Brick de-yellowing techniques

[Raystafarian]

17 hours ago, Grover said:

Nice work, and thank you for sharing!  The more data we have in this arena, the better versed we will be in figuring out out to solve the yellowing issue.

FYI, the active ingredient in OxyClean is sodium percarbonate, 2Na2CO3•3H2O2.  When you throw it in water, it releases hydrogen peroxide, which is where it gets its oxidizing power.  You essentially made OxyClean (minus any extraneous surfactants that the manufacturer may add) by adding hydrogen peroxide to a carbonate solution.  I'd be curious to know if your method with the base (sodium carbonate) was any more or less effective than the pure 3% hydrogen peroxide solution alone.  I'd be reluctant to start adding bases to the bricks if I could help it.  I would be even more reluctant to use pure OxyClean, as it may contain surfactants that could have interactions with the polymer or plasticizer (or even the flame retardants) in the ABS.  Great job, and let us know if you try any more experiments!

 

Ah, seems I was mistaken on the composition of OxyClean (thanks) - I didn't want to attempt to find it here because.. well it's just hard to come across certain things and I haven't seen it before. I might give it a go with just peroxide if I get any more used bricks that need it.

The plates just seem to have the usual "harder to take apart" from the lack of skin oil from use, but they seem to be doing all right, not seeming more brittle or anything -

 

Edited September 22, 2019 by Raystafarian

[Esoth]

Hello, new to these forums! I've been trying to de-yellow my bricks with hydrogen peroxide and sunlight, but my townhouse's location makes the sunlight hard to achieve. I have tried regular electric light with minimal success so I'm under the assumption that the light from the sun is needed to be a higher frequency to achieve the desired effect. I'm no quantum physicist, but I'm assuming higher frequency light such as ultraviolet is needed for the desired effect. Would typically commercially available black light bulbs likely achieve the desired effect?

[Andman]

As far as i know you need UV light to make the reaction happen. I used 3% hydrogen peroxide and de-yellowed the rims from my 8880. With 3% the process takes longer but is less stressing according to a friend who is working in chemistry industry. So put the rims into it for about a week. Btw due to the process H2O and O2 are created. You can see if there is H2O2 as long as there are O2 bubbles on your parts.

A light bulb would help as long as it emits UV light. I also thought about getting one of these UV light sterilisers with a tray for fluids.

[Pinnacle]

I’m not so sure that (sun)light is the main course of that annoying yellowing of the LEGO-parts. I had a while ago collected a large box of white, pink, light blue and light yellow bricks and put it in a dark corner in the attic. It has been there for at least 20 years because I had the intention to build some fairy-tell castle like a Disneyland castle. But when I wanted to start and opened the box, some of those bricks turned out to be pretty yellowed. But also some not or hardly not. And more strange, some parts were darker than tan on one or more sides, or even half tan and half white op one single side…

I think the problem is more in the composition of the Acrylonitrile-butadiene-styrene (ABS) and the reduced control on it than it has to do with the light. Sunlight tends to make colours pale more.

It is a pity that a product from a company as The LEGO Group can have so many colour deviations and discolourations. You’d expect that more with a cheap Chinese counterfeiter. 

 I'm afraid we have to deal with it. I think that various chemicals will damage your LEGO-parts more.. 

Edited August 3, 2020 by Pinnacle

[Grover]

9 hours ago, Pinnacle said:

I’m not so sure that (sun)light is the main course of that annoying yellowing of the LEGO-parts. I had a while ago collected a large box of white, pink, light blue and light yellow bricks and put it in a dark corner in the attic. It has been there for at least 20 years because I had the intention to build some fairy-tell castle like a Disneyland castle. But when I wanted to start and opened the box, some of those bricks turned out to be pretty yellowed. But also some not or hardly not. And more strange, some parts were darker than tan on one or more sides, or even half tan and half white op one single side…

I think the problem is more in the composition of the Acrylonitrile-butadiene-styrene (ABS) and the reduced control on it than it has to do with the light. Sunlight tends to make colours pale more.

I would assume that the pathway to bloom is likely thermal not UV.  Sunlight puts out a tremendous amount of thermal energy, so the thermal process can be mistaken for UV.  Attics can get notoriously warm, and it doesn't take much to cause bloom in some of the old parts. 

Some of the UV talk here is not about causing bloom but rather cleaning it off.  In this the UV is needed for breaking down the hydrogen peroxide.

[Esoth]

I did some more reading and wavelength widths are mostly classified into UV-A, UV-B, and UV-C in order of lower to higher frequency. Sunlight is more likely to be absorbed by the atmosphere at higher frequencies so black light bulbs (UV-A) I would assume are a good bet. The effect is really a type of bleaching that is common to hair and other treatments. I'm really just looking at an alternative to natural sunlight because my townhouse's location and tree cover make natural sunlight hard to get. I've passed several bricks through many liters of H2O2 but the limited sunlight has left results minimal and somewhat sporadic. The idea of setting up a small tub under a black light sounds like it would offer more control.

