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@TheLegomane you are welcome.  The third part of the answer is in order to know if they are safe, one would have to know what the compounds in the brick are.  Since these bricks are likely proprietary, the formulations are unknown to the public, so there is no information from which to draw conclusions.  Sorry there is not a better answer.

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This question is for @Grover

I have been brightening Legos for years now with Hydrogen Peroxide with good success.  I submerge the Lego pieces in a glass container with a glass sheet covering to keep the Legos under the solution top.  I started with 3 to 4 hours at first but over the years have found that a full two 8 hour days gets the best results.  I recently ran into a problem, though.  Using the same concentration (3%) hydrogen peroxide solution, same container, and same time length in the sun (2 days) I ended up with over "bleached" bricks.  I was working on an old gray (pre 2004) batch.  They are now mottled gray with very light gray patches and some are almost white.  Even weirder is that a small handful stayed the original old gray. Since the Lego is the same color all the way through I did not think this was possible.  I have heard/seen where an edge of a Lego brick that is not properly submerged will have a whiter demarcation for the bit above the liquid (I forget the technical term for this) but this happened to most of the pieces even those totally submerged.  Obviously, there are some Lego overlap patterns but I don't think that caused the bleaching.  I try not to crowd them but if they have overlapped/touched in the past the worst case was a spot where the yellowing was not removed and the Lego piece had to be redone.

As a chemist, can you think of a reason this happened?  Or, any way to reverse this.  I hate to throw away 1 lb of old gray parts as they are getting harder to come by.

Thanks,

kat-knapp

compressed.JPG

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First, I will stress that this is all speculation on my part since I don't know what the dye used back then was, nor do I know what the flame retardants were.  That being said, there are a lot of possibilities:

• The sunlight is uneven.  Maybe shadows, the sunlight moving around in the sky, higher UV than usual, etc.  Use of a UV lamp would alleviate this problem or at least eliminate it as an issue.
• The unevenness almost looks like a pattern to me.  Either there was something covering it partially, or for part of the time, while it was undergoing reaction (and this would include air bubbles), or perhaps there was a coating of adhesive or something on the bricks that masked that portion
• Lego could have changed the dye and/or the flame retardant over the years.
• These bricks may have been treated previously, or been subjected to unknown temperatures or conditions.

If you're using the same brand of chemicals, it may be worth figuring out if the manufacturer has changed anything (doubtful).  If you use a plastic tub to clean in, UV light may be degrading that plastic and leaching out plasticizer or flame retardant from that container that mixes with the slurry you have up top and creates weird mottling or masking.

To me, the low res pic looks like the sun hit it unevenly.  That's a hard thing to change in solution, but you may be making thin films of the material between the bricks and the glass.  The light grey and white are probably the easiest to see it on.  I'm not sure that I have a lot of suggestions, other than using a glass tub, using a UV source, and making sure there's no overlap there.  It's not an easy thing to figure out, but that's what I would try first.  Good luck!

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Posted (edited)
2 hours ago, kat-knapp said:

This question is for @Grover

I have been brightening Legos for years now with Hydrogen Peroxide with good success.  I submerge the Lego pieces in a glass container with a glass sheet covering to keep the Legos under the solution top.  I started with 3 to 4 hours at first but over the years have found that a full two 8 hour days gets the best results.  I recently ran into a problem, though.  Using the same concentration (3%) hydrogen peroxide solution, same container, and same time length in the sun (2 days) I ended up with over "bleached" bricks.  I was working on an old gray (pre 2004) batch.  They are now mottled gray with very light gray patches and some are almost white. 

I remember seeing a recent Bricktsar video where he left old transparent parts in the sun for much longer then intended, many of them turned milky white.

First 2.5 minutes of the video.

 

 

Edited by TeriXeri

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6 hours ago, kat-knapp said:

... can you think of a reason this happened? 

I have seen the streaking with light gray as well. And I recall seeing images from someone else who noticed that the streaks were actually in the brick before the treatment, but the difference in colors was so subtle it was not noticeable under normal light.

So it may be that the chemicals causing the yellowing are not evenly distributed on the surface? Or not evenly mixed into the plastic?

I wonder if it also happens to white pieces but just is not noticeable because they are white?

