Contrary to common belief the yellowing on old vintage computers is not in any way caused by nicotine or smoking.
its actually a natural reaction to sunlight and the plastic used back in the day that together initiate a chemical reaction that turns the plastic to a yellow discoloration.
Some clever person found this effect was reversible with the use of hydrogen peroxide and plenty of sun.
In this section I will show you the method I use which I believe has given me the very best results.
There are many ways you can do this and everyone has their own technique but this seems to work well for me and best of all its cheap and gives me great results.
First thing though is to prepare your case removing any electrical components that could get damaged although Badges can be left in place. Then wash it in warm soapy water cleaning the unit up as best you can.
I would highly recommend doing this the night before so it has a good drying out period. For this tutorial I will be using this old Vic 20 Case which is a perfect example of the yellowing process.
My Toolset is simple, Cling film, paintbrush, an old pot and hydrogen peroxide in the form of Bblonde 40% VOL Peroxide Hair Dye.
Lay your cling film down and position your case near the left so once we have applied the hydrogen peroxide you can comfortably fold the cling film over the unit and wrap it. Generously Apply the chemical to the top, bottom and sides of the case ( preferably using rubber gloves ) until you are happy its fully covered. It may be a small bottle but it goes a long way so you should get a good few cases done with your one bottle.
The Final Retro-bright Process Place your case in the best place you can find to get direct sunlight and just leave it to do its job rotating every hour or so. Don't expect instant results this process can take six to seven hours to complete and usually its only the last two hours when you see a sudden colour change. You can do this several times if the results are not perfect it mainly depends on how bad the case is. I have found you need all 3 ingredients for this to work well. The UV's of the sun, Heat and I think the fumes contained in the cling film also help with the process. The pics below show the final result after just 6 hours as I started late in the day.