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.
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.
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- 15 posts total
- 15 posts total