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JeffK

Joining a bowl and pedestal

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I'm a relative newbie - been at the wheel for about a year. Have spent most of my time at the wheel practicing forms.

Last week I tried something different - threw a bowl and then a separate pedestal which is essentially a small bowl itself. I let them get to leather hard, trimmed, then scored the bottoms and joined the 2 pieces together with slip.  Cleaned the connected area a bit today by trimming off the rough leftover slip. But I noticed that I didn't completely fill the gap in a spot where the two edges meet. The piece is now bone dry. Can I add a bit more slip the the gap and smooth it out before bisque firing? Will it stay in place or just crumble off since it's a bone dry piece?

All guidance welcome.

- Jeff

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Good question!

If the gap is small enough to bridge with glaze, an opaque glaze would, err, may hide it.

You might try misting the area with water (spray bottles are an essential!), just a little bit, for too much with melt your work, wait a while, mist a bit more ...until the area is damp enough to accept some slip. If you really like the piece, try it out on some scrap stuff first.

Paper clay, sounds good.

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2 minutes ago, Hulk said:

Good question!

If the gap is small enough to bridge with glaze, an opaque glaze would, err, may hide it.

You might try misting the area with water (spray bottles are an essential!), just a little bit, for too much with melt your work, wait a while, mist a bit more ...until the area is damp enough to accept some slip. If you really like the piece, try it out on some scrap stuff first.

Paper clay, sounds good.

Top both Liam and Hulk - thanks for the suggestion of paper clay. Not sure I need that much of an aggressive repair.

The gap itself is only about 1/16" inch (.159cm) and is right where the two pieces join.  I though also that the glaze may fill/cover it.
Then I began to second-guess it. This is how obsessive I can get. :)

I may dampen the area as suggested and brush a bit more slip in there.

Thank you both for the suggestions!

- Jeff

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6 minutes ago, JeffK said:

Top both Liam and Hulk - thanks for the suggestion of paper clay. Not sure I need that much of an aggressive repair.

The gap itself is only about 1/16" inch (.159cm) and is right where the two pieces join.  I though also that the glaze may fill/cover it.
Then I began to second-guess it. This is how obsessive I can get. :)

I may dampen the area as suggested and brush a bit more slip in there.

Thank you both for the suggestions!

- Jeff

I like both suggestions but any water will cause the repair  to shrink as it drys so at this stage if you do fill it compressing the joint as it dries with a small ball bearing ended tool this  often gets the repair dense enough to offset the inevitable shrinkage. This works great on sharp edge joinery and provides a little more insurance to the repair.  In the event there is a very small gap after bisque, you can still fill with some bisque fix,, glaze and have your perfect pot.

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1.5mm is a bit big for a glaze fill.  I just suggest paper clay (slip) because it doesn't shrink as much as normal slip.  I wouldn't just leave it because if it has pulled away visibly from the joint, the entire joint is compromised.

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Hi all -

Many thanks for your suggestions. I am concerned about the integrity of the joint and not just the cosmetics and may opt for the paper clay or spooze (had to look that one up).

Just curious - couldn't I mix up some defloculated slip and epsom salts and then push that into the crack?

- Jeff

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jeff, yes, you can DO anything.  sometimes things you try work and other times it does not.  that is how we learn.

you are at that stage in becoming a good potter where every piece is precious to you.  it is very hard to realize that each unexpected thing is a way to improve your skills by working through the new problem.    it is difficult to realize that the piece in your hand might not make it to the finish line.  but it is. after all, only clay and if you could do it once you can do it again.   by the time you have made 6 of them, the first will only be an experiment and the last something to treasure.

one thing you might want to do is learn more about your clay.   if you take a piece of dried scrap bigger than one inch square and quickly dip it into clean water to wet it, then scrape it with a sharp tool, you will see how little effect the water has on the bone dry clay.    do it repeatedly so you can gauge the amount of water it takes for the clay to fail.   

once you know this, you will be able to judge what will work and what will not.

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5 hours ago, JeffK said:

Hi all -

Many thanks for your suggestions. I am concerned about the integrity of the joint and not just the cosmetics and may opt for the paper clay or spooze (had to look that one up).

Just curious - couldn't I mix up some defloculated slip and epsom salts and then push that into the crack?

- Jeff

To answer your question I like that fix and believe it is fairly successful. Mixing an overly thick clay rich slip using Darvan  or equivalent and then taking a portion of that slip flocculating with Epsom salt solution to a creamy  sticky thick texture works reasonably well as a clay glue and filler.  We keep some mixed all the time and flocculate portions for repairs as needed.  Again the item of primary importance is limiting shrinkage and final density of the repair so whatever you fill the crack with, adequately compressing it into the void is almost always helpful.  in many construction practices we compress things (Road beds, Gravel, Clay bases) to remove water and tighten the structure, clay is not a bunch different in this respect in my experience.

