Flattening warped lp's with Seal dry mount press

As an addendum to my post, here is one source for some of the dry mounting supplies I mentioned. They don't seem to have the temp indicator strips, but I like Albert's idea better anyway.

The presses themselves can be had on eBay at any given time for much less than new. I own two of them and the smaller, older one is ideally sized for an LP. If this thing turns out to work well for LPs I'll sell it to whoever may be interested for a good price. I no longer have a record collection so it won't serve me in this respect. Keep in mind, in seeking one out, they are a bit heavy to ship, so a local purchase is best. I think the smaller one I have must weigh about 40 lbs.

Marco

My Seal press had a dial thermometer (very accurate I might
add) built into the top platen and the heat was thermostaticaly controlled at any setting. Perhaps this was only on the larger models?

Ok, round two in the saga, much better results this time. Thanks to all for the input and suggestions. Nsgarch, I thought your ideas about the possible problems with acrylic warranted removing it for this experiment. I also thought that if the lp is sandwiched between two pieces of glass, there is going to be a small void between the raised label and the raised rim that might allow the small ripples to form in the groove area on cooling. So I used this material sandwich from the bottom layer up: 3/8" glass, 1/4" paper surfaced "foam-core" mounting board, 2 thick sheets of artists' drawing mylar (smooth sides facing the lp which is between these mylar sheets,) and last, a 4 ply cotton rag mounting/mat board (ordinary mat board would work too.) My thoughts were that the slight deformation of the softer foam core and mat board would cushion and support the thinner groove areas of the lp on cooling. I used my digital darkroom thermometer to make sure that the thermostat was accurate and heated the press to 140 degrees f. I preheated the boards to drive out moisture (less expansion/contraction,) made sure the mylar surfaces that would contact the lp were clean, and then put everything in the press for 15 minutes. No clamping, just the weight of the platten pressed things. After 15 minutes, I turned the press off and didn't open it for 4 hours as it cooled off. I don't think you would want to try and remove the lp to cool under a weight because the vinyl cools, contracts, and warps very quickly when it's soft. By the way, this was a THIN lp, not a thick 180 gr. lp. If you were working on thicker, heavier lp, I'd think you would want to heat things a few minutes longer. This time, everything worked like a charm. The vinyl is perfectly flat, no radial runout, no groove damage. It plays fine with no increase in surface noise or other audible defects. I will repeat this on a few more warped lp's to make sure things are repeatable and predictable and report back. Thanks again for the ideas, Will.

.
Will,

Nice work and thanks for the all of the effort in sharing your results. It will be great to hear how you fare with this in the end.
.
Rgds,
Larry
.

Will, success! However, just to make sure you are not getting unnecessarily complex (with your sandwich) you might just want to try the two-sheets-of-glass thing. I mention this because if it works as well, it makes things a lot simpler, and because two-sheets-of-glass-in-the-sun is the old standard way of doing this -- and it does work, it just takes a lot longer, and of course you need a good sunny day.

On the other hand, it's 108 in Tucson today, so it shouldn't take more than 5 minutes in the sun and 30 minutes out!