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Thank you @TeriXeri  @Grover @62Bricks   All of your responses were very helpful.  I am using only glass containers but I think it was just in the sun too long this time or rather too long in our Florida summer sun vs. the shorter cooler winter sun when I did it last.   

I'll be more careful next time.  I'll keep these separate and see if they revert back after awhile and post if they do.

Thanks,

kat-knapp

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On June 2, 2019 at 4:02 PM, kat-knapp said:

This question is for @Grover

I have been brightening Legos for years now with Hydrogen Peroxide with good success.  I submerge the Lego pieces in a glass container with a glass sheet covering to keep the Legos under the solution top.  I started with 3 to 4 hours at first but over the years have found that a full two 8 hour days gets the best results.  I recently ran into a problem, though.  Using the same concentration (3%) hydrogen peroxide solution, same container, and same time length in the sun (2 days) I ended up with over "bleached" bricks.  I was working on an old gray (pre 2004) batch.  They are now mottled gray with very light gray patches and some are almost white.  Even weirder is that a small handful stayed the original old gray. Since the Lego is the same color all the way through I did not think this was possible.  I have heard/seen where an edge of a Lego brick that is not properly submerged will have a whiter demarcation for the bit above the liquid (I forget the technical term for this) but this happened to most of the pieces even those totally submerged.  Obviously, there are some Lego overlap patterns but I don't think that caused the bleaching.  I try not to crowd them but if they have overlapped/touched in the past the worst case was a spot where the yellowing was not removed and the Lego piece had to be redone.

As a chemist, can you think of a reason this happened?  Or, any way to reverse this.  I hate to throw away 1 lb of old gray parts as they are getting harder to come by.

Thanks,

kat-knapp

compressed.JPG

I'm not sure that this is the issue, but it seems similar to an issue where some of the pieces aren't getting enough sunlight or aren't completely submerged. I saw a technique in a video called burnishing in which you take a flat metal surface and scrape it gently along the surface of the part, which gets rid of some of the white marks. I suggest trying all of the suggestions above before my own, and use it as a last resort if nothing else works as it can scratch the parts a bit.

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On ‎7‎/‎4‎/‎2018 at 8:09 AM, Grover said:

The main problem with any of these methods is that the instruments are pretty expensive (the NMR for instance, is usually around $400k or more, and the 'cheap' instruments, like a benchtop IR, start around $15k), and the methods are time intensive.  No company is going to pay for the time on these instruments and workers time to do the bench work to look for trace amounts of a flame retardant, unless they are a competitor, and in that case, they'd likely keep their results to themselves.  The best we can hope for is that we find a university student with access to these resources and some curiosity--maybe an undergraduate project could do this, or a graduate student studying flame retardants in polymers...

@Grover

That was such a nice read - the whole thread, but particularly your replies/analyses. Really, really nice.

As a physical/theoretical chemist myself, I happen to have I'd say rather well equipped MS laboratories with all sorts of machines and methods - and this at a public university. So the $$ aspect becomes much less of an issue, once we find a good approach and research plan for a BSc or MSc thesis. We do ion/molecule chemistry as one research focus and thus need mass specs to investigate such reactions, i.e. we do basic research. A lot has also to be done "in" the computer as many of these reactions are way to fast and complex to follow them step by step experimentally. As "fall out", we also do develop ionization methods etc. pp. and we work with Bruker, SCIEX, Thermo as well as many other companies.

Lets us assume I like LEGO very much:wink:. Let us further assume I may find a student interested in such work: What do we want to accomplish? Identify the "yellowing" compound for the white bricks would be a good start; would it be a bromine containing compound surviving some sort of ionization (at atmospheric pressure w/ or w/o LC or GC pre-separation using ESI, APCI, APPI or APLI or in vacuum using EI/CI) am sure we'll find it as the isotopic pattern of Bromine almost always tells you if and if how many bromine atoms are present in the compound. I may also ask one of my colleagues/friends in safety engineering - he is a former chief fire officer and now professor for chemical safety and fire defense. I don't know whether he likes LEGO but he does like to research cool things. In one collaboration, we blew up various types of rechargeable batteries - in a controlled fashion of course:tongue: - and tried to identify gaseous combustion products. Was fun.   

