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Everything posted by perkolator

  1. A lot of people come and ask me about used kilns they either see for sale or have been offered. Besides looking for the obvious things mentioned above, one of the most overlooked things I've noticed is that people don't pay attention to the power requirements and somehow end up looking at 3-phase kilns instead of 1-phase that most residential has. Yes, pretty much any kiln with a sitter can be converted to a digital control box.
  2. I have no science behind this, but if you're crash cooling at the top end of your temp you're going to end up pulling in significantly cooler air through your peep holes - could possibly thermally shock hot elements and brick local to the peeps. I do it because I already know I'll be working on my kilns continuously through the year, some home ceramicists might not ever touch their equipment until it breaks. Sometimes you just gotta do what you gotta do. I've been known to crash cool the student's work in a big gas kiln firing - just leave the damper and burner ports fully open and remov
  3. For crash cooling I usually let the students pull spy plugs below 600*. Crack the lid with a piece of soft brick when it's below maybe 400*. Fully open lids at 250* or lower and unload with gloves if need be. Typically leave vent on until room temp.
  4. For a damp box it likely won't make any difference since I'm assuming it's the type with just a slab of plaster. If it's slip casting molds then it likely would. I've always known regular gypsum plaster to be "weaker" than the Pottery #1. Your mold will degrade faster and won't hold the detail as long. I also think they have different absorption rates.
  5. You can use either Frit, Gerstley Borate, or make an underglaze with equal parts clay color and flux. Frits, being fired material usually leave a gritty/sandy texture to the wash, some people use CMC, laundry starch, karo syrup, etc to help. Usually I use GB and CMC gum solution, sometimes add a little bit of EPK in it too. Look up Linda Arbuckle's majolica notes, she's got a lot of suggestions for combos of washes. Most are by volume, not weight. Here ya go: http://lindaarbuckle.com/handouts/majolica-handout.pdf http://ceramicsweb.org/articles/arbucklemajolica.html
  6. since we essentially duplicate the process of forming rocks, all of our ceramics is permanent and will be here until it melts again with some great force of energy. maybe some sort of ultra hot explosion from warfare, volcano or lava flow, or perhaps heat from asteroid colliding with Earth. with that said, there is a lot of terrible ceramics out there that will be here forever.
  7. our students do this all the time with both commercial tile and dinnerware from thrift stores. simply use low-fire commercial glazes and underglazes. decals also work. definitely make sure you test fire the object at the temp you plan on firing to BEFORE you do your entire kiln full of them - sometimes we'll come across a random tile or plate that looks all good, only to find a puddle where it sat in the kiln. also, not all colors work with this technique - for example greens with chrome sometimes don't fuse well or flux out with the existing glaze
  8. aside from the foot itself, you will have to learn to use and control your glazes so you can get them close to the edge without them flowing past - test test test
  9. 10% is right about the starting point you want to use any mason stain in glazes, slips, clays, etc if you want to get the intended color.
  10. technically speaking clay can be VERY thick, you just have to fire it very slowly - think of a brick, those are 2.5" thick and they don't explode in the kiln. also, it's not just the preheat that needs attention to drive off physical water, you also need to fire very slow since the chemical water in your clay needs to escape the core of the work. lastly, there is down-firing involved with thick ceramics or your pieces will crack when cooling. i've got a decent amount of experience firing thick work - usually firings take 3-5days when you get into the 2" thick range for life-size sculpture.
  11. first thing i would do is figure out how to get those drains snaked because i'd bet that's half your problem. i'd even guess your custodial staff has one in their supplies as i've always know them to have at least one to test out before calling up a plumber and pay money. if not, you could rent one or better yet buy a cheap $10 25ft hand-crank snake from Harbor Freight (maybe even use a 20% off coupon since you can usually find a dozen in one Sunday paper) to keep in your classroom since this may be needed in the future. if your sink doesn't have one yet, look into either buying or fabri
  12. mortar and pestle? i would also try calcining it like suggested.
  13. pretty much any white slip recipe can be made into a colored slip. for most natural oxides you will use the same percentages you would in glaze recipe (so like 2% for cobalt carb = blue) if using a mason stain, you'll want to be up near 10%. my go-to basic white slip recipe is equal parts (25/25/25/25) of EPK, OM#4, Silica, and Custer Feld. you can easily tweak this recipe with flocculants/deflocculants or suspension agents to get the consistency you desire. this slip can be used at pretty much any temp range. for a raised slip/heavy surface texture, i prefer "Arnie's Fish Sauce" and
  14. wow, that's crazy! we've accidentally and purposefully fired coins in the kiln before, but never had any results like this. gonna have to do some experimenting!
  15. one of our faculty has a large AIM oval kiln that is over 15yrs old. she fires it all the time and never had any problems with it until a couple years ago when she burned through a couple sections of elements with glaze drips. to my knowledge, it's only had the elements replaced the one time (all of them), 2 relays, and one kiln sitter tube assembly - I would say that's a pretty good kiln. one thing I really like about the AIM is that it has clamping connectors for the elements instead of crimped like on a Skutt - I'm guessing it's slightly less efficient in terms of resistance, but sure is a
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