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  1. Charles

    Iron Oxide Slip

    My school only does one or two soda firings a semester, but I just saw this and really like the look - based on the foot it's a ~ dark tan -light brown clay. Wondering if this is likely achieved with a low percentage of RIO or something else? thanks
  2. Charles

    Clay Additives

    Last spring I was breaking up granite chicken grit on a metal table with a large-head hammer. I had the grit in a heavy weave fabric, but it was still a pain to gather the results, and repeated use wore it out. This fall I discovered miner's dolly pots, designed to be taken into the field. I started with the small, but moved up to large (13 #). I do recommend using this on a hard surface, such as a concrete floor or a cinder block. As a point of reference, they are designed for quartz (to look for gold), which is harder than granite. https://www.blackcatmining.com/mining-equipment/crushers.cfm If interested, you might want to order soon, as the owner Eathan (great customer service - ask for lower cost USPS vs. UPS shipping; the site only handles the latter, but he'll refund the difference) told me that the fellow who makes them is retiring - unknown if he will be able to find another source for them. The big benefit for me is that everything stays in the tube, so I can easily feed it into my smallest screen, or an intermediate container. I use a 20, 10, 6 and then 4 mesh. Anything that doesn't fit through that I just put back in the next cycle. Since I want it for visual effect, I consider anything smaller than 20 mesh as powder, with no need to differentiate it further, and will sometimes dust it onto a clay surface to add hints of another color. The main reason I'm replying now is something I just realized, based on a comment in an old Alfred Grinding Room Cookbook (I've been making some interesting - often groggy, clays based on recipes from 2004-2007) that relates to the initial post. I had been rolling thin slabs, sending them through bisque, and then breaking them up and screening. Before making the grog I had just been breaking up the dried slabs and using that directly. I switched when I wanted to include foreign clays in new bodies I was making, vs. rolling them into slabs of commercial clay. Anyway, instead of having to break up fired clay, it makes much more sense to do the breaking and screening with the dried clay, and then sending that through bisque. I saw this in reference to 10-20 grog, so if you're looking for something finer it's possible that the clay bits might tend to reattach in bisque? Also, this fellow was coloring his clay body with 10% Mason stain before drying it out, if anyone is looking for colored grog. As mentioned, I had formerly been using broken up clay bits, and I'm still not sure that wouldn't work just as well as grog - for visual effect. Here is an early "slab-wrap" cup from mid-winter with mixed clay bits rolled onto the slab before forming the cup. My studio manager suggested that the clay bits would have the potential of absorbing some water from the moist clay. However, the clay body has often peeled back some from the larger chunks, suggesting that any water the main body lost was not transferred to the dried clay. Again, this may be different for small mesh sizes. YMMV BTW - I noticed that I spoke of raw coal slag in the previous post. Here's the plate out of high-fire. I love the rusty Death Valley clay, but wish I had varied the size of the coal slag more (or only used fewer and smaller pieces), as there are too many largish metallic-looking bumps for my taste. I'll likely not use them for plates again - although, I've been using this for Cape Cod Dark Russet chips.
  3. I want to lay a pattern out on a soft slab - preferably using some sort of soft marker that will not withstand firing. It's actually some points that are boundaries and I had been pressing lightly with a rounded tool, but I'm finding it's an effort to cover the impressions. I have no idea if the ink in a "permanent" marker is permanent at 2345 F. thanks
  4. 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.
  5. 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?
  6. 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
  7. 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.
  8. 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
  9. 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.
  10. Charles

    Help needed to identify a mark

    Lee Ustinich has the right initials . . . .
  11. 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?
  12. Charles

    Sand On Clay?

    Read the reviews on Amazon. Apparently lots of (poorly identified) photos, but very little discussion of technique.
  13. Kurinuki - starting with a 25Kg brick of clay ;-)
  14. 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.
  15. Probably most so for the person/business who took the photo and had it on their site ;-)

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