Ok, so it does rarely happen to me that I either choose a wrong gauge of metal or the counterenamel application is too thick or too thin and the enamel does warp.
Recently In one of the books (Linda Darty?) about a method of putting a flat steel heavy plate on top of the enamel as soon as its out of the kiln. (And yesterday I even saw this product in riogrande https://www.riogrande.com/product/steel-firing-press-plate/350035 -a steel piece with a handle for almost 50 bucks!). I was very suspicious of the method and feared it wil marr or somehow destroy the surface but decided to give it a try on some old enamel pieces I had. I cleaned the bottom of a very old iron (and very heavy!) iron, warmed it up on top of the kiln , and then put it on top of the enamel from the kiln.
The result- it did become flat, it didnt ruin the colors in any way, but it cracked a bit each time anyway. So whats the point and what am I doing wrong? Has anyone tried it and had success?
This post was edited by Anna Margolis at December 6, 2017 12:23 AM EST

I am using two spatulas to put in and to remove the plates from the kiln. Using these tools I can flatten the warped plate by gently pressing the hot plate immediately after removal from the kiln.  

I am not sure I understand: you mean you have one spatula under and one over ? How long do you hold it? No cracking occurs?

No, I am using both spatulas to press down from the the upper side. This is a very short action. If you press it immediately still hot and you don't use strong force, no cracking occurs. 

In the past I had a slab of flat limestone to place hot (still orange or redhot) enamels on ,then I put a heavey metal object on to flatten. No problem with cracking.  John Killmaster.

Doesnt the enamel stick to the limestone?

No it doesn't stick since it is rapidly cooling and the stone is not the kind of stone that can be enameled, although I do enamel lava rocks.  You can press it on concrete instead if it's not painted.

I am very, new to enameling.  This is the one thing I'm struggling with....constantly!  I torch my enamel.  I tried flattening but it cracked it.  Using over a mm thick copper.....does it need to be a heavier gauge?  Help!

A heavier gauge will stay flatter, or switch to steel which has less warpage.

 

OK.  I need to do some research on steel as I'm set up for copper.  What gauge do you recommend if I stay with copper?  Thank you so very much for the help!

I just happen to have a very heavy old iron.  Worked like a charm!  Warped on the counter enamel but when I did the first fire of the front I used the iron.  I heard a couple cracks but couldn't find them once it cooled!  Flat as a pancake!!  Thanks!