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azjoe last won the day on August 8 2011

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  1. I have yet to find a one-size fits all clear for cone 5-6 ox. I've had reasonable success with MS-29 clear bright (one of the Morracan Sand series). It's high gloss and works best applied very thin. That said, I have seen some crazing on WS4 clay and some yellowing on Dark Brown (Laguna clays)... so buy a pint of the pre-mix and make some test tiles to assure good fit and color for your particular needs.
  2. Normally the yard art I make has a rebar pole in the middle which is driven into the ground as far as needed for the ground characteristics at the site. You picture leads me to believe that the center holes don't necessarily line up, so rebar might not work in your case. I sometimes use JB-Weld (a 2-part epoxy) to "glue" pieces together... if attaching glazed pieces I rough up the glaze area where the JB-Weld touches to ensure better adhesion. You can get JB-Weld in most hardware stores and auto parts stores. There are several varieties of JB-Weld... I use the "original cold weld formula", usually the black color (which is really dark gray, not black). Like most good adhesives, the ceramic will break before theepoxy.
  3. Moroccan Sand glaze ?

    If you search long enough on the Laguna site you'll find some mixing guidance.... as I recall they spec the desirable density as something like 46 for clear glazes, 55 for dipping, 60 for spraying, and 65 for brushing. FWIW, in our facility we mix MS29 clear to 47 and most everything else to 55.
  4. error 1 message

    Bummer for the student. As I recall, Error 1 means the temp couldn't be raised 150-deg/hr as sampled by the thermocouple. Thermocouple accuracy drifts slowly over time, but during the course of a single firing they generally work or not... so I wouldn't assign very high probability to a thermocouple problem. That leaves sagging line voltage, a colder than normal environment, and aging elements or relays with a high contact resistance... or perhaps a "perfect storm" of degradations of all three. When you say "cold snap" was the kiln room temp still within spec. for the kiln? If so, then it may have been a factor, but isn't the smoking gun. When you say "voltage fluctuations" are you saying lights dimming for long periods of time, just flickering, or what? Generally the electric utilities will shut down lines of the voltage sags more than a few percent for more than a few cycles, so again, while it could be a factor, I doubt it's the smoking gun either. That leaves the wiring, elements and relays. Have you made actual resistance measurements on the elements to insure they are each within spec. for your model/voltage/phase kiln? Elements degrade with age (actually, number of firings) and it's not unheard of to find the wrong element got installed during a maintenance operation. Next would be checks for loose connections in the wiring that connects the controller to the elements? Next I would suspect the relays... I measure the current in the wires between the controller and the elements... if below spec then I replace the relays. I usually do all these measurements with my own test meters even though the newer controllers have some measurement features built in... old habits die hard, LOL. The 1227 is a pretty resilient kiln in my experience. My bet would be it's an element problem... probably age degradation which probably lead to a "perfect story" scenario... sagging voltage, cold near the lower limit of the spec, element resistance near the spec limit, perhaps even relay contact resistance near their spec limit... all at the same time... and bingo... Error 1. Element problems are not always obvious. I got involved in an odd Error 1 case last year for a friend. Her kiln had been re-bricked and new elements installed about a year prior to when it started the Error 1 failures. She said "everything was working ok... all the elements heat up and I've replaced the thermocouple... the service guy says I need a new kiln". That's like a red flag in the face of a bull for me since everything in a kiln is replaceable. The errors occurred during both cone 04 and cone 5 firings. When I checked the resistance of the elements they all looked reasonable and when I checked the charts they matched ... until I checked the charts again... they matched the wrong readings for her kiln's voltage/phase! A quick calculation showed they were putting out only about 2/3rds of spec'ed watts. Apparently, over the course of a year's worth of firings, the elements had degraded enough so that they became marginal in their ability to raise the temp 150-deg/hour.
  5. Help me, Glaze gurus!

    Thanks Bruce... just the info I was looking for. We use a wide variety of Laguna clays.... dark & med browns, reds, and whites fired to ^5. Sounds like it's worth picking up a pound of soda spar for a test batch the next time I buy chemicals.
  6. Glaze Calculator

    I think the first questions that need answers are 1)what do you intend to use the program for and 2)how knowledgeable are you in understanding glaze technology?
  7. Help me, Glaze gurus!

