I have found that some of my records that were housed in thick plastic jackets (like the ones that simply vinyl used & the ones that came with the laser discs) causes what some people describe as 'fogging' or 'bag rash'. This effect causes either one or both sides of the vinyl to be blurred. Not only it is unsightly but also cause a swooshing or hissing sound in the background when played. I also noticed that all picture discs that were housed in these sleeves were the worst hit as they came in direct contact with it. I do not know why this happened, I presume that there is a chemical reaction between the jacket & the vinyl. Maybe someone who is an expert in the chemical field can find an answer. There is no known cure for this problem as I have tried many ways of washing them but to no avail. The effect is permenant. I urge all collectors who use these type of jackets to check your lps & picture discs asap. Do not leave it in storage as time will only increase the rate of degeneration.