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  1. Charles

    Clay Additives

    Thanks for the info glazenerd. I thought granular feldspar fired to ^11 and higher produced the white rounded surface effect seen in Shigaraki ware - or is this what you mean by blisters? Granular feldspar fired to ^10 will produce pop-outs - as seen in this photo of Grogzilla. I became interested in coal slag after seeing Perry Haas' work. I've tried the small pellets used for commercial surface blasting work, and they just create small black specks when they are at the surface. I obtained some raw slag and broke it down to ~1/4" chunks - I just got a bisqued piece yesterday and immediately put it on the high-fire rack at school, unglazed as I wanted to see the surface result. I don't know if any of what I listed contains granular calcium, or if you are just drawing a comparison to feldspar. As far as firing sequence, I'm at the mercy of what the school uses, however from what you state as modern practice I'm sure they would do the hold. OTOH - since I'm exclusively interested in surface texture, I'm not aware of any reason I should be concerned about what happens on the interior of the piece? I may reduce the granite size to 6-10, but like them to look rocky.
  2. Charles

    Clay Additives

    It looks like all the posts so far are about glazes, but I have a question about clay. I'd like to create one or more clays with a lot of varied inclusions for visible texture. I just started making my own grog using a "dolly pot" small portable rock crusher, breaking up bisqued thin slabs of several clays and sorting them by mesh range. I decided I'm not interested in anything smaller than 40 mesh, as it just looks like dust to me. I do realize that commercial grog can be close to 10 times smaller. I gave my studio manager a list of my planned inclusions, and asked if he could come up with a recipe for the other 70%, preferably yielding a dark and rich brown. I saw an example of the color I'd ideally like, but believe I shouldn't attach other people's photos - I haven't actually checked site policy on this. Perhaps it's OK with accreditation. 1 % Ilmenite 1% small coal slag pellets ~1 mm 2% granular feldspar OR molochite - half each? 2% 6-10 mesh crushed granite 2% medium sand 2% large sand 10% 10-20 mesh homemade grog - ~ five mixed colors 10% 20-40 mesh homemade grog - ~ five mixed colors ------ 30% While he ponders this, I'm wondering about the possibility of adding this to wet clay? I realize the distribution wouldn't be as even as it would with dry clay, no matter how long I work at it. I want to try a test, and mostly wonder if anyone has done something similar, or am I crazy to even consider it?
  3. I've never used slip before, but wanted a small amount to experiment with. I tried cutting up some thin semi-wet clay (exposed for about an hour on the work table), putting it in a pint jar (Talenti) and filling it with water - expecting to need to let some of it evaporate later, and stirring. Two days later it hadn't really changed. I tried Magnolia Mud's upright (kitchen) blender approach in the school's glaze lab. It worked, but I didn't do my second batch - because: - It was an awful mess to clean up - I lost some slip that I couldn't scrape off / out of the blender - It took some time, as these blenders only stir material up to the top of the blades, so I had to stop, stir and push it down several times I decided to create a new batch for the second clay, and try a new approach. I rolled a thin slab, say 1/16" - 1/8" and let it dry for several hours, then cut it into roughly half-inch square pieces. No doubt drying overnight would be even better. I put this into a Talenti jar and added hot water to the top of the clay. Immediately the clay started dissolving, and I decided to pour off some water while the clay content was still quite low. I gave it a day to process, stirred, and it was ready to go. I'm sure the large mixers are better for big batches, but the hardest part of this process was dicing the clay after it had dried. A benefit is that the processing takes place in the same container that it will be stored in, so there is no waste and minimal clean-up . YMMV
  4. Charles

    Varied Perlite inclusion results

    Not necessarily "shardy", but with some texture and variation, as in the originally referenced piece. It was the texture that I responded to when I first saw the photo, as well as a bit of mystery, with a sense of possible hidden caverns. I'd be happy to go organic, but Rae expressed what interests me quite well. I've attached a detail image of Louise Gregg's piece that I found on her site. This makes it seem a very non-dense clay, almost more of a paper clay or similar. BTW - crushed walnut shells are used as an abrasive blast media (I looked at them online, but they appear quite boring), along with coal slag, which Perry Haas uses quite effectively in his work. I saw a comment somewhere that this works much better with porcelain, but doesn't do much of anything with stoneware. After looking for a source to buy a small amount from to experiment, the manager of a local sand blasting company gave me a pound of Black Beauty medium for free. I've used coffee grounds and they produce a very slight dimple where they were on the surface. Not at all dramatic, but might serve as background for a bolder texture. I've also tried Lapsang Souchang tea, which produces a pleasing surface texture, but very quickly grows a white beard when left under plastic ;-) I also like using mixed small chips of several clay bodies, or grog from them. Invariably some fall out while I work with the slab, but I consider the recesses part of the texture. I like using small pieces of granite, which I smash from chicken grit. In some parts of the country crushed oyster shells are the standard chicken grit, and I've heard of lesser rocks being used - and even labeled as granite, so you need to be careful when shopping. Two slab-wrap cups with inclusions attached. For those interested, I've just ordered a copy of Additions to Clay Bodies by Kathleen Standen. This can be had for < $20 from UK sellers with free shipping.
  5. Charles

