Interesting concept. I know a fair bit about dry mounting but don't know if any of the same information may apply to flattening LPs. With boards and paper it is always good to use a heavy, flat steel plate immediately upon removing the hot board from the press. This allows the heat to dissapate more evenly and quickly while continuing to be under the pressure of a heavy plate. Without the plate If the hot board cools too quickly and or unevenly it will tend to curve. Also, I'm not sure if they are still available, but Seal used to produce "temperature indicator strips" to quickly and conveniently gauge the temp of the press. These were made at with two colored 'buttons' of some plastic-like material. Each color melted at a specific temperature. They were made for to accomodate the more specialized low-temperature mediums for dry-mounting which would make a mess at higher temperatures. I can't recall the temps they'd indicate. My best recollection is 120 and 160 degrees. It was in the lower range for sure. There is also "release paper" which is a heat-resistant paper with a thick glossy coating of some sort that does not stick to dry-mount medium. It is is non-reactive at high temperatures. It is made to be put between the metal platen and the materials being mounted. You can also do this with a piece of white mounting board since you are not using the messy mounting material. But do check each time you use it that no loose dirt or debris gets embedded in that cardboard or you may be pressing it into the grooves of your LP. The Release paper is very resistant to holding any dirt since it has a somewhat glossy coating to it. I'd imagine that a softer buffer, like the cardboard, and or release paper, between the warped LP and the hard steel platen might be safer for the grooves. Keep it clean though!
Neat idea...good luck!
Marco
Neat idea...good luck!
Marco