By the way, my understanding is the yellowing is a side effect of a chemical treatment TLG does to apply flame retardants. It is not poor quality so much as a compromise in conflicting values.

[jonwil]

This video

shows a technique for indoor restoration (in this case old computers but I suspect the yellowed LEGO might be the same)

[MAB]

On 8/4/2020 at 7:33 AM, Esoth said:

I did some more reading and wavelength widths are mostly classified into UV-A, UV-B, and UV-C in order of lower to higher frequency. Sunlight is more likely to be absorbed by the atmosphere at higher frequencies so black light bulbs (UV-A) I would assume are a good bet. The effect is really a type of bleaching that is common to hair and other treatments. I'm really just looking at an alternative to natural sunlight because my townhouse's location and tree cover make natural sunlight hard to get. I've passed several bricks through many liters of H2O2 but the limited sunlight has left results minimal and somewhat sporadic. The idea of setting up a small tub under a black light sounds like it would offer more control.

By the way, my understanding is the yellowing is a side effect of a chemical treatment TLG does to apply flame retardants. It is not poor quality so much as a compromise in conflicting values.

I've done it on other toy parts using a UV torch, and it is only just into the UV (in fact, a lot of visible purple). Worked fine. I'd try anything that is a cheap UV source first.

 

I imagine the problem is a whole range of effects combined. I rarely have any problem with LEGO yellowing, although mine is never stored on a window ledge and the temperature here is reasonably consistent throughout the year (in terms of no extremes of heat and cold). I have seen other people's collections here that have yellowed where they have been on a window sill or in bright light. It also seems more people in the USA have problems with yellowed LEGO than people here. Whereas I've had it bad on some old electronics and old action figures.

[AmperZand]

On 8/4/2020 at 7:33 AM, Esoth said:

By the way, my understanding is the yellowing is a side effect of a chemical treatment TLG does to apply flame retardants. It is not poor quality so much as a compromise in conflicting values.

It’s a common misconception that the discolouration is caused by bromine additives to the ABS. But that’s just not true. Pure ABS will degrade. UV and/or heat will accelerate the process, especially UV.  See here for an article on the subject.

Per the video linked to by @jonwil above (very cool video by the way - if you’re a nerd like me!), artificial UV light will do instead of sunlight. I haven’t tried it with artificial lights; in the summer months, there is enough sunlight where I live. In addition to H2O2, I highly recommend adding Oxy Action Crystal White. It hugely reduces the time required.

I de-yellowed some Classic Space parts from a 1981 set (6927) in 2014. The assembled set has been stored at room temperature in the dark since then with no sign of re-yellowing. Also, there is no evidence that the parts are any more brittle than if I had left them untreated. None of the de-yellowed pieces have cracked. Then again, the set has remained assembled since 2014, so the lack of cracking may just be due to the parts not being stressed through dis-/re-assembly. 

[Grover]

14 hours ago, AmperZand said:

It’s a common misconception that the discolouration is caused by bromine additives to the ABS. But that’s just not true. Pure ABS will degrade. UV and/or heat will accelerate the process, especially UV.  See here for an article on the subject.

It is true that ABS can discolor through oxidative degradation of the polymer.  However, without knowing the material constituents, it's difficult to state exactly what is going on in the process.

[AndrewH7]

I've some plate with square on underside, built a trailer, =d bricks around the edge, & left on top of freezer where there is window in roof. Found it went whiter, & yellow bricks faded. So how to get them yellow again, more sun'll make them white?

[blavenn]

Maybe we'll all get lucky and Lego will release a de-yellowing set complete with Powered Up UV lights.  Just had to take a few white pieces of mine that were starting to get really bad, outside under the sun soaked in peroxide last weekend.

Edited March 29, 2023 by blavenn

[Toastie]

On 3/29/2023 at 4:21 AM, blavenn said:

Lego will release a de-yellowing set complete with Powered Up UV lights

Well, I don't think so. They are afraid of so many things, because so many people have sued them.

UV lights = bad. Directly look into them and mayhem breaks loose.

H2O2 = incomprehensibly bad: A dangerous chemical. OK, some use it to lighten up their hair color without knowing - but, no way.

So bad x incomprehensibly bad = out of space bad.

But: You can do that on your own, if you want to, as you did.

Best wishes,
Thorsten

[LegendaryArticuno]

On 3/30/2023 at 4:51 PM, Toastie said:

UV lights = bad. Directly look into them and mayhem breaks loose.

Don't forget cancer.