Wednesday 20 April 2011


Like any long-time LEGO builder and collector, I have my fair share of bricks which are damaged and well past their best. A few are actually broken - spokes snapped off T.V. aerials, leaves broken off plants, plates snapped in two - but the majority are just discoloured.

It's well known that LEGO bricks can become discoloured over time, taking on an increasingly yellowish tinge. This phenomenon is not specific to LEGO, and appears to be related to bromine-containing flame retardants which are added to some plastics for safety reasons. These flame retardants react with ultraviolet light (natural or artificial) to release reactive bromine molecules which initiate a chemical reaction in the plastic causing the hated discolouration. The process of discolouration is dramatically accelerated by prolonged exposure to sunlight. I can recommend the interesting Retr0Bright website as a resource if you're interested in learning more about this phenomenon.

Anyway, for a long time it was assumed that the discolouration process could not be reversed. I was therefore surprised and delighted to stumble upon a number of online accounts of people having some success in returning their plastics, and more specifically their LEGO, to its former glory. While the specifics of the actual restoration process varies from account to account, there seem to be a few common elements. All the reports I've seen basically involve adding a strong oxidising agent (hydrogen peroxide) to a catalyst (tetra acetyl ethylene diamine, or TAED, commonly found in laundry boosters such as 'Oxy' or 'Vanish'), immersing the discoloured LEGO into the resulting mixture, and somewhat ironically bombarding the whole lot with more ultraviolet light, either by sticking it in the sun or putting it under a U.V. lamp. Some of the results do indeed appear to be remarkably good (see for instance the account on The Brothers Brick website), so I figured that I just had to give it a go.

My first effort was a total failure. I mixed some 6% hydrogen peroxide bought from the local pharmacy with some Vanish laundry booster powder, poured it into a transparent Pyrex dish, added the sickly LEGO, and stuck it outside in the weak English winter sun. After a few hours nothing had happened, so I left the ghastly concoction for the whole day, and when there was still no change, I just walked away and left it for a whole week. And despite this, still no improvement ! Thoroughly unimpressed, I put the failure down to a combination of (1) the peroxide not being concentrated enough, (2) not enough U.V. from the low winter sun and (3) it being too cold outside. And I gave up.

Anyway, I recently bought a few old sets from eBay and was dismayed to find that many of the pieces were badly discoloured. Given that the sun was out at the time and it was nice and warm, I figured I'd have another go at LEGO restoration. This time I managed to source some 9% hydrogen peroxide (more concentrated than before, but still not the 10-15% recommended by the Retr0Bright folks). I once again added some Vanish powder to the peroxide, mixed it up as best I could, and poured the mixture into a transparent Pyrex dish. Then I added the LEGO, and placed the dish outside in the warm sun. And I waited. I have have to say that after a few hours of waiting there was little if any change evident. Frustrated, I played my final card. I boiled the kettle and poured half a cup of boiling water into the mix, figuring that perhaps some heat might drive the reaction. The effects were dramatic - within moments, the mixture started to froth, and soon copious volumes of foam were issuing forth from the Pyrex dish and spilling out over the patio and beyond. At this stage I figured the wisest thing to do would be to just leave well alone and not interfere any more lest I cause an explosion. So with some choice words from my wife ringing in my ears as she inspected the state of our patio, I quickly removed myself from the scene......

I returned a few hours later to inspect the damage. Thankfully the chemical reaction I had managed to induce had ceased, and all that was left was a (fully intact, I might add) Pyrex dish containing cloudy liquid and some LEGO. I gave the LEGO a good rinse and sat down to inspect the fruits of my labour.

In presenting the results, I must first apologise that I didn't necessarily plan to share the outcome of my experiments, so I didn't take pictures beforehand. What I've therefore done is attempted to find appropriate pieces to compare with so you can see what happened. So, first off - a red 1x2 brick. This had significantly darkened in colour due to prolonged exposure to light. Below you can see a picture of the 'treated' LEGO on the right, compared with a standard brick on the left (click to enlarge)

Not in my wildest dreams did I expect the result I got..... The treated brick is now toast - pink and badly faded. Interestingly, the underside of the brick looks normal. It's as if only the parts of the brick that were initially sun-damaged have reacted, and sheltered aspects of the brick have been seemingly unaffected by the bleaching process.

Below is a treated yellow brick, shown above a standard yellow brick :

Again, the sides of the brick have been badly faded by the process, but again, the underside of the brick is unaffected. For the record, my experiments also badly faded some medium blue pieces.

As well as nuking pieces in various colours, I also seem to have invented a new shade of grey...

On the left is good old-fashioned 'old grey', on the right is the newer blue-grey ('bley'/medium stone), and in the middle is....discoloured old grey treated by my toxic mixture !

Finally, below you can see a treated white palisade brick on top of an untreated, discoloured white 1x4 Brick :

Success at last ! At least the whites seem to have improved, which is not altogether surprising seeing as the process has partially whitened all the other colours to a lesser or greater extent..... Interestingly, I treated a large, old window with a badly discoloured white surround. The surround was significantly whitened, and the clear window pane survived unscathed.

So the moral of the story ? Well, there certainly seems to be something to this process - there are a lot of success stories out there - but it's clearly not without risk, particularly if you deviate from the suggested method..... Adding boiling water, which to be fair the sources I consulted don't actually recommend, seems to have tipped the balance here, changing a fairly sluggish reaction into something quite violent and damaging. So if you do decide to have a go at treating your own LEGO, think twice before adding boiling water (!), don't treat any pieces you're not willing to sacrifice, and please be careful (don't try this at home, kids !)


  1. Excellent article Dr.D. I don't do used LEGO any more, but when I did, the biggest mistake I made when bleaching bricks was to put some 9v electrical plates in the bleach mixture. I don't suppose I need to explain to you what happened....

  2. Err, forgive me if I'm wrong, but does it say anywhere that you can use the technique for coloured bricks?! I have always know this tecnique works on white and with better results than you have obtained (Tim Goddard I believe has done it a fair bit). But it would never and will never work on coloured bricks - bleaching coloured bricks... I am disappointed in you Doc.

  3. Apparently works fine with coloured bricks, Ed - check out The Brothers Brick link in the third paragraph above, for example. They got good results with white, old grey and blue.

  4. Yes, but they lie Dr Dave, they lie!...

  5. Ah, the hydrogen peroxide must have reacted with the water. I've heard that it does that. Although, I've never heard that it creates foam. Interesting...
    You are probably very lucky that it wasn't high-test peroxide(rocket propellant grade) or you would actually have had an explosion on your hands!
    It's a pity that it didn't really work, though. Discolored bricks are a great bother.

  6. An old posting but glad to have found it. Our white bricks have a shade of skin pink. I'll try the method, but won't immerse the ones with slickers, obviously!

    1. OK - good luck, be careful, and please let us know how you get on!

  7. This happened to me too...

  8. Anonymous23/1/24

    Omg my reds look the same just using the peroxide and 3 hours in the sun. White worked well.