Why do LEGO bricks turn yellow?

LEGO bricks are made of Acrylonitril-butadieen-styreen or for short ABS. ABS is very cheap and very sturdy. It is however flammable (they add product against it) and also very sensible to UV-light, oxygen, moist and heat. If LEGO bricks are exposed too much to these elements, they will turn yellow. So best to keep your used LEGO dry, dark,  temperate and preferably wrapped in a plastic bag to keep out oxygen.

But there is  good news for those precious sets that were not kept in that manner.

I recently bought a second had 6339-1 Launch Pad from a woman on a second hand site in "GOOD" condition, but turned out it was completely yellowed. It was not possible to get refund so I started experimenting after looking up stuff at google.

Materials

• Hydrogenperoxide: It is because of my ex that I found out what exactly it was. It is used to bleach hair so if you go to your local Brico, not going to find it. You can get it at stores like Kruidvat or in a pharmacy. As test, I took a 3% Hydrogenperoxide mixture like this one.
• Vanish Oxy: A stain remover. Reacts with the hydrogenperoxide. Can be found about everywhere. You can get it at Kruidvat
• A container: The smaller the better. Perhaps also best to take one in white or transparant so you catch the most UV-rays.
• The sun: You'll need to have a sunny day. UV-rays are a necessity for this to work correctly.
• Time: Count 8 hours for the bleaching process to take effect.

Results

I tested in on a clouded day but I was too anxious to test so went along just to see what it gave.

This is the rest of my materials. As said a 3% hydrogenperoxide mixture and sone Vanish oxy that I first dissolved in a very small quantity of water. I left the bricks to sit in the solution for about 8 hours. During those 8 hours I spooned it every hour about.

Result

So the white bricks did have a noticeable improvement. Grey bricks stayed about the same. But it does work. I will repeat this experiment on a more clear day. Normally saturday is forecasted as a sunny day, but you never know in Belgium. I will also take a 10% solution that I bought at the pharmacy. It is quite alot more expensive (paid 20€ for half a liter) tho so I hope it doesn't differ much from the 3% solution. I do believe the sun is the deciding factor on this one.

The bricks themselves still feel flexible and sturdy, the shape and form seems unchanged.

I'll post another update as soon as I get more results.

If you want the Dutch version go here.

Edited October 7, 201510 yr by Neosphinx