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Everything posted by CactusPots

  1. An interesting topic has come up (for me) in the liner glaze thread. Basically when a glazing or any other procedure is more practical for a production potter or a studio potter or a beginning or casual potter. A production potters goals are much different from either a studio potter or casual potter. I'm using the term studio potter to define myself. Lots of experience, but no interest in making lots of the same pot. A casual potter simply hasn't made enough pots at all. For this particular operation, a liner glaze in a mug or bowl with a sharp demarcation to the exterior glaze, the casual potter wants a relatively fool proof method that will give the best chance of success for a good percentage to come out as expected. No special skills required. Neither myself or casual potter is going to gear up for a 100 pot run. If there's a step in the procedure that guards against error, such as getting exterior glaze inside on the liner, it's worth it to both of us to wax the inside first. I assume the majority of persons who lurk on this forum are not production potters. I thought to write my steps for their benefit, as it took me quite a while to figure it out myself. It's definitely worthwhile to hear from the pros, I appreciate their input even if I can't always use it.
  2. If you glaze the inside of the pot with the blaster and then remove the top, I assume you are putting the not food safe glaze on the lip now? The object is liner glaze on the inside (and lip), super clean break and whatever glaze you like (shino, barium, much worse) on the outside. Not making a production run.
  3. Chances are you'll either get a holiday or an overlap. Unless you've done this 30k times and can now avoid that. The wax makes it picture perfect right out of the box. Worth the time, I say. The goal is the best possible result with the minimum talent/expertise/experience.
  4. Here's what I've worked out as the best way to do a food safe liner glaze with completely different exterior glaze. This is not for the production potters, too time consuming. You guys are going to find glaze combinations that don't require something like this. I'm pretty sure for this effect, this is the best method. Glaze the inside the usual way, pour the glaze in, roll it around as you pour it out. Holding the pot upside down, get 1/4 to 1/2 inch on the rim. When dry, scribe a line down from the rim, all the way through to the clay. Giffin Grip to the rescue. Easier to scribe a straight line than brush wax one. Using some sort of scraper, remove the glaze below the scribed line. I like a Xiem tool with a paddle head on one end. Using a rabbit ear sponge, clean it up and smooth out the bottom of the new glaze line. Wax inside and rim. Much easier to wax a raised glaze edge. Holding the pot from the inside, glaze the outside bottom first right to the wax line.
  5. I've learned a lot from the posts on this forum. I do think though, that never more than today, "how do you know this?" is always an appropriate question.
  6. Have you ever actually tried this as an experiment in practice or are you only talking theory? I'm not disputing what you are saying, just asking if you've ever set up a trial and measured results.
  7. I have a cut shelf for my damper. It has to be ridiculously uneven as the inside is getting direct blast and the outside 6-10 inches is exposed. Not the advancers, but the cheaper silicon carbide shelves. Have not seen a problem with this setup. I have a dozen or so firings on the only set of advancers that I have and I only use them on the top where the cooling is slowest. They are still perfect. So here's another question: are the advancers more sensitive to thermal differences than the standard silicon carbide? Except for the fact the SC shelves warp, they are just as good for glazes not sticking as the advancers. Yeah, the advancers are lighter also, but the warping is the big factor. I've heard that "if it aint broke" thing before, but it doesn't apply to me. I'm a diagnosed tweaker. Not the druggie kind.
  8. I've been operating my home designed and built 36 cf ceramic fiber downdraft for 20+ years under the premise that extra mass at the lower part of the kiln would make the kiln fire better. Primarily, I'm talking furniture. I have 1 inch mullite shelves on half inch posts over the kiln floor (2x k26 soft bricks) and then one set of 4 18x18 3/4 " shelves. The rest of the shelves are silicon carbide and advancer. What I'm thinking about is how necessary are the heavy shelves low in the kiln? Frankly, I'm tired of messing with kiln wash and would like to add 2 more sets of advancers. I guess the only way to know for sure is to try it, but theoretically speaking what do you think?
  9. It's definitely easier to finesse too soft clay than try to work (throw) with slightly too hard clay. Harder clay will let you more easily be aggressive with expanding, etc, but not really worth the pain. There are several good techniques for making commercial clay softer that are worthwhile.
  10. I was absolutely crying from arthritis in my fingers a year ago. Cortisone injections were sent from God. Unbelievable difference. Everyone is different and this may not help you, but I was almost in despair. Still like hot water in the throwing bowl.
