Black Rabbit

Do modern white bricks still turn yellow?

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No.... direct sunlight will whiten yellowed parts.  I took 40 year old yellowed mint condition classic ABS windows and left them in a sunny window sill... and after a month they became pure white.

Two problems that cause yellowing is the fire retardant they put into ABS plastic for molding LEGO parts, and also MRA... Mold Release Agent... that allows parts to easily be released from the mold when the parts are produced, have both shown to be a reason for yellowing.

Here's a FLICKR thread on results for leaving elements in a sunny window for whitening them....

https://www.flickr.com/photos/vintage-lego-toys/43024863125/in/feed

 

Edited by LEGO Historian

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Will washing the pieces with soapy water (when new; right out of the box) clip the yellowing at least in part?

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1 hour ago, LEGO Historian said:

Here's a FLICKR thread on results for leaving elements in a sunny window for whitening them....

https://www.flickr.com/photos/vintage-lego-toys/43024863125/in/feed

 

 

It doesn't look that white to me - how yellow was it before?


Btw, quoting myself: "But I don't get it, de-yellowing has been done so massively on old consoles/computers, why aren't we seeing stories of all those having re-yellowed?", well we are:

https://www.classic-computers.org.nz/blog/2013-01-15-retr0bright-only-temporary.htm

Same experience as mine, re-yellowing even stored in the dark. So apparently it's the oxidation of the bromide that gets back to the surface that yellows it, and the only solution is to coat the part?

 

I have a naive question though: how much bromide is there in the plastic, and can it eventually all get out, after several de-yellowing?

 

Edited by anothergol

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On 8/9/2018 at 9:15 PM, anothergol said:

 

It doesn't look that white to me - how yellow was it before?

 

He said he noticed some results after a few days.  The process can take weeks.

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If sunlight (UV) eliminates the bloom, that suggests a thermal pathway for bloom.  However, most sunlight imparts a great deal of thermal energy to a substrate (thus causing bloom), and the majority of polymers have trouble with UV light (degradation), suggesting to me that UV light probably doesn't help eliminate the yellowing.  The picture doesn't show much of anything since it seems to be quite yellow to me.

The best experiments to run would be to take three pieces that have bloomed, clean them both with retrobright, then put one in the freezer (also dark), one in the window with UV light, and one in the window inside a box (dark), and put the window pieces under the flow of a space heater.  In this way, you could test the thermal vs. UV (as much as you can since UV imparts thermal energy as well) and try to probe the mechanism of bloom.  Ideally, measuring the bloom quantitatively with something like an ATR-IR or a UV-Vis reflectance probe would be ideal, but those are not really household pieces of equipment.

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White bricks bought directly from Lego's online Pick A Brick in the last 3 years have definitely yellowed (gone off white to be more precise) for me within a few months despite being stored in plastic containers out of sunlight. Not sure how Lego store them before dispatch, but I was under the impression it is in vast warehouses with little natural light, yet I'm sure some white bricks have arrived slightly off white already. I'm talking holding up two rows of 'white' bricks and being clearly able to seethe colour difference. I've come to think of it as inevitable unfortunately. Very annoying when you always try your best to keep things nice.

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I suppose it's possible they weren't perfect to begin with, I often notice shading differences with certain colors, in the same set. Most notably the green Porchse and the red white and blue bi-plane this year. 

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I think heat is a strong reason why. I live in Florida and most of the parts I stored in an insulated room are okay, while most of the models I had to have stored in an uninsulated room have had the discoloration. Plus, models I noticed at the train show from GFLUG members that had been in storage presumably have been the most yellowed.

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My bricks have been in the loft with no natural light for ten years. Nothing has yellowed, faded or even looks damaged. 

I bought a box of mixed bricks from someone who works with my Dad, they were her son's sets, all 20010-2018 sets. The white bricks from the Star Wars sets were all yellowed where they had been exposed. So much so, I can see where the parts were put together from the clean/yellowed contrast.

Something of a shame really. 

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On 7/26/2018 at 11:36 AM, CopperTablet said:

Once the bricks undergo yellowing, just list them on Bricklink as "Tan" :laugh: and use the sale profits to buy some new white ones.

Smart, if slightly morally askewed.

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