dehumidifier and a circulating fan in it along with my clay items. Works very well but has to have a small heater as well if it gets below about 65 degrees in the cabinet for the dehumidifier to work, it works so well I have to keep a close eye on it so it does not over dry things. I also use it for drying fruit and vegtables etc.
  5. Solar Powered Kiln?

    Sure you can, if you want to do it directly it will take 10 to 20KW or more of panels and the inverters that will run that much power, the problem with that other than the size of the system, is the sun is only out for so many hours each day and peak output time is even less. If you can be connected to the grid, it is much easier to do it with a Grid Tie System, that way you can have a much smaller system, and be putting power in to the grid when you do not need it, but can then use the grid power when you need more power to your kiln or other high current appliances, or if the sun is not out. I have a 7.2 kw grid tie system that I have been using this way for 12 years, works great. Another way is find a big old generator, if you are going to be totally off grid, a big generator is a great thing to have.
  6. Black Mountain Bisque

    My one experience with Black Mountain, was a failure for my application. It was the sculpture mix, hard to work with, came out of the bisque very porous, rough and spongy, but intact, but when high fired it came apart. As you can see from the picture, not only would it not hold a seam, but the body itself failed, never had another clay do that, needless to say I only tried it once.
  7. Stainless Steel In Kiln?

    You would be much better off making the handles, then gluing the stainless in after firing, the most common types of stainless steel 304 and 316 loose their ability to resist oxidization at about 1650F along with other changes to their basic properties, in the end you will not have the stainless you started with. Heating most alloys to high temperatures, requires special atmospheres and other conditions, and usually also requires the metal to be refinished and reworked even if the proper procedures have been followed, just for fun put a piece of your favorite stainless in your next firing and see what it does.
  8. Diy Kiln Vent

    I used aluminum dryer duct for for the exhaust pipe on the one I built, the condensate ate lots of holes right through it on the first firing, changed it out to galvanized steel vent pipe, no problems since. Yours looks like it might be the aluminised Mylar, and if the Mylar is on the inside it might not be a problem. Josh
  9. Compressor

    Rebbylicious, My recommendation on sprayers, is the gravity cup sprayer, pictures attached, they work very well for me, they are consistent easy to use and adjustable. The only thing is they must be cleaned between each use, not a big deal, just has to be done. They are the kind used for automotive, cabinetry and many other uses, and the anyone who has experience in these fields can instruct you in their use, as the method of use is similar for paint and glaze. http://www.harborfreight.com/20-oz-high-volume-low-pressure-gravity-feed-spray-gun-47016.html
  10. Compressor

