I have a modest album collection, with a good number of older albums that have embedded dirt. One that I played recently, Pink Floyd Meddle, was so bad I had to investigate. First I cleaned it in the "Spin-Clean" (a device for scrubbing records) then I put it under the Nikon stereo microscope and the dirt is still clearly visible. I tried rubbing the dirt with my finger, a carbon record cleaning brush and 150 PSI compressed air, the dirt does not come out. If I'm careful and use a tiny pick, I can lift the speck of dirt out of the groove. I read about using wood glue to lift the dirt out of the grooves. Has anybody tried it? Results? The dust particles I have look much like the picture below, except they span the entire groove and are really stuck in there.