----- Original Message ----- From: "Brian Lanning" <brianlanning at gmail.com> To: "General Discussion: On-Topic and Off-Topic Posts" <cctalk at classiccmp.org> Sent: Wednesday, February 11, 2009 3:38 PM Subject: Re: reversing case yellowing Peroxide is just H2O2 (water being H2O). You have an unstable molecule with an extra Oxygen compared to water (which is stable). Any heat, major vibration, or even UV light will decompose peroxide into Water and Free Oxygen, the Oxygen combines with whatever discolors the plastic and then goes into solution. Heat isn't used because people are worried about plastic warping I guess (or because the reaction is too fast). If you look on the English Amiga Board (EAB) they have a more detailed recipe including some other chemicals added to speed things up. Contact with metal also decomposes hydrogen peroxide (as the Russians found out with leaky torpedoes on the Kursk submarine a while back), but adding free oxygen to mild steel will just rust the hell out of it in a hurry (so if you have plastic+ mild steel parts you will have issues). The problems I have seen with this method is some pieces do not whiten the same and you have blotches, also some mold marks (swirling caused when the hot plastic is injected into the mold) show up where they were not noticable before. I generaly just wash/scrub yellowed parts with dishwashing detergent with "oxy" on the label, the scrubbing releases some oxygen from the soap and you slightly whiten whatever you are cleaning (and remove dirt as well). It will not make anything yellowed look new, but I just want the stuff clean and a shade whiter. Anything that had yellowed is mostly from a bad mix of UV stabilizer in the plastic (to keep the plastic from turning into dust after years of exposure to sunlight), and the odds it will yellow again down the road are probably good (you just cleaned up the surface and not deep into the plastic). So you will need a coating of UV protectand to keep anything you cleaned looking good. P.S. If you use concentrated peroxide much above the 3% solution you use on cuts make sure you have a face shield, chemical gloves, and some kind of chemical apron unless you want to go blind, ruin your clothes, and mess up your skin for a while.

----- Original Message ----- From: "Chuck Guzis" <cclist at sydex.com> To: "General Discussion: On-Topic and Off-Topic Posts" <cctalk at classiccmp.org> Sent: Wednesday, February 11, 2009 5:09 PM Subject: Re: reversing case yellowing Well you just know somebody will get 30% industrial strength peroxide somewhere (work?). I would not want to get 6-9% in my eye anyway.

On Thu, 12 Feb 2009, Patrick Finnegan wrote: It's readily available from beauty-supply shops. You don't need 30%. 20% or so is good enough. -- David Griffith dgriffi at cs.csubak.edu A: Because it fouls the order in which people normally read text. Q: Why is top-posting such a bad thing? A: Top-posting. Q: What is the most annoying thing in e-mail?

Teo Zenios wrote: I don't know if this is going to work but adding lye (sodium hydroxide) to raise the Ph in the solution might help passivating the iron surface enough to protect it against oxidation. Archaeologists uses this trick when treating iron against oxidation when they conserve their findings. I'll second that suggestion. Safety first! /G?ran

On Thu, 12 Feb 2009, Mr Ian Primus wrote: I asked about how it might work on the SNES's weird yellowing. Someone's working on that. -- David Griffith dgriffi at cs.csubak.edu A: Because it fouls the order in which people normally read text. Q: Why is top-posting such a bad thing? A: Top-posting. Q: What is the most annoying thing in e-mail?