Retr0Bright: De-yellowing or otherwise renewing some life to old, dirty bricks.

Awhile ago I placed a very large order on Bricklink to the Czech Republic for a fair quantity of white LEGO bricks/plates, etc. Some of these I ordered in USED condition to save a good deal of money. However, everyone who has an old collection knows, that among their whites (and sometimes blues and greys), lie the dreaded yellowed/discolored pieces.

The plight is certainly common to any longtime LEGO owner, and until relatively recently was a problem unsolved. Enter Retr0bright (follow the link for the full rundown), the brain child of trial and error and some great minds. Though not specifically minded for LEGOs, the findings still apply as we're all dealing with the same ABS plastic in the end.

The basic TL;DR is this: most ABS plastic (LEGO included) has added chemicals to make it flame retardant. This retardant, primarily the chemical Bromine (Br), was found to be the cause of the awful yellowing/browning of formerly white ABS plastic. The Retr0Bright mixture uses a chemical reaction between Hydrogen Peroxide, An "Oxy" based cleaner (Sodium Precarbonate as an active ingredient), and UV light (Sun or lamps) to reverse this process.

Some of you may have heard or even used this process before, but for those who haven't, here's my explanation/tutorial on how to give those whites new life (or allow you to save some money on those Used Bricklink pieces!)

Things you will need:
-1x 88 cent bottle of 3% Hydrogen Peroxide (The ideal strength for a speedy process is 10-15% for best results, but I was testing here! 3% will work just fine if it's all you can find. You will just have to wait longer.)
-1x 2 dollar tub of my grocery store's OxyClean equivalent (The only thing that matters is the active ingredient, Sodium Precarbonate.)
-1x Re-purposed Vessel (I use a butchered Simply Limeade bottle here for ultimate thriftiness. You can use any vessel really, but make sure it's clear so sunlight can pass through. Also, be sure it is NOT sealed. This process releases Oxygen from your bricks, and this can build up pressure in a sealed vessel)

How to start it up:
1-Pour an amount of Hydrogen Peroxide into your vessel that will give the amount of pieces you're cleaning enough space to float and spin around. I used roughly 1/3rd of my bottle for this test.

2-Drop in half a teaspoon to a teaspoon of the Oxy ingredient into some hot water just to mostly dissolve it, then drop it into your Hydrogen Peroxide. Less is more here. If you add too much, you can damage the surface of your bricks, so really just add a little bit. You can always add more if the reaction isn't occurring.

3-Drop in your LEGOs and shake/stir them around.

4-Leave them soaking in the sun (ideally) or under a UV lamp makes this process take a few hours versus an entire day (or two depending on the yellow-ness of your LEGOs). If using a lamp, be sure the lamp isn't so close as to heat the mixture, as the heat will be problematic to the process.

5-Come back to check on the vessel every hour/two hours and shake it around so as to make sure each face of your LEGOs gets roughly equal time in the sun.

You will know the process is working if small bubbles are forming around your LEGO bricks and floating upward. Check for this at the first hour. If the mixture is dormant, add a TINY bit more Oxy to the mixture and repeat until you are sure the reaction is taking place.

Depending on the yellowing of your bricks, you may need to soak these for as little as 3 or 4 hours (in the sun) or as long as a full day or two. The main rule is patience. Your bricks have taken years to yellow. You can burn a day or two reversing it. KEEP IN MIND, this liquid mixture will only be "active" for about 2-3 days. Up until then feel free to re-use the same mixture on your parts!

fSo onto the interesting part, my own test results!

Here's my test set of pieces. The slopes in the upper left corner are NEW white pieces to show the color difference. These are all from my 15+ year old collection save the 4x8 plate which was part of my recent Bricklink order. I tried to get a variance of shapes but in general tried to pick out some of my worst offenders:

After about a 6-hour soak in the darkness (started this process at about midnight) and about 2 1/2 hours in the sunlight, this is the same set of pieces after being soaked in the Retr0Bright mixture, again the slopes in the upper left corner are NEW white pieces:

Some of the yellowing is still visible on some of the pieces, but in general this process is amazing. I can easily soak these again for another run and I think they'll be indistinguishable from new bricks. If some of your are concerned about printed pieces, multiple tests by others have shown that printed LEGOs survive just fine, and if anything only fade a small amount in cases where the piece was severely yellowed and had to be soaked for a longer time period. Stickers will likely come off of pieces using this method.

There are also people who recommend cleaning your LEGOs beforehand, which I did not (as this was a quick proof-of-concept test). I have heard people running their LEGOs through cool cycles on their dishwashers or individually scrubbing them with toothbrushes or sonic toothbrushes. This really just removes any dirt or material from the LEGO and doesn't affect the chemical reaction.

For some references on others experiences and some other information for those unsure of submitting their LEGOs to chemicals, here are some links I used for background research:

Removing Yellowing from Plastics
LEGO Whitening: A LEGO creation by Eggy Pop: MOCpages.com
LEGO Whitening- Retr0Bright - home - Discussion
The Brothers Brick

This is a mostly copy-paste of a post I did awhile back for my Mobile Frame Hangar buddies, but it's definitely still relevant. I've since used this process to de-yellow a large amount of my old bricks, and the results were a lot better on my second run using a high concentration of Hydrogen Peroxide that you can source from beauty shops.