How do you keep hand-built cups round?

[lincron]

I have been handbuilding pottery for about a year. I have tried many times to make cups from a slab. I try to form the cups around another "cup" shape, but of course it has to be removed before it's dry or it will crack as it shrinks. I have watched and tried to reshape the cups into round as they dry, but it seems no matter how carefully I do this, in the end they end up distorted. I assume this is due to uneven shrinking, but I roll my slabs out on a slab roller so the walls are even. The only place they are not even is where the slab is joined. I have also tried to let the cup dry slowly by wrapping it in plastic. I would appreciate any advice.

[Ducky]

I have been handbuilding pottery for about a year. I have tried many times to make cups from a slab. I try to form the cups around another "cup" shape, but of course it has to be removed before it's dry or it will crack as it shrinks. I have watched and tried to reshape the cups into round as they dry, but it seems no matter how carefully I do this, in the end they end up distorted. I assume this is due to uneven shrinking, but I roll my slabs out on a slab roller so the walls are even. The only place they are not even is where the slab is joined. I have also tried to let the cup dry slowly by wrapping it in plastic. I would appreciate any advice.

 

 

Check out this and parts 2, 3, and 4 on youtube:

When I build round things like cups I leave it on the form until it stiffens up enough to stand up on its own. Hope this helps!

[pricklypotter]

I have been handbuilding pottery for about a year. I have tried many times to make cups from a slab. I try to form the cups around another "cup" shape, but of course it has to be removed before it's dry or it will crack as it shrinks. I have watched and tried to reshape the cups into round as they dry, but it seems no matter how carefully I do this, in the end they end up distorted. I assume this is due to uneven shrinking, but I roll my slabs out on a slab roller so the walls are even. The only place they are not even is where the slab is joined. I have also tried to let the cup dry slowly by wrapping it in plastic. I would appreciate any advice.

 

 

Interesting reply video, thanks! Very methodical.

 

My two cents: if you're shooting for even, definitely do the upright tube and wait until at least soft leather hard to take it out. However to me, an almost-even shape and almost-invisible seams are less appealing than unapologetic seams and deliberate 'wonk' in a piece so I now make slab cups and mugs completely soft so that they develop those nice dips and bulges that glazes love so much. I wish I had some on me to post but the old ones are gone and and the new ones are waiting patiently to be fired.

 

PS I also disagree with her handle... If my knuckles touch the mug when the hot tea is inside, I find that uncomfortable. But I also don't like 3-4 finger handles so I'm strange this way.

[bciskepottery]

If you overlap the seams, the clay has a tendency to distort because the seam is thicker and does not dry evenly with the rest of the cup. You can help give your clay new memory by placing the cup slab on a piece of foam and using a rolling pin or cardboard tube to create a round -- not flat -- memory. You can try beveling the ends of your slab to reduce thickness, then join with slip. You can also use a rasp or wire brush to remove some of the clay at the ends. To keep a round shape once the cup is formed, put a styrofoam cup inside the clay cup (let the fit be relaxed; not jammed in). I cut the bottom half or so of the styrofoam cup off, leaving only the top part . . . that way the styrofoam cup will give as the clay firms up and begins to shrink. Dry slowly.

[DirtRoads]

I asked this and was told "learn to throw on a wheel".

[koreyej]

I am a fan of the deliberate "wonk" as well. I had a very sage instructor who asked me once, "If you really want it perfectly round, why not just buy it at Target? It's cheaper in the long run". This question began the slow demise of my perfectly round work. I think it all depends on what kind of potter you want to be: one who makes the clay bend to his will and say what he wants it to, or one who discovers what the clay has to say. That said, if you want that roundness, bevel the edges and join on the bevel. Either use magic water for the joint or slip/score and dry slowly. Good luck!

[Diana Ferreira]

I use spann rings. It is plaster shapes and I rest my round shapes on it upside down while it dries. If you 'sock' your shape with some stocking, it will be easy to remove it from the shape that you created your mug on.

 

*** I know that I have posted an image of my spann rings somewhere on the forum, but cannot find it now :-(

[perkolator]

when I make cups or cylinders from slabs, i like to use a cardboard tube or ABS pipe as my form. wrap 1-2x with newspaper or paper towel. as for the seam -- miter your seam at 45* for more surface area and the walls usually come out even vs overlapping. I usually add the bottom while it's still on the form, then remove it when clay is chocolate-hard so a handle can still be added. as for the warping you're getting - pay attention to how you manhandle the clay when you remove it from the mold -- remember clay has incredible memory, so if you bend or warp part of it at any time it will remember this and usually warps that direction. hope this helps.

[~janie]

When I make handbuilt cups, I put a hole in the bottom of a clean can - from green beans, tomato juice, or even a beer can- and wrap the can in newspaper. Use masking tape to hold it in place, then wrap with your slab of clay, with the can upside down. I use paperclay slip to join, as you can get good adhesion with a very light touch. I leave it for a little time, to give the clay a chance to set up, then pull the can out of the clay, using the hole in the bottom of the can as an aid, and leaving the newspaper in place. If I am going to make a folded bottom, I do so before the can comes out, otherwise put the bottom on when the cup is leatherhard. I also like seeing signs of my work. Perfect isn't all it is cracked up to be, IMHO.