    Just curious... in your experience does this clear work with most clays and over other glazes, or are there some know "sensitivities" (eg, color changes, crazing on certain clays, other glaze interactions, etc.). Certainly I'd test for my particulars, but I don't have soda spar on hand and there's no use purchasing some if there are known limitations which I might not want to accommodate... the last thing I need is another bucket of once used chemical. Like most clears, I assume a thin application gives best results?
  8. I guess it's unwise to say "never"... but I'd wager it's unlikely you'll see me using pinks and powder blues on my pots. They're just not me I'm afraid.
  9. Just like the items you "find" to texture your slab work, start looking for ones to use for thrown work. Anything you can press into a slab you can impress on the side of a thrown piece. I sometime whack a pot with a wooden meat tenderizer, or a slotted spoon... only your imagination limits you. After you investigate the "steve tool" (which I use a lot, btw) you'll discover that there are many items you can "find" to use in a similar manner. Eg, pie edge fluter, parts from kids toys, and many other round gear-like items with textures on their circumference. Just mount them in a handle (similar to how the steve tool works) and hold them lightly against the pot while it's spinning slowly on the wheel. Gary Beck showed me one of his favorites... sharpener gears from an old pencil sharpener. They look like helix's, but when you hold them against a turnign pot them make a nice slanted patterns... one creates / / / / / / / / as it's pattern, the other makes the compliment \ \ \ \ \ . Of course, you can also buy texture wheels from your ceramic supplier, too. As others have said, there's lots of ideas on YouTube.... eg, some of the "chattering" decoration videos ("hsinchuen" has a number of them... I particularly like this one . He has others, one of which shows how to make a chattering tool from a hacksaw blade). Enjoy the journey!
  10. As offcenter said, it's just drying. Accelerated drying can work successfully for "pots" which are relatively uniform in cross section and moisture content. Whether it's in the kiln, in the kiln room, outdoors, etc. makes little difference provided you can control the rate of drying so the moisture gradient between the interior and exterior is small enough so that the shrinkage difference doesn't cause cracks. That's relatively controllable for the production potter who often has an entire kiln load of relatively similar thickness plates, bowls, cups, etc. It might not be as easy, however, when your kiln load consists of a varied lot of hand-built pieces, items with odd thickness as appended decorations, some sculptural pieces, etc. Most of us have mastered how to dry varied pieces successfully... some go under loose plastic, some under tightly wrapped plastic, some get thin appendages sprayed and rewrapped for weeks until the moisture content evens out, etc. Here in Arizona, it's often more of a chore to slow the drying process, not accelerate it... especially when it's 115 outdoors or the relative humidity has dropped to 4%. Personally, I don't use the kiln to force dry unless I'm really really pressed for time... and then only if the pieces are almost dry. I do, however, put pieces on shelves in the kiln room to accelerate their drying when I think they can take it... may as well put the heat that escapes the kilns to some use.
  11. Wow... there are so many... I never wedge 100 times, score/slip every joint, brush three coats of glaze, mix anything to the consistency of cream, compress every bottom and rim, etc. Over the years I've heard so many "rules" about so many things. Even when they make logical sense, I've never taken these "rules" to be strict mandates. To me, they're just guidance... an "if the show fits wear it" type of thing. As we gain experience most of us just seem to know, for example, whether we need to score and slip based on what we're doing and the condition of clay. OTOH, some "rules" do seem to be almost universal... captive air pockets are, in fact, usually a bad thing. If one never violates the "rules", how can one ever "push the envelope" to achieve something unique and special. My father had some sayings I pretty much live by when potting... "can't never did anything", "sometimes accidents are intentional", and "sometimes you win, sometimes you lose... and sometimes, you're rained out".
  12. Sammy, are your mugs sticking because of glaze running/sagging onto the shelf, or are they victims of the "plucking" situation someone else mentioned they were having? When I read your original post I assumed it was glaze running and the following comments pertain to that situation... First, I hope you're using witness cones (preferably on every shelf) when you fire so you know whether your kiln is actually firing to the temperature you think it is. Far too often people think they have a glaze problem, only to discover they have a kiln/firing problem... ie, a malfunctioning kiln sitter or thermocouple, a burned out or degraded element, hotter/cooler spots in the kiln, etc. Commercial glazes are usually tolerant of a one-cone variation, but that's not a universal truth for all situations. Second, different clays contain varying amounts of substances which can affect glazes dramatically (eg, color, running, etc.). For example, I recently fired a (new to me) commercial glaze on some b-mix and speckled buff test tiles... the result was a beautiful translucent blue on b-mix and a mediocre green on the speckle buff. It sagged on the b-mix and ran on the speckled buff. While overlaps smoothed out nicely, the color differences where overlapped was VERY noticeable on both tiles... hence, pouring/brushing the glaze could be problematic if one didn't want a somewhat "mottled" color effect. All in all, I concluded this glaze was problematic for my intended purposes but would make a very nice glaze for white clay functional ware that I dip. When you glaze fire there are many actions involved... the heat, the chemical reactions of the glaze, and the chemical reactions of the clay, etc. To some degree, they are interrelated, but not totally. If you are electric firing using commercial glazes, for a given clay you can only control the heat and the thickness of the