Retrobrite science: testing discrete components

[ohaimark]

I read a number of disparate reports on what does/doesn't work effectively for Retrobriting.

I think it's possible to bleach plastic with hydrogen peroxide, but this tidbit from a Wikipedia page is very relevant:

"Hydrogen peroxide is an inefficient bleach below 60 °C, but when activators such as TAED are present, hydrogen peroxide (in the form of the perhydroxyl anion in the alkaline water) can react with the bleach activator in a process called perhydrolysis to form a peroxy acid (also known as a peracid). Peroxy acids are more efficient at bleaching at lower temperatures like 40 °C."

Oxiclean contains both sodium percarbonate (which releases soda ash and small amounts of hydrogen peroxide) and TAED. Thus, I posit, the active ingredient in the actual Retrobrite recipe is peroxy acid of some sort. I also posit that Retrobrite reaction speed does correlate with temperature, especially if one is only using hydrogen peroxide.

I plan to perform a few tests.


1) Denture Tablets
Yes, you read it right. Denture tablets theoretically have everything necessary for a Retrobrite reaction.

"Citric acid, FD&C blue #1 AI. Lake, FD&C blue #2, flavour, polyethylene, glycol, potassium monopersulfate, sodium benzoate, sodium bicarbonate, sodium carbonate, sodium lauryl sulfoacetate, sodium percarbonate, tetraacetylethylenediamine, VP/VA copolymer."

The sodium percarbonate will release small amounts of hydrogen peroxide and the TAED will react with it to form peroxy acids.


2) Sodium Percarbonate
Do you need TAED to achieve functional Retrobrite? Can lower concentrations be used, such as the 3% that a fully dissolved solution of sodium percarbonate achieves? I'll find out. I may also try denture tablets with a sodium percarbonate solution -- their TAED could be useful.


3) Temperature
Does temperature change the speed of Retrobrite reactions?


4) UV Light
If peroxy acids are present AND the water is heated, will the bleaching process occur without UV light? If UV light is present without significant heat, will the process still be accelerated? I have an LED UVA light in the 360-370nm range on order which will help in determining whether UV has an impact -- wouldn't it be crazy if it didn't have any effect? Sunlight may just be donating heat energy through UV radiation and nothing more.


If anyone has a yellowed keycap set of any mounting type that they wish to donate for science, PM me.

[seebart]

Hmm interesting I think I might give Denture tablets a try. First I'll try kbdfr's method:

workshop-f7/g80-5000-mod-questions-t109 ... etrobright

[ohaimark]

kbdfr's method is a pretty standard one that's known to give good results, so long as you prevent drying.

I think the methods I'm testing won't suffer from drying issues -- I'm hoping to use full liquid immersion instead of paint on creams.

[seebart]

Yeah the paint on method is more work vs. immersion. I'm definitely using the good old sunlight.

[kbdfr]

A problem I had encountered with immersion is that you have to prevent things from floating.
The method I use has another big advantage: it is cheap, real cheap
By the way, IIRC, matt3o has a slightly different method where he mixes the oxi stuff and the peroxide cream.

[seebart]

I got the tools ready kbdfr! Waiting for Mr. Sunshine now.

IMG_20160420_193133.jpg (125.26 KiB) Viewed 3307 times

[ohaimark]

A problem I had encountered with immersion is that you have to prevent things from floating.
The method I use has another big advantage: it is cheap, real cheap
By the way, IIRC, matt3o has a slightly different method where he mixes the oxi stuff and the peroxide cream.

The easiest solution to floaters, as it were, is taping weights to the side of the case that you aren't exposing to light. I'd hold down ABS keycaps using clear plastic wrap with holes placed in strategic locations to allow for solution inflow and outgassing. Diffusion would take care of the rest.

I think my methods, if they work (big IF) might prove equally as cheap, if not more so. Isolating the active ingredient of Retrobrite seems like a good idea. Then we can target whatever that compound is.

[E3E]

For Alps, itzmeluigi and I have used Alps clone boards with plastic plates for retrobrighting caps, and it works well. No need for submerging with that method either. Submerging takes a lot longer than a spray, but it a bit less risky of bleaching unless your caps float up.

Also, I hate the cream. Combined with the really powerful UV light I WAS using before I got an LED UV lightbar, I was bleaching caps left and right. It stained like crazy. Worked well in sunlight, not so much under a strong 100W fluorescent UV wash light. My fault there, maybe. I wanted to get a powerful blacklight. Maybe it was TOO powerful.

The UV lightbar takes longer, but seems as gentle as natural sunlight and also has better coverage.

I think the strength of the UV is really what caused such bad bleaching on some runs. So as a lesson: don't use a strong UV light. Use a less powerful one with wider coverage.

[ohaimark]

I'm using a specialized 10 watt LED light, which is going to be pretty darn powerful and provide very high UV output.

I may need to add a diffuser, but the gigantic aluminum pan I purchased should bounce the UV light around like crazy once I make a cardboard/aluminum foil cover for it.

Edit: the Alps clone plate is an excellent idea.

[ohaimark]

Stuff is starting to roll in. I also found out that one can create peracetic acid using vinegar and hydrogen peroxide -- that will be another test option.

Edit: experiment 1, which is sodium percarbonate using a 365-370nm 10w LED light and no heat, has started.