Warping on glaze fire

[ronfire]

I have an issue with the butter dish lids that I make, they will at time warp out of round on a cone 6 glaze fire. The lids can not be fired on the bottoms because I gaze the bottoms inside and out. I try to place the bell lids in the center of the shelf with other items around to help heat from all sides but this does not always work. I was thinking of making some round disks to set the tops on so that hopefully they will heat and shrink the same instead of on a shelf.  Can I reuse these disks for several cone 6 firing or would they be problems to fire several times at cone 6. Was also thinking of covering them with a kiln wash encase the glaze creeps at all. Would it help if I had groves in the disk to help hold the tops in shape or would a flat disk be best. 

Thought I would  ask as I am sure someone has had the same issues and found some answers.

Here is a pic of the butter dishes before I bisque them assembled.

 

 

[Min]

Very thin and flat discs made out of the same clay as the body is what I use. I dry them between batts or drywall ware boards to keep them flat and cut the center out of them to use less clay. Don't have to bisque them as clay doesn't shrink much between bone dry and bisqued, could put some wash on them if you use runny glazes, no grooves. I seem to remember you use M340, don't need wash on them to prevent plucking with this clay. Just use them once as they need to shrink with the pot during the glaze firing.

[ronfire]

Thanks Min. I will try and make some  " washers" and fire them under the lids, hopefully that will work.

Good memory remembering I use M340.  I guess reclaim clay would be fine to use for them.  I find it does not throw as well but  would have no problems making the   "washers" with it on the wheel.

 

[Sorcery]

8 hours ago, ronfire said:

Thanks Min. I will try and make some  " washers" and fire them under the lids, hopefully that will work.

Good memory remembering I use M340.  I guess reclaim clay would be fine to use for them.  I find it does not throw as well but  would have no problems making the   "washers" with it on the wheel.

 

I feel like you will end up having more problems with these "washers", since you're "treating a symptom and not the problem".

What's the making process like?

Better to fix the making problem IMO.

Something as simple as a rolled rim can keep em true.

Warpage is Molecular.

"Aim small miss small".

Sorce

[Mark C.]

These are not french butterdishes . Not regualr butterdishes either -you pack the butter in bottom?

I'm wondering about the bottom -why it has the tall lip?

If you changed the design they could be fireed as one.

whats the thought?

[ronfire]

The butter is packed into the bottom and is glazed inside and out except  the  under side. The top is thrown upside down like a bowl then trimmed and a knob added, It is glazed except for the bottom edge so it can sit on the shelf.  

I could add a thicker rolled rim on the edge but it is not the look I am trying for.

 

[Hulk]

Hi Ron,

fwiw, I prefer to make (curved lids - flat is different!) lids upside down as well (off the hump for smalls, one at a time for largers), and fire them in set in the gallery or on the shelf, no problems out of round either way (yet). From there, I'll pull and stick a handle, or throw a knob (usually hollow) and stick that. For a small knob, I'll leave a thicker base and just turn it.

Other problems, yes, oops, broke it, a bit too small, bit too big, don't like the profile, don't like the knob, etc. ...which is why I try to follow Bill Van Gilder's advice and always make extra lids and at standard sizes. Will have to move boxes of extra lids to storage soon, else target practice?

So, I'm curious what solves the problem for you - doesn't look (to me) that those lids are so big and heavy that they can't drag evenly as they shrink and end up round. 

Nice shape, btw.

[Mark C.]

Why not leave the gallery unglazed-problem solved -fire them together like most butterdishes-take up 1/2 the space always warp together .No issues-if you have to leave the lid a little unglazed inside no big deal

[liambesaw]

17 minutes ago, Mark C. said:

Why not leave the gallery unglazed-problem msoved -fire them together like most butterdishes-ytake up 1/2 the space always warp together .No issues-if you have to leave the lid a little unglazed inside no big deal

This.

Seems silly to go through all this extra trouble when you can fire them together and avoid all of these problems entirely.  You have to leave the portion making contact with the donut unglazed anyway, might as well fire it on the actual part.  Could even suspend it with wadding if you're really paranoid.

 

 

[Min]

I think this comes down to aesthetics, not about being silly or being paranoid. I don’t like leaving an unglazed ring on the plate part for the lid to sit on, especially when I use a dark glaze on my white clay, it just looks wrong.  Yes it takes more kiln space to fire them separately but for me it’s necessary to get the look I want. I use my slab roller and scrap clay to make the wasters, really doesn’t take much effort. If it looks okay for your style of work then great fire them together, if not then the wasters are a solution to warping lids fired on their rims.

[neilestrick]

I would definitely fire them separate and glaze everything. It'll look a lot cleaner, especially if you're using a white clay . With a dark clay that raw clay aesthetic is much more palatable. Plus if the lid fits well and doesn't slosh around, you'd have to worry about it touching the vertical wall of the base. Just price them accordingly for the extra kiln space.

I really like this design, like a reverse French butter dish. I might have to make a few....

 

On 5/31/2020 at 9:15 AM, Sorcery said:

I feel like you will end up having more problems with these "washers", since you're "treating a symptom and not the problem".

What's the making process like?

Better to fix the making problem IMO.

Something as simple as a rolled rim can keep em true.

Warpage is Molecular.

"Aim small miss small".

Sorce

Open bottom pieces tend to warp, even with a thick rolled rim, and especially if you're working with a body that tends to soften up at glaze temps. And you may not want the look of a thick rolled rim. This is the standard solution to the problem. I use waster slabs for butter dishes, goblets, cake stands, tall footed bowls, etc.