The old yellowed Lego returns to shine

[LEGO Train 12 Volts]

Hi everyone,
today I would like to share with you my technique to bring back to the original shine of Lego pieces yellowed by the sun.

I tried the technique successfully with the colors: blu, light gray, white ... but I think it applies to everyone.

What you need is: a cloudless sky , a transparent film for food, a brush, a pair of latex gloves, hydrogen peroxide 40% volumes.

Take your Lego pieces (washed, dry and without dust) and after putting on the gloves, with the brush spread the peroxide evenly on the yellowed surfaces (a light layer is needed).
Wrap the treated pieces with the film for food, so that the peroxide doesn't evaporate and remains in contact.
Expose the pieces to the sun (better if the rays are at the zenith) for about 3 hours.

Every 30 minutes you can massage the film to stir the peroxide layer.
After an hour and a half you can orient the pieces by 180 degrees so that the sun also irradiates the other less exposed sides.

At the end of the treatment, after wearing the gloves, remove the film and wash the parts with plenty of water using a small brush.
Dry the pieces with compressed air.

Here you can see my old Lego space baseplate bring back to the origins.

Look also at the blue plates 6 x 16 and 6 x 14, of the set 926

That's all!

[Toastie]

Hi Emanuele!

I always knew that you will eventually venture into chemistry.

Your approach is perfectly well suited to do that job - the pictures are proving it!

May I just add this: You can go much cheaper, when not using a cosmetic or food-safe product, but rather raw but clean material: 5 L of 12% H2O2 solution cost about €10. Type e.g. purux into Google. Or whatever other brand.

You can then submerge the pieces in the solution using a flat bowl type thing. The effect of exposure to sun may be also done by a solarium type of thing. Or any other source of tanning radiation.

And: I suggest to "wash" (= submerged and leave there for an hour) the pieces in wash petrol before going further. That stuff is really cheap as well. It removes any greasy stuff first and allows the H2O2 to "bite" more efficient.

In any case: Your results are very impressive! Very nice: Chemistry@work!

All the best
Thorsten 

  

Edited May 19, 2019 by Toastie
Removed the Chemistry@work link automatically created by forum software - it leads into nowhere. But it is charming ...

[deraven]

Lots and lots of information available on this process.  As Toastie said, you have plenty of options to go cheaper and various other details to the method depending on what you're looking to restore- just google for "retrobrite" and there's a ton of detail an inspiration to help you take your de-yellowing process to the next level!  

[MAB]

It is nothing new, people have been doing this for years. And unfortunately they will re-yellow again.

[LEGO Train 12 Volts]

Correct but the process can be repeated theoretically over and over again 

[MAB]

13 hours ago, LEGO Train 12 Volts said:

Correct but the process can be repeated theoretically over and over again 

No it cannot. Each time it gets more brittle and eventually they will crack.

[Cwetqo]

But if you do it and keep parts in dark afterwards?

[LEGO Train 12 Volts]

I assume the process stops ...anyhow I had to carry out this procedure after 40 years ...I consider it an acceptable time lapse! 

[MAB]

21 hours ago, Cwetqo said:

But if you do it and keep parts in dark afterwards?

It is possible to open up a 40 year old sealed set and still get yellowed parts. I believe that heat is more important than light for yellowing.

 

[Toastie]

9 hours ago, MAB said:

It is possible to open up a 40 year old sealed set and still get yellowed parts. I believe that heat is more important than light for yellowing.

It will also strongly depend on the material used to stain the ABS. This has vastly changed/improved over the years - as has the formulation and treatment of ABS itself. After all ABS, as every plastic material, has its own formulation secrets - there is more than just the ingredients/monomers listed elsewhere.

A rather difficult thing is to stain the (e.g. ABS) reaction soup before/during polymerization homogeneously. Plus they don't only use ABS.

Depending on production time (age), formulation used then, exposure to heat, light, other chemicals etc. may affect the color. A sealed bag may also be not that much of a seal, when either little fractures are present or vapors have diffused/penetrated the thin PE (or the like) bag. Who knows what the story of the LEGO piece in question would tell … after forty years ...

All the best
Thorsten    

[LEGO Train 12 Volts]

1 hour ago, Toastie said:

 Who knows what the story of the LEGO piece in question would tell … after forty years ...

Maybe with a spectrometer or a carbon analysis?

Just kidding ...thanks Thorsten for the deep analysis of the variables!

[TeriXeri]

On 5/22/2019 at 8:58 PM, Toastie said:

Depending on production time (age), formulation used then, exposure to heat, light, other chemicals etc. may affect the color. A sealed bag may also be not that much of a seal, when either little fractures are present or vapors have diffused/penetrated the thin PE (or the like) bag. Who knows what the story of the LEGO piece in question would tell … after forty years ...

Old LEGO sets' bags had little perforated holes all over it so never were truly "sealed" anyway.

[AmperZand]

On 5/21/2019 at 9:33 AM, MAB said:

No it cannot. Each time it gets more brittle and eventually they will crack.

Sorry, MAB, that is incorrect. While the parts may be getting more brittle, that is due to the light and/or thermal degradation the ABS is undergoing regardless of whether and how frequently (or how strongly) you recolour it with H2O2. Please see this analysis. 

What you said about heat also being responsible is basically correct. Heat can also trigger/sustain ABS's degradation. Ideally, one should store LEGO in a cool, dark place. 

 

Edited May 27, 2019 by AmperZand