Tubes From Porcelain

[Leola]

Dear Ceramics Artists, 

 

A while ago i have posted a question regarding making of tubes from clay (stoneware). Actually now i'm trying to do it with porcelain, but find it cracking. 

Would like to ask for suggestions on this. 

I'm working with a slab, and a rubber tube around which i make the slab. 

But next morning it was cracked. And the release of the tubes seems to be quite harder to release from the clay. 

Can anyone advice me on this part? I like to make it as thin as possible. 

Looking forward, 

 

Thank you 

[bciskepottery]

Are the cracks along the seam or elsewhere? The clay may be cracking because it is drying and compressing (shrinking) against the rubber tube; you may need to remove the rubber tube earlier or slow down the rate of drying.

 

Try wrapping the rubber tube with newspaper; it will make it easier to remove the tube. Or, I put an old knee-high nylon stocking on my plastic and cardboard tubes that I use as forms; the clay will not stick to the nylon.

 

If you want thin, think about using a porcelain slip and dipping a clay/plaster/other tube into the slip, allowing it to set, then repeating until you get the thickness/thinness you want; then remove the tube from the form before too much shrinkage. That would eliminate any seams at all and potential warping at the seam when firing.

[Diane Puckett]

I saw a video where Lorna Meaden was making a watering can with thin slabs. She rolled a very thin sheet of plastic, perhaps Saran Wrap, onto one side of the slab and left it on the slab while she made the form. You would just need to uncover the edges to join them. The plastic would stabilize the form until you had it manipulated onto your form, and then you could remove the plastic. That might protect the porcelain from some of the stress which can lead to cracks. I have found that the thinnest plastic drop cloths are good for this. I buy them at Lowe's in economy boxes.

 

If it would be the right size, you could try making your tubes around an inflated balloon, still covering the balloon with newsprint. When the tube had set up a bit, you could pop the balloon. I have no idea if this would work, but if it did, it would put less stress on the clay. You really have to get that slab off the form pretty quickly, especially with porcelain, as it dries fast.

[Chris Campbell]

Pictures would really help here so we could see what you are doing.

It would be helpful to know how much give there is in the tube form too.

Like bciskepottery, I wrap my supporting tubes in paper then remove them as soon as possible so the clay won't shrink and prevent the removal. In a dry studio this can happen in minutes so you need to watch your work closely. Almost any clay would be cracked by the next morning unless your support has a lot of give to it.

[Marcia Selsor]

I just made some yesterday for foil saggar test tiles. I wrapped newspaper around a PVC pipe, joined the seam, cut them into four sections slid them offthetube and newspaper and stood the up.

 

Is this rubber tube shaped or bent?i think you should not leave it over night to set up.

What is the scale? Four inch diameter, 6", 8"?

 

For 8" diameter , unlike Lorna Meadon, but similar idea, I use tar paper on the outside of the slab and tube with sleeve of newspaper on the inside of the slab. I remove the tube with the paper sleeve minutes after standing up a 28" tall tube or larger as I pictured in the first post when you asked this before.

 

Marcia

[porcelainbyAntoinette]

Lala, consider covering the tube first with paper, then with with a sheet of foam and then plastic. The foam will give as the clay shrink and allow you to slip the whole wrapping off the tub. 

A few more things to consider: When you create the slab, make sure that you spread the clay in all directions, so that it does not shrink more in one direction than the other.

Also; Make sure that you wedge your clay a few hours before you use it and again right before you throw or roll the slab. The moisture content must be very evenly spread, particularly for porcelain.

A last suggestion: make sure you do not stretch the clay in the handling process. Roll up and unroll over your tub or roll on plastic and handle while it is still clinging to the plastic. Breaks in the clay can happen and you will not even know that before it is fired in some instances.

Hope this add to what everyone else already suggested.

[Mark C.]

Depending on diameters I would shoot tubes with my extruder(up to 3inch)-I have done a fair amout of porcilain ones in the salt kiln years ago with no cracking.

As far as Handbuilding take the advice above from thiose who handbuild more than I as do very little anymore.

Mark

[Leola]

Dear all, 

Thank you for the very helpfull reply. 

What i do is my tubes are around 3 centimes in diameter. I bend them. Was so amazed with porceline that i could bend them more sharply then other clays. But ye, couldn't remove it from the rubber tube. Maybe also i was to enthousiastic dreaming of translucent thin and need to take it easier and practice practice practice. Actually also i like to ask if it is possible to use vaseline on the tubes or will this affect the porcelain? 

Will try to make some images once i make another attempt. 

Also im working in India and it is getting pretty hot here now, daily temperature is 32 degrees around. Maybe that affects it.

Thank you also for the helpfull explanation for the slab. I realize that with this type of clay i need to approach it very consciously, like as if says, if you wanna work with me im beautiful, but handle me with dedication. It's great!

[Leola]

The cracks, was one crack over the lenght of the tube

[Diane Puckett]

I would not use Vaseline. I don't think it would help, and it is probably not a good thing to put in the kiln, as it is petroleum based. I have seen people use talcum powder (baby powder) to keep clay from sticking to things, but I doubt it would work well enough to replace paper. The powder just burns out in the firing.