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Whatever you try, make sure everything is well dry before you bisque.

Can make an excellent repair only to blow it by assuming all is dry a little later.

Moving on, 

Throw your bowl, let it firm, tidy up the bottom of pot, place upside down on wheelhead, attach a thick coil on  on bottom if bowl then throw your pedestal.

Dry slowly.

Just saying.

Edited by Babs

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All of you have been wonderfully helpful and I appreciate you all taking the time to respond. This can be such an overwhelming endeavor - the more you know the more you need to know, But as oldlady said above, and I paraphrase, there is no failure - only ways to continue to learn.

As a postscript, went back to the studio yesterday afternoon to continue to work on the piece. Now I trimmed and put these two pieces together on Saturday, came back Monday to check, and that's when I saw the gap. Panicked a bit and wrote in here. So went back yesterday (Tuesday) with a plan but apparently as the joined pieces dried out,  shrank, and possibly warped a bit, the small gap disappeared. Now the question - and hope - is that when I bisque it, the joint will survive.

Always a school day in the studio. :)

- Jeff

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Just out of curiosity and for future reference Jeff, when you attached the pedestal that you described as a bowl, did it have a bottom on it? If so, you may have a bigger problem as the two layers of clay may have an air pocket between that could cause the join to separate in the firing. If you removed the bottom of the pedestal bowl before joining you should be alright.

 

 

best,

Pres

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I agree with Oldlady in that you might learn more from allowing this piece to break in order to see how far you can push your clay. 

A trick I was taught for attaching handles that applies to attaching other solid parts is to press and wiggle the pieces together until you can feel them grab AND you should see slip oozing out from all areas of the attachment point. Use a clean, soft but firm pointed paintbrush (I like an artificial sable) to wipe away the excess slip. The brush will make the join look neat and tidy without distorting anything. As the piece dries, some of the slip will shrink back into  the join, and the resulting line will fill with glaze. 

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6 hours ago, Pres said:

Just out of curiosity and for future reference Jeff, when you attached the pedestal that you described as a bowl, did it have a bottom on it? If so, you may have a bigger problem as the two layers of clay may have an air pocket between that could cause the join to separate in the firing. If you removed the bottom of the pedestal bowl before joining you should be alright.

best,

Pres

Pres - that is my most honest mistake. I had just created this using a visual so there's a bottom on the bowl and on the pedestal. Seemed logical to me. When I joined them, I heavily scored and slipped.

I hadn't asked my instructor about it so when he saw what I had made - this was during open studio time so he wasn't there - he asked the same question. He offered that next time, just go to the bottom of the bat when I create the pedestal and then join the two using a coil. Another member suggested that I just leave a ring on the pedestal and use that to mount to the bottom of the bowl.

Will have to wait until it comes out of the kiln to see the final result.

- Jeff

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5 hours ago, Callie Beller Diesel said:

I agree with Oldlady in that you might learn more from allowing this piece to break in order to see how far you can push your clay. 

A trick I was taught for attaching handles that applies to attaching other solid parts is to press and wiggle the pieces together until you can feel them grab AND you should see slip oozing out from all areas of the attachment point. Use a clean, soft but firm pointed paintbrush (I like an artificial sable) to wipe away the excess slip. The brush will make the join look neat and tidy without distorting anything. As the piece dries, some of the slip will shrink back into  the join, and the resulting line will fill with glaze. 

Hi Callie -

That was my approach. I used a needle tool to heavily score both pieces, used some thick slip, and pressed the pieces together. I actually added some additional slip around the joint thinking I would just trim it off. The small gap may have been from me not pressing down hard enough or maybe I wasn't attentive enough when putting the final slip on.

Pres raised another issued - both pieces had solid bottoms and that's how I joined them. Now to see if they survive the kiln.

- Jeff

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Some people like to throw the two sections with bottoms, as this makes it easier to lift off the wheel without warping. Myself, if throwing the pedestal section throw it on a bat without a bottom. Another option here is to throw the pedestal with a thicker (slightly) rim, as the piece will be resting on it, makes for a nice base line. Other options are to cut the pedestal with four parabola/hyperbola shapes. I use a thin walled brass pipe, I keep many diameters as hole cutters for all sorts of pieces, often cutting the foot rings for nicer dishwasher drainage.

 

best,

Pres

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