Removing yellowing from Amigas with peroxide

[tonyyeb]

Originally Posted by Merlin

Here you go....

http://www.maplin.co.uk/Module.aspx?ModuleNo=33124
http://www.maplin.co.uk/Module.aspx?ModuleNo=24245

Looked at those, was hoping for a complete lamp but then I can just get the bulb and a cheapo lamp from Asda.

[Merlin]

Well, the other applications they have for UV are for developing the film for circuit board etching and for security checking of banknotes etc. I would expect both of these to be dearer than the relatively simple solution as above.

Edit: I was right, £68 + vat for this....?!

http://www.c-p-p.co.uk/product/asp/P...87/af/page.htm

Here's another mains one for a tenner, I doubt it will be bright enough though:

http://www.alt-gifts.com/gifts/UV-ba...cl112-4258.htm

[tonyyeb]

Think I should stick to the maplin bulbs and just get a standard lamp to put it in?

[Merlin]

Yes, definitely. Unless you are planning to go offering this as a service, I can't see how you could justify the expense.

[tonyyeb]

Right cheapo lamp and maplin bulb it is then!

[Merlin]

An update:

Lorne is still experimenting over a The Vintage Computer Forums. He has now treated a full case from an Osborne 1 and I attach the before and after pictures, this is an impressive result. Lorne is working out the optimum level of "Oxy" during his experiments and I am pleased that he is getting such good results.

[tonyyeb]

Any incidcation on the best level for the best result yet?

[Merlin]

From work Lorne and I've done so far, I don't think more than 1/8 to 1/4 teaspoon of Oxy per gallon (5 litres) is needed, more than that and it foams up. The TAED is a catalyst, so the more you add, the faster the reaction goes. You don't necessarily want it to go too fast though, because it will foam up like an overflowing washing machine!

TAED is only soluble at 1.5 grammes per litre anyway.

[tonyyeb]

I'm going to start the whitening of my A600 and A1200 keys tomorrow. Got the Maplin 75w equiv. lamp, 30% H202, Vanish Oxy... I think I'm all set!

[Magno Boots]

Good luck Tony.

I would advise you to shake the jar of keys often to allow a 'good spread' of light onto them.

From experience I've noticed that the peroxide/oxy mix has a limited lifespan.
Once the keys stop floating and sink to the bottom, It's time for a fresh refill.

Also, don't wait for the keys to be perfectly white in the jar. They seem to brighten more when they're dried.

Magno.

[laser]

Originally Posted by Merlin

Sorry dude, Lorne over at Vintage Computer Forums disagrees with your heat theory; he lives in Arizona and heat isn't a problem there. Heat alone doesn't cut it; UV is definitely required.

Read the later posts in this thread:-

http://www.vintage-computer.com/vcfo...light=peroxide

Lorne is working to optimise the process and he has proved to himself that UV is needed, the UV photons destabilise the co-ordinate bond between the oxygen and the Bromine in the flame retardant (the bond isn't strong enough to be a covalent bond, so it has to be shared electrons between the oxygen and the bromine). No UV, the parts only get wet.

Using bleach to remove the yellowing is only replacing Bromine with Chlorine from the sodium hypochlorite in the bleach; Bromine and Chlorine are both Group VII elements (Halogens) and have one free electron space in the outer orbital. The Chlorine is higher in the Halogen series than Bromine and hence displaces Bromine as it is more reactive. Some yellowing will still occur, as Chlorine will share electrons with oxygen atoms in the same way Bromine will, via a co-ordinate bond.

Please feel free to disprove my theories on this, as long as you can provide some kind of logical chemistry argument to back it up.



Merlin

I don't care about what Lorne says...who is Lorne? a scientist?
I say what I think and what I experimented....
UV light does not help to accelerate

it's not very difficult to understand that heat is the best accelerator because when the liquid is exposed to severe air heat......
that means accelerated with a stove which produces warm air.....the h202 start immediately to bubble......so the reaction is ready fast

bubble = h202 reaction

there's no rapid bubble reaction using any kind of UV light...I tested that

[DDNI]

@ all

[tonyyeb]

What is the best container for this process? An old white ice cream tub? Is the object to imerse the plastic in the liquid or get the light onto the surface?

[Magno Boots]

Immerse the plastics in the fluid is correct. As said, they'll float to begin with, hence give them a good shake often.

I've used a large glass pickle type jar as the keys will get light from all directions. The only downside is that you'll have to flip the space bar every so often.

BTW.. where did you obtain your peroxide?
I couldn't find anything stronger than 9% unless bought in 5ltr or more (at a price exceeding a new keyboard and case!)

[DDNI]

I know that Sally Hairdresser supplies carry 18%. I think Tony works in a college with lab facilities ...

[tonyyeb]

Originally Posted by Magno Boots

BTW.. where did you obtain your peroxide?
I couldn't find anything stronger than 9% unless bought in 5ltr or more (at a price exceeding a new keyboard and case!)

Originally Posted by DDNI

I think Tony works in a college with lab facilities ...

Correct I do. Our science tech is a top bloke who can get me anything dangerous I need.

[Merlin]

I work with 35% H2O2 as well, we treat our trade effluent with it to bleach dyestuffs out before it goes to sewer. Lorne also found it as something called 'Urine Rescue' for removing the odour of pet urine, he got that in 5 gallon containers and it contains 20% H2O2.

BTW, plasticene works for weighting items down. You can also use fishing weights and line to stop things floating in the tank while it's being cleaned.

[DDNI]

Originally Posted by tonyyeb

Correct I do. Our science tech is a top bloke who can get me anything dangerous I need.

H2o2 is indeed dangerous if heated.......
I was asked for ID when trying to buy it in Belfast.


Maybe Laser could test and see what happens when you heat it to say >70'C ....

[tonyyeb]

So can someone describe the optimum process from start to finish? Equipment, ideal environment etc... We need a definative guide I think... well I do! I dont want to waste anymore H202!

[DDNI]

Tony hre is a very interesting page on H202 bleaching...

http://www.acrylikey.co.uk/bleaching_ivory.html