    Varied Perlite inclusion results

    Rae - The studio manager says he can work with me to make a small test batch of ball clay. I can see how the plasticity of a ball clay would help here. I realized that using Porcelain for this was not a good idea, as I've had bad luck trying granite inclusions in it - the strength just isn't there. I tend to doubt that the firing method would really make much - if any, difference in this regard – based on my minimal knowledge. Yes - garden supplies, if there is any variation just how can one know about it? I don't know if it would just be in the source rock, or could be introduced in the expansion processing. Charles
  6. Charles

    Varied Perlite inclusion results

    Thanks to both of you. I was planning to try wedging tonight, and will do that with porcelain on two test pieces, one for each firing method. I had asked the studio manager if the ball clay would make any difference, and he doubted it. The school has frequent reduction firing, but I'll have to sign up for an electric kiln for oxidation, and will need to wait until I have other pieces to justify that. I'm also checking with ceramic sources in Australia to see if it might be the Perlite there.
  7. Charles

    Help needed to identify a mark

    Lee Ustinich has the right initials . . . .
  8. Here are photos of a Perlite facade on a vase I made last spring, and a piece I found yesterday called Organ from Louise Gregg of Australia. I found a site for her, but it hasn't been updated since 2012, and I can't find any other web references for her, so she might not be currently active in the arts. https://www.flickr.com/photos/29724621@N03/sets/72157701256082844 I don't understand how we could have achieved such different results - unless perhaps Aussie Perlite is of a different composition than American Perlite. However, I've seen variations in how Perlite performs. The first time I used it on a cup, it produced quite sharp edges, and the studio manager said it approached being dangerous to handle. There are some rough edges on the vase, but I can run my hand across the surface without any discomfort. I don't know if the dense concentration made the difference, or if something else was at play - both pieces were stoneware fired at ^10. I also don’t know why on my piece some pellets disappear, only leaving a hole where they once were, while others just become a globule in place - it might have to do with original size. Does anyone here have any thoughts on this?
  9. Charles

    Sand On Clay?

    Read the reviews on Amazon. Apparently lots of (poorly identified) photos, but very little discussion of technique.
  10. Kurinuki - starting with a 25Kg brick of clay ;-)
  11. Lee - thanks for the comments. > My guess is the texture in last one was made by scraping/digging (not tearing) when it was just a tidge shy of leather hard, but someone else may have other ideas. To my eyes it's too "delicate" for that. What I'm seeing is a series of very shallow ridges, with most of them less than 1 mm thick. Sort of like layers of miniature sedimentary rock that have been broken away? I also see an uneven surface texture, so don't know how that could be achieved by any kind of scraping motion. However - I know nothing of the internal structure of clay, so it could be something quite natural that I'm just ignorant of.
  12. Probably most so for the person/business who took the photo and had it on their site ;-)
  13. Hello - Charles in Boston here - a sporadic hobbyist and newbie to the forum. I've noticed a number of folks using faceting cuts with adjacent torn, roughly-textured sections between them. My supposition is that the cuts are made and then the remaining clay is left en situ while drying takes place, which is what causes the rough surface when this section is broken off. http://thebesttimeoftheday.blogspot.com/2011/03/jonathan-cross.html https://i.pinimg.com/originals/1a/1b/5a/1a1b5af98ede5823d73bc84c2e0bbca2.jpg https://www.etsy.com/listing/499699799/one-of-a-kind-wood-fired-yunomi?ref=shop_home_active_80 I realize the cup in the second image doesn't have the clearly defined chisel marks that Jonathan Cross pieces usually have, and no doubt these greatly help to sharply delineate start and stop points for the tearing. In this case I suspect the cuts were made, but then the cut clay was left to dangle while the still attached end-point dried up some before the tear. What I'm wondering is if you just let it air-dry, or use a hair-dryer or heat gun in the areas where you want the break? I'm curious if any particular motion of tear or break provides the best texture. Or - and most likely, is this just something that I will need to discover for myself? Also - the Pottery Park pieces often seem to have an unusual "layered" texture under the tear, but I have no idea of what is causing this - any guesses? Lastly - while admitting the addictive nature of Pinterest, I'm starting to feel loathing in that its proliferation makes it almost impossible to find the original source of a photo using Google image search. Charles

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