Detlof, that is a very interesting situation that has happened to you. I am not certain I have any better explanation, but would like to offer the following.
Usually, only the best new releases, such as the 45 RPM reissues from Classic Records, do not benefit from a cleaning with the RR fluids. Perhaps the extra care afforded to these specialty LP's make cleaning either unnecessary, or at least (in some cases) less important.
Perhaps the old LP you had was pressed differently on one side, as you suggested. Another more likely situation is that it was overplayed. When that LP was new, and popular, many people were still using Scotch tape to fasten coins to the turntables tonearm. This was often the remedy when a new stylus was needed. It would only require one time with an auto play turntable left unattended to destroy the delicate material. I know of times in my youth when families left an LP on as background music, letting it play for hours on the same side. A brand new turntable with the best cartridge will damage an LP if that policy is followed. Back then, it would take little more than once with a coin taped in place.
Please continue to test, especially with newer and more predictable pressings. The RR fluid is manufactured from lab grade water, and VERY little cleaner. The active ingredient is carbon based, and contains no alcohol, detergents or lubricants. If properly vacuumed (VPI) I cannot imagine that there is much left except the vinyl surface.
It is possible that the LP was treated with a silicone spray or cloth (popular long ago) and the through washing removed all the coatings that had accumulated. In theory, that should have provided an improvement, but as with all things in high end, the strangest things do happen. Please keep us up to date on your progress, and thanks for sharing the test results so far.
Usually, only the best new releases, such as the 45 RPM reissues from Classic Records, do not benefit from a cleaning with the RR fluids. Perhaps the extra care afforded to these specialty LP's make cleaning either unnecessary, or at least (in some cases) less important.
Perhaps the old LP you had was pressed differently on one side, as you suggested. Another more likely situation is that it was overplayed. When that LP was new, and popular, many people were still using Scotch tape to fasten coins to the turntables tonearm. This was often the remedy when a new stylus was needed. It would only require one time with an auto play turntable left unattended to destroy the delicate material. I know of times in my youth when families left an LP on as background music, letting it play for hours on the same side. A brand new turntable with the best cartridge will damage an LP if that policy is followed. Back then, it would take little more than once with a coin taped in place.
Please continue to test, especially with newer and more predictable pressings. The RR fluid is manufactured from lab grade water, and VERY little cleaner. The active ingredient is carbon based, and contains no alcohol, detergents or lubricants. If properly vacuumed (VPI) I cannot imagine that there is much left except the vinyl surface.
It is possible that the LP was treated with a silicone spray or cloth (popular long ago) and the through washing removed all the coatings that had accumulated. In theory, that should have provided an improvement, but as with all things in high end, the strangest things do happen. Please keep us up to date on your progress, and thanks for sharing the test results so far.