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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.

@codewiz I think the other reason is it's used for making bombs.