[Mossyrock]

I have various sizes of balls (those filled with air) in my studio. They're great for keeping handbuilt pieces round while drying....they're lightweight and I lightly press the size needed into the vessel opening....just enough so that the rim is rounded. Occasionally I'll take the ball out and 'reseat' it as the clay gets drier........ I've never had a piece break or split. I guess the ball 'gives' enough to allow for the drying process while keeping the opening round at the same time. I also like to see 'signs' that a piece is handmade and not perfect, but I don't like a 'warped' look that happens during the drying process.

[macdoodle]

i have seen a you tube demo, which i can't find right now , where a young man has the curved shaped slabs cut out and then after attaching to the round base and making a good seal up the seam, he uses a wooden egg ( via the hobby store) inserted and given a swirl to round the lip back up. These were very thin put together leather hard (except possibly the base) and seemed to stay round. I also notice that with slab forms, if you have any part out of round sometimes in bisque, but usually in cone 10, that out of round area will take the brunt of any slump or shrinkage distortion. Lids that fit well after fire on a non standard hand /slab formed shape are still often illusive for me. Some of this may be because slab and hand construct does not align the particles as well as throwing. The latest instructional done by Joyce Michaud on this site shows a technique while not slab is a hand construct technique that seems to create the same alignment of particles you and I may be after.

[macdoodle]

I asked this and was told "learn to throw on a wheel".

 

 

LOL- or the instructor needs to learn some more hand build techniques? but I wouldn't tell them that.. Could be that you need to find someone who specializes more in the type of work you want to learn.

 

“Everybody is a genius. But if you judge a fish by its ability to climb a tree, it will live its whole life believing that it is stupid.â€

― Albert Einstein

[westoreshop]

THE MORE I LEARN, THE LESS I KNOW

[clayshapes]

Like some others here, I always prefer the wonk to the perfect -- but I found this video very helpful. I make tumblers, without handles -- but you could easily add a handle using this method:

[lincron]

I asked this and was told "learn to throw on a wheel".

 

 

Haha, yes I've heard that too, and I do throw on a wheel, or at least I did until I got tendonitis. So that is no longer an option for me.

[lincron]

I am a fan of the deliberate "wonk" as well. I had a very sage instructor who asked me once, "If you really want it perfectly round, why not just buy it at Target? It's cheaper in the long run". This question began the slow demise of my perfectly round work. I think it all depends on what kind of potter you want to be: one who makes the clay bend to his will and say what he wants it to, or one who discovers what the clay has to say. That said, if you want that roundness, bevel the edges and join on the bevel. Either use magic water for the joint or slip/score and dry slowly. Good luck!

 

 

Thanks for the input. Maybe it's time to come to terms with my bent towards "perfectly round."

[lincron]

If you overlap the seams, the clay has a tendency to distort because the seam is thicker and does not dry evenly with the rest of the cup. You can help give your clay new memory by placing the cup slab on a piece of foam and using a rolling pin or cardboard tube to create a round -- not flat -- memory. You can try beveling the ends of your slab to reduce thickness, then join with slip. You can also use a rasp or wire brush to remove some of the clay at the ends. To keep a round shape once the cup is formed, put a styrofoam cup inside the clay cup (let the fit be relaxed; not jammed in). I cut the bottom half or so of the styrofoam cup off, leaving only the top part . . . that way the styrofoam cup will give as the clay firms up and begins to shrink. Dry slowly.

 

 

Good tip, thanks for sharing this.

[lincron]

I have various sizes of balls (those filled with air) in my studio. They're great for keeping handbuilt pieces round while drying....they're lightweight and I lightly press the size needed into the vessel opening....just enough so that the rim is rounded. Occasionally I'll take the ball out and 'reseat' it as the clay gets drier........ I've never had a piece break or split. I guess the ball 'gives' enough to allow for the drying process while keeping the opening round at the same time. I also like to see 'signs' that a piece is handmade and not perfect, but I don't like a 'warped' look that happens during the drying process.

 

 

I like this idea! Could you give me a better idea of what these air filled balls are? Or tell me where I can purchase them? All I can think of is a beach ball---way too large!

Thanks!

[lincron]

i have seen a you tube demo, which i can't find right now , where a young man has the curved shaped slabs cut out and then after attaching to the round base and making a good seal up the seam, he uses a wooden egg ( via the hobby store) inserted and given a swirl to round the lip back up. These were very thin put together leather hard (except possibly the base) and seemed to stay round. I also notice that with slab forms, if you have any part out of round sometimes in bisque, but usually in cone 10, that out of round area will take the brunt of any slump or shrinkage distortion. Lids that fit well after fire on a non standard hand /slab formed shape are still often illusive for me. Some of this may be because slab and hand construct does not align the particles as well as throwing. The latest instructional done by Joyce Michaud on this site shows a technique while not slab is a hand construct technique that seems to create the same alignment of particles you and I may be after.

 

Thanks for your input. I'll see if I can find that video. I've seen one (video) on this website where a cone-shaped spool is used, but I had no idea where to get one. I think I've see the eggs though. Maybe I'll also start wedging my clay before I roll out the slabs to align the clay particles, that is a good thought. I never have problems with "S" cracks, so I did not consider wedging important. Not one of my favorite things to do, but I guess it's time to work on that skill.

[lincron]

Like some others here, I always prefer the wonk to the perfect -- but I found this video very helpful. I make tumblers, without handles -- but you could easily add a handle using this method:

 

 

Great video! Thanks.