yellowed murky plastic

I have a friend who is a major Mac geek (infact his license plate is macgeek) and he used to fill his tube up with cleaning solution and soak old Mac cases and Apple ][ cases for days on end to reduce the discoloration. It all depends on the reason for the discoloration - some are from heat, cigarette/tar residue, others are from sun UV exposure and others were from just the grade of plastic and color mixture (I used to pull virgin Atari ST's out of there boxes and find them discolored, I noted this with some of Apple's platinum line of computers during the "Quadra Years" that the plastics would discolor just from the quality of plastic. Some of the discoloration can be superficial while others go right to the core of the plastic parts. Curt 'Computer Collector Newsletter' wrote: -- No virus found in this outgoing message. Checked by AVG Anti-Virus. Version: 7.0.323 / Virus Database: 267.7.8/22 - Release Date: 6/17/2005