  11. I'm not that good at throwing even after 25 years, so I use this cheat. Using 2 ribs instead of your fingers will even out the clay. This is really nice as the final touch to remove throwing marks. Assuming of course that you don't want them. Sometimes I do this with another standard pull following, especially if I've left too much clay at the bottom. I use the next smallest Sherril blue ones for this.
  12. New clay bag---> collect clay scaps and slag---> pug and age clay---> throw away. I usually cut the clay bag to take the really wet clay out for the pug mill, so it's done at that point. Pretty good to get three uses out of one original. I'm at least 30 bags ahead at this point, so that's good.
  13. Once again, I make a comment thinking gas kiln and everyone else is talking electric kiln. How anachronistic I am.
  14. But does that get you a dead sharp line between the glazes? Or does the "play well" part mean the overlap looks ok?
  15. 2 disagreements with this statement. First, the reference to "functional ware". Kitchenware or food ware would be more accurate as (for instance) my planters are as functional as your bowls and mugs. Second, (imo) when potters use the term "liner glazed", they're assuming a different glaze on the outside that is not intended to contact food. If you glazed the entire piece with a standard food safe glaze, you wouldn't refer to it as a liner glaze. The intent of the exercise is to use a wider range of glazes than would be allowable with a single application approach. The first one actually bugs me since potters making planters seem to be held in lower esteem (imo).
  16. I'm guessing the production potters here don't use liner glazes. The reason for my thinking is that I don't know a way to make a clean transition between the inside glaze and the outside glaze that isn't just very time consuming. I'm doing it with latex resist, 1st glaze, wax resist, then second glaze. It looks good and I don't do kitchen ware very often, so not really a big deal for me. I guess the other option would be an overlap on the outside that worked between the 2 glazes. Not going to happen with a shino or a lot of glazes.
  17. Off the website: Variable Speed Control: Optional Mine never sounds like it down shifts. Same old granny gear all the time.
  18. Shop vac takes care of the dust. Or a big ass fan outside. I did build "flaps" initially when I built the kiln. It was a tin box, maybe 6" x 6" filled with ceramic fiber, The bottom one is still in service, but the top one burned out a while ago. Hence the plug.
  19. Pretty sure mine doesn't. Just start, stop, pug and vacuum on the control. I can see where it would be useful. Maybe the doc you're looking at is a new upgrade model.
  20. I used Peter King clay. Not the easiest to throw, but they have held up well so far (maybe 60 cone 10 firings). You could maybe just use Soldate 30 or add a bunch of grog to a basic cone 10 white or light colored clay. I think if I was to do it again, I'd extrude the spy holes square and fit a square tapered soft brick plug. Making a mold form for castable would be tricky. I don't think it would be durable unless it was pretty thick. I used castable cement for my exhaust damper box. At least one piece cracked, but is still functionable.
  21. I don't think my PP VPM 30 has a speed control.
  22. What kind of pugmill has speed adjustment?
  23. Or taking a fresh bag of clay and running it through the pugmill. I've not tried this, but I suspect if it was hand building firm and not throwing soft, it would come out short(er). The process SBSOSO is talking about dries the clay significantly by the time it gets back into the pugmill. It's an interesting question why they were able to get away with immediate use after pugging scrap and now they can't. Lots of ins, lots of outs and lots of what have yous.
  24. I noticed the exact same problem with my reclaim clay. I called Laguna and asked their clay "expert" about it. Their reply was that the commercial pug mill they use has so much more powerful vacuum that my Peter Pugger. I don't know if I fully buy their explanation, but I don't have a better one. The working solution I'm using is to pug wet and age. Very nice clay that way. I think Sorce may be on to it. By the time I get around to a session with the pug mill, the scrap has been sitting in bags wet for quite a while. Sometimes even a touch of green. It's definitely not short coming out of the pugmill now, but it's really soft and needs to age to be ready to use.
  25. I think this is the right approach. I don't know where the math failure is here, but half a bag of clay will not give you a 30x30x 1/4" slab, just from experience estimate. I don't know why Min's calculation is off. The pug is a little smaller than 12x6x6 to actually measure it, Not by that much (half). The rough calculation of 432 cubic inches by 25 pounds is 0.05 lbs per cubic inch. I rolled out a 1/4" slab and cut it to 12"x 12" and it weighed 4 lbs almost exactly. That comes out to 0.11 lbs per cubic inch. This seems to work for my calculation and gives me a better way to estimate what I need. 30x30x .25= 225 x .11= 24.75 A whole bag.
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