Wednesday, December 16, 2009

good advice..

being an artist on facebook can be both good and bad... good for being able to check out others's work, staying connected with friends, comrades, customers, and getting advice on all kinds of issues pertaining to art..there are thousands of years of experience on the fb. pretty cool. here are some great tips i got, wasn't expecting this level of advice, potters rock!...maybe you can use it so i will pass it along:) here is a video of the large and xtra large platters i am going to try and successfully fire. whew, i need a larger kiln...Justin Rothshankslow down everything. bisk, glaze, and cooling.
Yesterday at 10:24am · Delete

Shannon epk underneath the platter will help (works as ball bearings)
Yesterday at 12:27pm · Delete

Lee Also heard recently, that if you fire the platters braced in a verticle position, this helps. (Rather than stacking the flat.) Have no first hand experience on this, as haven't yet done platters.
Yesterday at 12:42pm · Delete

Richard P Compress the plate very well while you're working it on the wheel. They're right,,,slow down the production processes. Slow dry,slow bisque with controled down ramp. Use something that acts as a agent that lets the plater move during firing.Down ramp the glaze fire also. Large platers are a pain.
Yesterday at 3:18pm · Delete

Euan I haven't bisqued for 15 years, so there is a lot of shrinkage in the firing.The largest I have worked with are 95cm fired, but I haven't done anything that big since moving from the pokey little house with the big studio to the big house with the pokey little studio. The percentage doesn't change regardless of size, but the actual shrinkage distance does. So for a 22" plate, with 10% shrinkage, that means it shrinks 2.2". That's a long distance to drag across a kiln shelf, so the advice about EPK (thanks Shannon and Richard) or some other powder that acts like flour when you roll out dough is really good. I personally use Alumina, as I wood/soda fire and Kaolin can flux out, sticking the pot to the kiln shelf.

If the cracks you get are firing cracks rather than stress/shrinkage cracks, then you need to go slow around 573 Celsius, when the alpha beta quartz conversion happens. If your heat source is directional (as mine is with the wood kiln) the front of the pot can heat up faster than the back of the pot. So with a large platter one side could reach expansion point before the other, expanding the silica by 2%, and the stress between front and back (or outside and inside on large encolsed forms) can cause firing cracks.

There is always the possibility that the cracks occured during drying. Again, the shrinkage stress. You need to get them off the throwing bats as soon as possible. I dry large work on two sheets of newspaper with corn starch dusted between. It allows even drying which prevents warping as well as the free movement to avoid shrinkage stress. ...
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Yesterday at 6:15pm · Delete

Patricia Euan certainly is right on target. The only difference for me is that I do bisque. Upside down on 50 mesh grog. I also slow it way down doing the alpha beta quartz conversion on the way up and on the way down. I also put aluminia hydrate on the shelf for the glaze run. Good luck!
Yesterday at 7:11pm · Delete

Richard Wow,,,what fantastic skills are out there. It's all solid advice Jeff . I use grog. It's cheap and has done the job for me for 35 years.It doesn't srew up an element is it get on it.
Dale Neece and I use plaster board cut to dimention to rest and dry our mega plates on. It obsorbs the moisture and supports the ware,covered with plastic to control the drying. Compression is a really big issue. Large platers are still a pain..........
Yesterday at 9:35pm · Delete

Jeff Martinwow..i am printing this comment run out, very solid advice. thank you so much, i feel like i have some tools to use going in. i have done platters around 20" and always lost 50%, so it was quite discouraging. i use drywall board, it seems to pull moisture fairly evenly, but the cornstarch sounds helpful. euan , are you putting a piece of paper on ...
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Yesterday at 10:03pm · Delete

Agp ArtstudioYou guys are the best! I made a note of everything and will definitely take things a lot slower in the future with my large platters. Thanks,
10 hours ago · Delete

Euan Call it a double layer of news paper, underneath only, with cornstarch between the layers and between the paper and the pot. It serves the dual purpose of allowing the plate to shrink without friction and also even drying. The exposed top surface of the plate or slab will dry normally, and the newspaper will "Crinkle", (in the potato crisp sense) which allows air to circulate underneath the plate as well so that you get even drying, therefore less warpage.
5 hours ago · Delete

Jeff Martin brilliant! newspaper is the duct tape of the paper industry...
about an hour ago · Delete

2 comments:

Linda Starr said...

Thanks so much for printing all this here as I would have missed it on fb, lots of good info on drying and bisque firing. For my cone 10 porcelain and stoneware platters and large plaques I used porcelain sand under them while firing and this helped to reduce warping and cracking.

Dirt-Kicker Pottery said...

Great information. Thanks for sharing. Your platters are totally cool! I love the rims.