If you're an audiofile purist, don't read any further. What follows is not for the faint of heart and beyond anything you've seen before. If you decide to continue, please don't comment about how you think it will ruin records until after you try it. Then, if you still feel my method is flawed, I'd love to read your critique.
If you follow my instructions, you'll have to work hard to screw things up. It's really not that scary once you get into it.
I've spent an entire career designing, developing and patenting metal, engineered plastic and vinyl products. I know plastics, their strengths and weaknesses. I also know how to fix things. This is one of those fixes.
I'm also not responsible for any disasters that might befall you. If you try this and somehow manage to screw it up, don't blame me. Use caution and common sense. It works for me and that's all I can attest to.
That being said... Let's begin:
Hopefully, most records you pick up at yard sales, Goodwill and flea markets can be brought back to new using standard cleaning methods. This is only for those discs that still have elevated levels of pops and clicks due to physical damage due to accident, neglect or abuse.
The record in the first photo is one such case. When I pulled it from the jacket, I could see immediately it had gone through a rough life. Under the microscope, the grooves were embedded with crud and the lands (the space between the grooves) showed signs of extreme wear with hundreds of vinyl "deflections" along the edges of the grooves.
Step 1: How Records Get Damaged
Dirty records can be cleaned, but damaged records will still sound terrible no matter how much you clean them. The first image is a microscopic view of a scratch across Skeeter Davis' "End Of The World"... Appropos for 2012, don't you think?. When a record player gets bumped or someone gets careless, the needle skips crosswise over the grooves, literally carving a path through the soft vinyl.
The vinyl being cut away has to go somewhere. Some of it ends up on the needle, some of it ends up as crud at the bottom of the groove and some of it is pushed out of the way, piled up like snow in front of a plow. It's pushed above the surface of the lands and the side walls of the grooves. This is what causes the "tick, tick, tick" you hear after a record has been scratched. The needle is bumping into these deformations and serenades you with it's rhythmic beat a little over 33 times a minute.
The second microscopic image shows a smaller scratch as well, but it also shows many deformations on the edges and sides of the grooves. Back when this album was popular, tone arms and needles were both heavy and large. As they ran through the grooves, the needle would build up up heat, softening the plastic, making the vinyl more prone to damage. A large needle can't fit all the way into the groove, so it rests in part, on the outside edges of the groove.
The edge is the weakest part of the groove, so when a needle vibrates back and forth, it slams against the warm edge, wearing it away, pushing and deflecting vinyl into small mounds above the record surface. The vinyl that's pushed up and out, leaves a pocket behind, and the edge eventually becomes lined with pits and piles of vinyl. The edge begins to take on a new shape as the needle wears away at it, distorting the sound as well as adding pops, clicks and ticks.
Today, needles are smaller, lighter and go deeper into the groove where the vinyl of these old records is still virgin. With a good cleaning, the sound will be rich and pure... Unless your record is still making popping sounds, has visible scratches and glitters like a field of diamonds under a microscope.
If this is the case, chances are, it could use a good sanding.