glaze(s). Layering one glaze on another can make a stable glaze run due to the chemical reactions between glazes and/or the added glaze thickness... we often use this to our advantage to produce attractive visual effects in our glaze work. Lastly, I assume you're clear on the use of wax, but if not... wax is used to mask the foot of the piece when you glaze so that there is no glaze in that area when you fire. Any specks of glaze which "stick" to the wax must be wiped away before firing. Wax does not prevent glaze from "running" during the firing process... wax vaporizes and is long gone at a much lower temperature than the temperature at which the glaze melts and the clay vitrifies. Depending on how much your glaze "moves" (ie, sags, runs) at the temperature you fire will determine how much of the foot of your piece you need to leave unglazed... some glazes need only an eighth-inch, others a quarter-inch, and some more... sometimes several inches. I wouldn't fiddle too much with the firing temperature unless you've confirmed via witness cones you're firing too hot. Since you are making mugs (functional ware) it is best if you fire your clay to it's vitreous state... ie, to the cone rating the clay manufacturer specified (you said 5-6, so 6 is where it probably reaches it most vitreous state). This is important because any glaze defect (an imperceptible pinhole or crack, for example) on the inside of the mug will let liquids come in contact with the bare clay and be absorbed. For example, suppose your customer uses the mug for soup... meat juices might be absorbed and become a potential spot for bacterial growth. The more vitreous the fired clay, the less liquid is absorbed... for functional ware it's best to use clays with absorption specs of 1.5% or less, the lower the better. Don't go overboard worrying about this... just know the risks so you can choose your clays, glazes, and techniques to be as compatible as the situation allows.
  13. My favorite "stage" is when I'm working on a new idea/vision/inspiration... particularly when it's not straightforward how to construct/implement my vision. It's the period when I'm most creative... it's the time I give myself to play and have fun with clay, tools, techniques, and glazes, to experiment and refine/expand my capabilities. For me, it's the time when I feel I'm creating art... something unique. Even when the result is a failure, I'm inspired by what I've learned, and often with some aspect of what I've created. Honestly, it doesn't matter a whole lot whether the clay is still in the bag, leather-hard, or I'm loading the glazed piece into the kiln... it's all part of the experience and each "stage" offers a wealth of opportunity to try new things that I can't afford to do when I'm doing production work.
  14. One trick to help glaze adhere to already-fired glaze is to spray the piece with a light coat of ordinary hairspray... no need for anything fancy, get the inexpensive stuff you can buy at the dollar store. It's basically lacquer. The aerosol can works better than the hand pump because the droplet size is finer. Anyway, it provides enough "texture" for the glaze to adhere to until it's fired (the hairspray burns off during firing). I've also read that spray starch used for ironing works too, but I've never tried that since in my house nothing gets ironed.
  15. Most commercial "ready to use" glazes say they are formulated for brushing. This makes some sense since a pint jar isn't big enough to dip most pottery, nor is there room to add water. Nevertheless, in my own work, I usually prefer to use commercial glazes thinned somewhat... I've alwasy used water with good results. Ultimately, you need to "play" with a glaze to really get to know it. Some glazes just do not give good results when brushed because of their ingredients... out of the jar they glob, add a little too much water and they don't cover well. Glaze "thickness" isn't the only variable... clay (both color and "coarseness"), decorative textures (particularly the sharpness of edges), layering of multiple glazes, your kiln/firing schedule, etc. all affect the end result. Some glazes are pretty "finicky"... others produce good results across a wide range of conditions. When investigating a new glaze I always like to fire some test tiles first... this lets me know how thickness affects results, whether the glaze sags or runs, what the glaze color will be on my clay, etc. Test tiles are easy to make... I texture one side , leave the other side smooth. Typically I dip my pieces, so I dip a tile 3/4 of the way in for a count of 2, let it dry then dip it in again to 1/2 for a 1-count, let dry and then dip again 1/4 in for a 1-count... now I have a single tile with three different thicknesses of glaze. If none come out the way I expected, then I try adjusting more or perhaps the firing schedule. I keep notes about what I've done so I can replicate the process in the future. (If I were going to brush the glaze I'd brush it on the test tile... two coats, three coats, 4 coats). Typically you want the glaze thickest when dipping, a little thinner for pouring, and still thinner for brushing (since you want to apply multiple coats for even coverage). Laguna recommends, for example, that their dry glazes be mixed to the following specific gravities: (Baume scale) 55 for dipping, 47 for pouring, 43 for brushing. I know you're talking about Amaco PC glazes, but the same should hold true I think. I assume they package Ancient Jasper as thick as they do because they want you to apply it really thick... the developer of the glaze suggests 4-coats ( See this discussion ). A good rule of thumb to start with is you want the glaze layer on the bisque to be about the thickness of a credit card when you're ready to fire. Many glazes have much different needs, however... eg, Ancient Jasper more thickly, clear glazes typically thinner. The glaze mixture needs to be thin enough (ie, contain enough water) so it flows (instead of globing up) when brushed, or thin enough so it deposits the right thickness when dipped for 3 seconds (or whatever time you dip for), or thin enough so it adds the correct thickness when poured. That's why you need to "play" a little so you know cause and effect of variations to get the results you want/expect using the methods that are right for your situation and experience.