Firing Pots With Lids

[Mike.Kelly]

Hello All.  First apologies if this is in the incorrect forum.

I am new to throwing pots and have been working with a local studio who takes care of the firing process for me.  Recently I made three cookie jars that I glazed both the lid and the rim of the jar.  Fully expecting the two items to be fired separately because I would think they would meld together during the firing process.  However all three pots were fired with the lids in place completely joining the two pieces together.  The studio said that this sometimes happens and I now  have  several new door stops.  I was kind of taken back by this.  It was suggested to freeze them and perhaps I could separate them after they have been in the freezer for a while.   it seems to me it would be easier to have fired them separately. 

Can I get a sanity check?  Is this really the process that people follow when firing items with lids on?

Thanks in advance.

Mike

[Min]

It’s not the only way to do it but the most common way is to fire pots with lids in place. Wax resist on any parts that are going to be touching with a small margin, adding a tiny bit of alumina hydrate to galleries if you use porcelain. The pot helps keep the lid from warping and vice versa. Honestly don’t think freezing them is going to pop the lids off if the entire lid is glazed in place. It’s a shame that who ever loaded your pots didn’t notice the glaze on the galleries. One of the reasons people like having their own kilns is so things like this don't happen, or if they do we only have ourselves to blame. 

 

 

[hitchmss]

Min nailed it on the head before I could post. Freezing will do nothing to unstick your lids. The only way a temp change is going to cause your glazed portions to separate is if there was a rapid temp change, and consequently expansion/contraction which would likely break more than your desired area. Short answer, theyre on there for good unless you cut them off with diamond cutting tools. 

[Mike.Kelly]

Thanks for the quick response and yes buying my own kiln is a top priority for me.  Thanks again.

[Chris Throws Pots]

The policy of the community studio I manage is that we fire pieces how we find them. Most people fire with the lids on for the reasons already described by Min, but some others do fire lids separately. If lids clearly look like they'll fuse together with glaze we'll leave an "are you sure about this?" note before loading them. But in general we fire however each artist leaves their work. 

When lids fuse I tell my students they've made top shelf jars... just display them at a height no one will be able to remove the lid and your secret will be safe. Unless you really do have some doors that need stopping. 

[Mark C.]

Lids in my mind need to be fired on the pots. In many atmospheres like gas /wood/salt /soda the pot can warp and the lid holds that in check  .The same can be true in oxidation(electric kilns). The best outcomes is they fit after the fire . When you fire them separately you run the risk that they will not fit well. The learning process and yes its a learning process is how to wax them -how to glaze them and how to make your seat in the first place so they can separate easily .Using alumina hydrate on the lip or lid is the way to do it with porcelain.

Another skill is learning how to remove a lid thats stuck.If its not glazed together you can hold onto the lid and with spice of wood(I use a large piece of bamboo) you gently tap the pot around in. circle . If this does not work I have frozen the piece and then use hot water on the pot (not the lid) to expand the pot and that usually pots the lid free. All these are for non glazed (no glaze runs) issues-if the glaze has fuzed them you have to use diamond grinders with a dremil tool or a combination of torture until you get it off and your chances of breakage are vey high.Use the Chris Idea of a top shelve pot.

Leraning to make seats and lids is a skill just as glazing and firing them is as well.99.9% of all my lids in my over 40 year career are fired on the pot.

[Rae Reich]

Ah, the tap tap tap of releasing lids on unloading day! Even with a fit that is not tight and a gallery and lid that've been waxed well, stoneware especially wants to grab a little. I like to use the handle of an old 4" house painting brush, held loosely. Mark described the technique - just want to add that you hold the pot by the lid Just Above a Table or Your Lap and don't tap on the thinnest part of the neck.

I have known stubborn lids to spontaneously Ping open on the (top) shelf years later!

[preeta]

Mike how did you leave the lids to be fired? We’re they in the pot or next to the pot? 

For our studio if we have glazed the whole lid then the lid sits next to the pot and it is fired that way. However if you don’t glaze the whole thing you leave the lid on the pot. 

In other words things are fired as you leave them. 

[Mike.Kelly]

Yes that's pretty much what happened.  The lid was on the pot and that's how it was fired.  If it was explained that way before or after the pots were fired I wouldn't be as upset.  I was told it just sometimes happens.  I would think a lid and pot that is glazed and then fired would always glaze together :-(   Its not the first trial by fire incident at my local studio and not what I would expect after paying for lessons.  I have learned more from youtube and I am sure now from this community.  Looking for an excuse to buy my own kiln.  I think I found it. :-)

Attended 10 lessons and I absolutely love every minute I get to spend on the wheel.  Electrician has been scheduled :-)  wife took some convincing though.

 

 

[Rae Reich]

Nice chatter!

[Marcia Selsor]

freezing works when a lid sticks but not from being completely glazed. More like the wax wasn't completely covering the area where they touched. It is a shame but studio practices usually fire lids on. It prevents the pieces from warping and not fitting. This should have been part of the instructional info on glazing. 

Sorry you weren't informed.

Marcia

[Mark C.]

In ceramics there are a thousands ways for it to go bad.

Just a bump in the road really

Here is story about lids

My 2nd or 3rd year in ceramics at university I was working as the kiln tec and loading and firing many kilns as a work study student. (it was early 70s)

My instructor /mentor asked me to retire a large lidded for off his. I handled it with kid gloves  loaded it low in kind so as it would not crack in top early heat. I at that time did not think about retires not shrinking but actually expanding as they are preshrunk already. I deck a shelve over the lidded for with fumes to spare (my usual mode of loading glaze fires .

The pot expanded and the lid  top stuck to shelve above with glaze and stayed there. I ruined that pot and learned about expansion of refires all in one swift lesson.

When loading refire allow room for expansion as they get bigger when hot and cool to same size .

School of hard knocks-the best lessons are learned there.

[Rae Reich]

On 4/19/2018 at 6:46 PM, Mark C. said:

When loading retire allow room for expansion as they get bigger when hot and cool to same size .

Whoa - I never knew this, but it makes sense.