Well I think I've got the mixture that works for me...
Here's a quick pic of the old VIC20 case after its second 10 hour coating of Retr0Bright...
No patches or swirling or marks of any kind, looks just like it did when it was new...
The results that worked best for me were...
Mix the OXI powder with boiling hot water from a kettle adding the water a tiny bit at a time using one of those ink cartridge refill syringes just enough at a time to dissolve the OXI powder but leaving it as a thick paste and not runny at all.
Wait for the OXI mix to cool down a good bit then add the Creme Peroxide and mix thoroughly (at least twice the amount of Creme Peroxide compared to the amount of OXI mix). leave for about 5 minutes and mix thoroughly once again before applying the past with a paintbrush.
Lay out all the pasted components on a flat even surface and switch on the UV/BlackLight, leave to stand for 8 to 10 hours. It helps to either rotate the pieces or the lamp a few times during the process in order to make sure the UV light reaches all sides/faces of whatever you're trying to de-yellow.
The more yellowed the components are then you may need to repeat the process again until a satisfactory result is achieved. What I did notice though during all of this was that, the mix seem to become ineffective after somewhere between 8 & 10 hours and leaving the coated pieces for any longer does not give any better results.
This is I think due to the chemical reaction having worn off or gone from the mix after this time and so a new coat needs to be applied again (if necessary).
Got to be honest, after my first attempt at just immersing stuff in the Peroxide and showing no results, I did think this whole thing may have been just a wee bit over hyped but now after using the right mix and most importantly (I found) having a source of UV light. I'm now a true believer in Retr0Bright...
Got loads of stuff that need treated now, old Amigas, VIC20s, C64s, SNES consoles and quite a few other bit's n bobs that are about to be given that "new look" once again...
Thanks to every one who helped out here with advice and tips and a special thank you to the guys at the Retr0Bright homepage who discovered this wee miracle in the first place...
The Stuff I Used...
11Watt Low Energy BlacklightCreme Peroxide 12% 40volVanish Oxy-ActionCheers... :pint:
Franko