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After watching several videos on #retrobrighting techniques, I started a couple of small-scale experiments to see if my setup works.
This year's Christmas decorations will shine in UV light! 
If you followed my A3000 restoration threads, you can easily guess which yellowed plastic I need to retrobright 
https://mstdn.io/@codewiz/113586277421694238
This cheap PC keyboard will go first to test the effectiveness of my #retrobrighting process.
The very first step consists in a bath in dish soap and hot water. This should prevent grease and other dirt from blocking the UV light and the ozone.
While I was at it, I also threw in the PCB, just to see if my soap is safe for electronics.
Then I rinsed everything with fresh water and wiped with 70% isopropyl, which didn't seem to disturb the key engravings.
Many #retrobrighting videos dip the plastic to be treated in concentrated hydrogen peroxide, or coat it with hair bleaching cream, which may contain other chemicals.
But 12% peroxide is kinda expensive, and I couldn't find any in nearby stores. The fastest delivery I could find wouldn't arrive in time for Santa to admire my first retrobrighted keyboard.
So I decided to try an alternative: sodium carbonate. Pure and natural since 1874... and dirt cheap at $0.10 per ounce!
I'm no chemist. Until yesterday, I didn't even realize that washing soda isn't the same of baking soda (sodium *BI*carbonate).
But I suspect what was actually needed was sodium *PER*carbonate! 
https://en.wikipedia.org/wiki/Sodium_percarbonate
Wikipedia confirms that, in water, percarbonate decomposes into hydrogen peroxide. Which is why it works the same for #retrobrighting.
But I don't have any percarbonate at home, and it won't arrive before Dec 29 either.
Moreover, how much would I need to get the equivalent of 12% peroxide? Now I regret not paying enough attention in #chemistry classes! 
Before realizing that sodium percarbonate was actually what I was supposed to use, I started a small AB-test in my UV chamber using plenty of sodium carbonate.
After spending about 12 hours dipped in the solution, the '+' key (treatment) is visibly less yellow than the '-' key (control).
Despite using the wrong #chemistry, my first #retrobrighting experiment didn't completely fail. Can anyone explain this surprising result?
I also bought a Sterilite storage box large enough for the A3000 keyboard. I believe it's made of polypropylene or polyethylene, which shouldn't block UV too much, but since my led strip is IP65, I figured I can just hang them on the inside of the lid.
While waiting for one gallon of 12% hydrogen peroxide from Home Depot, I started another #retrobrighting experiment with concentrated sodium carbonate solution, just on a larger scale than the minus key.
While the #chemistry is the same, the conditions are quite different:
- I had to weight the plastic to keep it from floating: will the covered areas look different?
- The same UV light source is being diffused in a much larger environment
- 5W of light won't keep this larger reactor warm, so I moved my electric room heater next to it
- This cheap box doesn't have a gasket all around the lid. Will it quickly vent out the radicals produced by peroxide decomposition in UV?
My second #retrobrighting experiment with sodium carbonate for 24h ended with a slightly paler PC keyboard.
The result is very uneven and the engravings look bleached. I'd call it a failure: don't bathe your vintage plastic in sodium carbonate!
The two controls on the left have been kept outside the box (backspace) and inside, but suspended above the liquid (equals/plus).
Meanwhile, the 12% peroxide arrived, and I poured the entire 1 gal bottle in my #retrobrighting reactor for another 24h session with that poor PC keyboard.
Notice the =/+ key sitting on top of a plastic weight to compare the effectiveness of the reaction in air.
While hydrogen peroxide (H2O2) is commonly used to disinfect wounds and even for oral rinsing, at 12% concentration it must be handled with gloves.
I touched the wet plastic with my bare fingers, and after a few seconds they were stinging, and the skin was already partially corroded. 
I guess that's why you can't purchase peroxide at higher concentrations from retail stores in the US.
The sacrificial PC keyboard turned shockingly pale after spending ~30h in my peroxide bath with UV light.
The +/= key, which was suspended above the liquid, is almost the same shade.
The minus and backspace keys are untreated, while the backslash key was only exposed to sunlight and then UV, but never went in with the peroxide.
Contrary to reports that #retrobrighting weakens plastic, as far as I can tell the material remained strong and normally flexible.
The finalized process appears to be safe enough to start treating our venerable #Amiga 3000 keyboard.
Apart from the space bar, the keycaps don't need #retrobrighting. A good wipe with Windex will do.
Before proceeding, I dipped the plastic shell in dishwasher soap and warm water for 15 minutes. This should remove any grease or dirt that might block our reaction.
As an extra precaution, I'll start off with the keyboard case suspended above the surface of the peroxide.
The +/= key has shown the effectiveness of the alternative dry process, which is also said to yield more even results.
I'm kinda concerned that my UV led strips might illuminate things unevenly, so I'll come check every few hours and rearrange the parts if necessary.
After 48h of dry #retrobrighting at room temperature, my #Amiga 3000 keyboard was still yellowish, though a paler shade than before.
The space bar has an uneven gradient of yellow, suggesting that this air-gapped process doesn't guarantee uniform results.
Oh no! My box is too narrow to dip both halves of the keyboard shell side by side, and the peroxide level is too low to cover them together.
I can't leave it like this if I want a uniform #retrobrighting result...
I exposed the reactor core once again to rearrange the parts.
Now the front part is face down, fully covered by peroxide but not lit by UV. Will it still get brighter this way?
The bottom part is still half covered, and will need to be flipped every few hours.
I could just add tap water to rise the level, but it would also dilute the solution, and I still want to #retrobright the #Amiga 3000
front panel and the mouse later.
Rising the level to cover the keyboard without diluting the peroxide wasn't hard after all. Thanks to @RegGuy for suggesting this. 
While I was at it, I also poured hot water into the jars to speedup the reaction a little.
It's time to prepare the #Amiga 3000 front panel and the shell of the "pregnant" mouse for #retrobrighting.
As before, soak the parts in warm water and dish soap for 15 minutes, then rinse in the shower.
@codewiz Does that require having to get into the shower naked with the Amiga parts? 
@amca I kinda expected a Rick Roll, but this is almost worse 