Plates.....Pointers appreciated

[Bill T.]

I have a commission to throw several plates and soup mugs. Sometimes I'm lucky with a 9" plate and it remains flat after glaze firing, but other times???? Using B-mix to Cone 6. Good compression of the bottom, not to large of a lip, thickness of lip about 5/16. Bottoms about 5/15 after drying, slowly..slowly flipping on bats. This time did not cut a foot, just trimmed carefully to edge for a nice slope. Will do a slow bisque to 04, wipe with sponge , brush 3 glaze coats, medium speed to Cone 6.

 

Questions: Is my bottom too thin? My lip too thick?

 

Any more thoughts? I did throw a couple extra just in case.

[TypicalGirl]

What's the defect?

[Pres]

I have a commission to throw several plates and soup mugs. Sometimes I'm lucky with a 9" plate and it remains flat after glaze firing, but other times???? Using B-mix to Cone 6. Good compression of the bottom, not to large of a lip, thickness of lip about 5/16. Bottoms about 5/15 after drying, slowly..slowly flipping on bats. This time did not cut a foot, just trimmed carefully to edge for a nice slope. Will do a slow bisque to 04, wipe with sponge , brush 3 glaze coats, medium speed to Cone 6.

 

Questions: Is my bottom too thin? My lip too thick?

 

Any more thoughts? I did throw a couple extra just in case.

 

 

I do patens(communion plates) quite a bit. Some of the tips I would give are 1)wetter than usual clay. 2) compression, compression, compression. I use large wooden, plastic or ceramic curved ribs laid at 30 to the plate working back and forth until about 5/8 thick. 3) compresss the edge clay before pulling into the rim, and compress the rim.

 

When trimming the patens I usually include a double foot ring as this helps with warpage on a 10 bottom circumference. I dry slowly, and then do an overnight water smoking and a slow bisque. When packing the kiln, I box the patens in pairs. Full shelf support. Glaze fire, again full shelf support with a light skim of grog on the shelf.

 

It may be overkill, but it works for me. At the same time I do throw extra, but then I usually end up with extra in the same amount.

[Bill T.]

Thanks for the pointers. I got an Ah-ha moment this afternoon remembering a video by Bill Van Gilder. His technique is a lot like yours. Threw 2 this afternoon and they feel stronger. Still going to throw an extra or 2.

[Benhim]

When I make plates I use wet clay. I compress the plate well by throwing back toward center once the plate is opened flat. I then wet the clay with slip and compress from the outside and across the center of the plate. I repeat this at least twice to refine my shape and compress the plate. Once that's done I cut it off the bat and set it aside. I then allow to dry enough to flip and then cut some of the supporting clay off the bottom with an open cheese wire. This aids in drying the plate more uniformly and the wire does not put very much pressure that might otherwise throw off the form. Later I come back and finish trimming once the plate is leather hard. I don't make plates out of smooth clay that has no grog. I've found much disappointment in S cracks in finicky clay bodies like B-mix. If I want the look of a clay like B-mix I throw the B-mix clay body with grog, I'll trim fairly thin and then apply B-mix body slip at leather hard stage. Using a deflocculated slip made from the body provides the look of the smooth clay and being deflocculated the slip firms more quickly helping to prevent the pot from becoming too wet and collapsing.

[Pres]

When I make plates I use wet clay. I compress the plate well by throwing back toward center once the plate is opened flat. I then wet the clay with slip and compress from the outside and across the center of the plate. I repeat this at least twice to refine my shape and compress the plate. Once that's done I cut it off the bat and set it aside. I then allow to dry enough to flip and then cut some of the supporting clay off the bottom with an open cheese wire. This aids in drying the plate more uniformly and the wire does not put very much pressure that might otherwise throw off the form. Later I come back and finish trimming once the plate is leather hard. I don't make plates out of smooth clay that has no grog. I've found much disappointment in S cracks in finicky clay bodies like B-mix. If I want the look of a clay like B-mix I throw the B-mix clay body with grog, I'll trim fairly thin and then apply B-mix body slip at leather hard stage. Using a deflocculated slip made from the body provides the look of the smooth clay and being deflocculated the slip firms more quickly helping to prevent the pot from becoming too wet and collapsing.

 

 

Yes, I figured throwing on a bat and cutting off immediately was a given, but then there are newbies here that wouldn't know that. Thanks for the reminder. I do use a cone 6 slip at times to press rubber stamp decoration into and to do other decoration. Especially works well when two undercolors of clay will make things more interesting.

[Idaho Potter]

I throw all my plates on a plaster bat and never wire off, just let it release itself. I keep the plate lightly covered with plastic bag or wrap until it releases then set it aside until suitable for trimming. Always a double foot on anything over six inches in diameter. As said above--compress, compress, compress.

[Benhim]

My favorite instructor in College Wally Schwab used plaster bats. I haven't gotten around to making them as of yet, but he was very successful at extremely large platters with that system. He did however use a red stoneware laced with a special iron product that was chunky as well as about 10% grog.

[Darla]

I use hydrobats..... never have to wire off, and don't have to worry about "my" plaster bats being "right". (I tried years ago, to make my own plaster bats, and there is a trick to getting those right, that I never could get.)

[Benhim]

I think the major problem people have with making anything out of plaster is they choose to purchase the wrong plaster. No. 1 pottery plaster is one of the more common ones I see people use and it's just so soft for the majority of what I do. I make molds for myself out of a plaster cement that's pretty tough stuff. It doesn't draw the water quite as quickly, but the rate at which No. 1 pottery plaster draws water can actually be detrimental to the work. Hydrostone was the one I used last time I made molds. It's not quite as forgiving as No.1 pottery plaster in liquid content, but that's not really an issue for me. Some of the plasters especially the higher grade ones made for press molding are difficult to work with. I found Hydrostone to be durable and it mixed with no problems.

[Idaho Potter]

On another forum dealing with plaster bats, I posted that I used industrial plaster. Harder than pottery plaster but more absorbent than Hydrostone. As to forming the bats, I use springform cake pan rings (no the bottoms); placed on Formica (make sure your work table is level); use Murphy's Soap as a release on metal rings and Formica; seal edges with clay. Mix plaster and gently pour into form. As it sets up, release latch on springform ring and then use a Stanley SurForm to round edges so bats don't chip. Let age at least a week before using. NOTE: make sure to thoroughly clean up plaster debris as it is not friendly to studio work.