    I think the best compressor for your needs would be a smaller belt drive portable model, such as this one, http://www.ebay.com/itm/CRAFTSMAN-3-horsepower-Air-Compressor-PICK-UP-ONLY-/221334253683?pt=LH_DefaultDomain_0&hash=item33888cb073 Here is a new one for comparison http://www.grainger.com/product/SPEEDAIRE-Air-Compressor-1NNF6 This type has been around a long time and companies like Sears sold millions of them, they are long lived and relatively quiet compared to a lot of the newer direct drive ones. Shop around on Craigslist, and check a few different ones out, listen to them to understand about the noise level and type of noise different ones produce. you should be able to find a good one for between $100. - $200. The two gauges are, one for the pressure in the tank, how much air you have, and the second one is to tell you what your spray pressure at the regulator is set at. And if it Is still too noisy , you can wheel it outside while you are spraying. Josh
  11. Results: First, a picture of the kiln and sensor in operation, this is right at the end of the firing, giving the kiln a short heavy reduction soak prior to shutdown. This kiln is probably 45 years old, it has an interior dimension of 37" x 37" x 42" and a stack area of 24" x 28" x 37" it uses about 30 gallons of propane for a cone 11 firing and takes 7 to 9 hours. Next are a couple pictures of my work at my current show at the Mendocino Art Center, Most all of these pieces were fired using this kiln and sensor and almost all this year. Josh
  12. Using the O2 sensor, One of the major advantages of the store bought sensor, is that it needs little or no maintenance, on the other hand, our home made version, should be cleaned and inspected prior to each use, turned on at a specific point, and closed up immediately upon shutting down the kiln. The first step to setting up the kiln to fire, is to clean the sensor and the intake pipe and chimney. Picture one shows the sensor in the storage mode, pic two shows the sensor after a firing, and three is the cleaning of the intake tube, it is best to clean the sensor and tube first as some debris, soot, spiders, etc. may be blown into the kiln, I use compressed air to clean the sensor, and tubes. The threads on the sensor are slightly smaller than the thread of the 1/2" iron pipe, so a couple wraps of aluminum foil on the sensor threads, takes care of this and makes the sensor easy to unscrew for cleaning, you could find a proper adapter, but the foil works fine for me. The sensor exhaust should be kept covered as pictured in #1 and the chimney not connected until the kiln is close to reaching the temperature for starting reduction, there are several reasons for this, one is both type of sensors, do not give accurate readings until they reach a certain temperature, but most importantly our sensor operates at lower temperatures than a internal sensor and during the kiln temp rise from start until it is at least 1000F there is moisture, soot and other stuff being given off by the kiln and this can condense on the sensor, and the temperature at the sensor may not be high enough to burn it clean. So, I clean the sensor, put it back in, close it up, clean and stack the kiln, then start the kiln. When the cone 011 guard cone for reduction starts to go down, I remove the cover, see picture 1, put on the chimney, pic 4, and hook up the meter, 5, at this point the kiln is warm enough to provide hot dry air to the sensor, and quickly heat the chimney to establish a good kiln gas flow past the sensor, carefully check that the chimney near the sensor is getting warm or hot to confirm a good flow of gas. The portion of the chimney pipe that is in the kiln exhaust, may get hot enough to glow red. When you turn the meter on at this point, you should start to see a gradual rise in the voltage, and by the time the kiln is hot enough to need reduction, the sensor assembly should be giving an accurate reading. This kiln is a little touchy on getting the gas air mix just right to get the reduction I want and sufficient temperature rise, but once set it requires little adjustment. With a sensor to establish the proper carbon monoxide level, you may not see some of the usual indicators of reduction, especially as the kiln gets hotter, such as smoke, soot on the peep plugs, and a cloudy or slightly obscured view of the ware through the peep, as the kiln should be operating more efficiently while still maintaining the required carbon monoxide level. As soon as I shut off the kiln I disconnect the chimney and cover the sensor exhaust to prevent outside air from going through the pipe into the kiln, for the usual reasons not to have an opening on the side of a hot kiln. Next: Results ,
  13. Jed, The readings from the sensor seem to be quite sensitive and cover a broad range, The attached chart shows what is going on with the readings you will see on the meter, the 0.1 to 0.8 readings on the left of the chart are volts, when the meter is set to read in the say 2 to 20 volt range, your reading in the reduction phase might look like 0.712 volts and drop down to 0.345 for a few seconds after opening a peep hole on an updraft that would draw in extra air. Even when the kiln is very stable the reading will bounce around 0.020 or 0.030 volts. These readings seem to be very similar using either the commercial kiln sensor or the automotive one, same with the meters, fancy or cheap have similar readings, in fact some of the commercial units just use a relabeled common multimeter, as a readout.
  14. The tricky part. Is to get a consistent flow of kiln gas to the sensor and at the proper temprature. As different kiln designs have very different air flow and internal pressure, the sensor assembly must be set up to the individual kiln. A down draft kiln that has enough back pressure/ positive pressure is the easiest to set up and operate, all you need to do is drill a hole in the kiln wall, about 3/4 of the way up the wall, twards the back of the kiln, and away from peep holes, you really do not need much flow by the sensor, but it must be consistent. The tougher one is the updraft kiln, the updraft is often operating in a negative pressure mode, not only that but the kiln air flowing past the ceramic tube on the inside of the kiln wants to pull air in through the tube from the outside of the kiln, like the venturi effect in a carburetor. I did two things to solve these problems on an updraft kiln, one was to create a gas catcher inside the kiln to assist in getting the flow in the right direction, the other is a long metal chiminey, heated by the exhaust from the kiln. The first two pictures are of the gas catcher, just a piece of soft brick that is partly hollowed out, then cemented and pinned over the intake end of the ceramic tube, to funnel the gas into the tube. The third picture is the sensor assembly on the kiln, the next two are the kiln with the sensor and chiminey pipe attached, and the last is just the chiminey pipe, which is just a section of 3/4" metal electric conduit that slips onto the metal pipe that comes out of the tee. The last picture is of the complete setup. Feel free to ask questions, or ask for more pictures if things are not clear. Next: Operating the sensor.
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