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Flattening warped lp's with Seal dry mount press

I've been meaning for some time to try a test flattening warped lp's with my Seal dry mount press. A recent purchase of two warped White Stripes lp's & the recent tread that Albert Porter & others have had about the topic prompted me to start an experiment. For the first test, I placed a warped 70's Columbia pressing in the press between a 1/2" tempered glass plate and a 1/4" thick acrylic plastic plate, setting the thermostat at 165F. I did not pull the press handle to clamp, I just let the weight of the heating platten do the work as things softened. After an hour, the vinyl was quite flat and I let it cool down for the afternoon. While it looked excellent at first glance, there are problems. There is radial runout now, about 1/8" or so. Even worse, there are small hills and valleys in the vinyl surface that set my Grado Sonata wiggling and shaking. Evidently, the heating, pressing, and cooling process is creating stresses that leave things less than perfectly circular and flat. Next, I'll experiment with less heat and longer thermal heating and cooling cycles to see if stresses can be relieved to achieve better results. At this point though, I don't think I'd run out and buy a dry mount press hoping this to be an easy fix. It's going to take some experimentation to see if this will work. I'll post results as I work through the variables.
photon46

Showing 4 responses by nsgarch

nsgarch's avatar
nsgarch
2,524 posts
 
Interesting -- I suggest you do not use the acrylic, but rather two glass pieces (and 3/8" thick should be adequate since the glass is fully supported and you are only applying the weight of the platen. Lower heat would be good too as someone else suggested.

My reason for nixing the acrylic is that it has a large coefficient of expansion, and so as it heats and exoands, it may be carrying the record with it and giving you the radial runout. Then, as it (the acrylic) cools and contracts, it's trying to "scrunch" the record up, giving you all those nasty lumps and bumps. Just a thought.
nsgarch's avatar
nsgarch
2,524 posts
 
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?
nsgarch's avatar
nsgarch
2,524 posts
 
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!
nsgarch's avatar
nsgarch
2,524 posts
 
pdennis -- If you want to try the glass/oven method, use 3/8" thick glass. 1/4" may not provide enough even weight, and 1/2" may not heat and cool evenly. You should also observe the following:

1.) Make sure your oven really goes down to 140 degrees. Many don't. Test it with an accurate thermometer first.

2.) Believe it or not, gas ovens are better (more even heat inside the oven chamber.) If you only have an electric oven, place a large broiler or baking pan on the lowest rack position right over the heating element to avoid direct heating of the lower piece of glass.

3.) Wait until the oven has remained at the desired temperature for a half hour or so to insure even heating. And then place the record/glass sandwich on the middle rack.

4.) For cool-down, don't move anything. Just turn off the oven and crack the door open until everything reaches room temp.
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