However, how do we choose the raw material? From the 1990? 2000? 2010? And how do we find such temporally well categorized raw material? My bricks are all in boxes with certain schemes of categorizing them (e.g. color for the simple x by z bricks), but certainly not according to "year of production". That may thus render such an analysis less interesting, right?

Also, do you think there is any chance to get such information from TLG? For a research project I mean?

Anyway - I would do it as soon as I see a good chance that something meaningful will come out of such an effort.

Anyway here is a link to the MS institute I have founded back in 2011, which is now directed by one of my group co-workers.

All the best,
Thorsten           

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The bromine compound fire retardants used up until the mid- to late-1970s were polybrominated biphenyls (PBBs). After concern grew about toxicity, they were largely replaced by polybrominated diphenyl ethers (PBDEs). These I believe were what LEGO used in the 1980s and 1990s. When they stopped using them (As I believe they have) I do not know.

One could isolate bricks from certain time periods by the mold variation. For example, the old 2x4 bricks without cross supports were largely out of production by the mid '80s. Any yellowed white bricks of this variation would probably date to before 1985. The mold pip began appearing on the studs in the mid- to late-70s, so a white 3001 brick without cross supports and a stud pip would date within that approximate 1975-85 range. One with cross supports would be from the mid-80s or later. Here, one could possibly use the mold markings to narrow down the range, as they changed over time. In the early 2000s, LEGO included a copyright notice with the year on some bricks.

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On 6/20/2019 at 9:05 AM, Toastie said:

@Grover

That was such a nice read - the whole thread, but particularly your replies/analyses. Really, really nice.

As a physical/theoretical chemist myself, I happen to have I'd say rather well equipped MS laboratories with all sorts of machines and methods - and this at a public university. So the $$ aspect becomes much less of an issue, once we find a good approach and research plan for a BSc or MSc thesis. We do ion/molecule chemistry as one research focus and thus need mass specs to investigate such reactions, i.e. we do basic research. A lot has also to be done "in" the computer as many of these reactions are way to fast and complex to follow them step by step experimentally. As "fall out", we also do develop ionization methods etc. pp. and we work with Bruker, SCIEX, Thermo as well as many other companies.

Lets us assume I like LEGO very much:wink:. Let us further assume I may find a student interested in such work: What do we want to accomplish? Identify the "yellowing" compound for the white bricks would be a good start; would it be a bromine containing compound surviving some sort of ionization (at atmospheric pressure w/ or w/o LC or GC pre-separation using ESI, APCI, APPI or APLI or in vacuum using EI/CI) am sure we'll find it as the isotopic pattern of Bromine almost always tells you if and if how many bromine atoms are present in the compound. I may also ask one of my colleagues/friends in safety engineering - he is a former chief fire officer and now professor for chemical safety and fire defense. I don't know whether he likes LEGO but he does like to research cool things. In one collaboration, we blew up various types of rechargeable batteries - in a controlled fashion of course:tongue: - and tried to identify gaseous combustion products. Was fun.   

However, how do we choose the raw material? From the 1990? 2000? 2010? And how do we find such temporally well categorized raw material? My bricks are all in boxes with certain schemes of categorizing them (e.g. color for the simple x by z bricks), but certainly not according to "year of production". That may thus render such an analysis less interesting, right?

Also, do you think there is any chance to get such information from TLG? For a research project I mean?

Anyway - I would do it as soon as I see a good chance that something meaningful will come out of such an effort.

Anyway here is a link to the MS institute I have founded back in 2011, which is now directed by one of my group co-workers.

All the best,
Thorsten           

Bromine and chlorine should be super easy to see via their isotopic patterns as you say, but quantifying them becomes more difficult.  I would think that HPLC would be useful if you could dissolve the material.  I have been reluctant to speculate on the exact composition on here, as there could be some legal issues with various flame retardants, but as @62Bricks says, some of the common flame retardants of the eras we are interested in include PPBs and PBDEs.

My main concern with a thesis project would be the reason for the project.  Is this a matter of detection?  A method development for extraction of flame retardants from plastics for lawsuits, environmentally persistent chemicals, etc. could be a master's thesis, but I'm guessing it's not enough for a PhD.  If, however, the threshold of detection were low enough, you could theoretically do swipe tests for trace quantities, and something like that could be.  It could also be of interest to determine the mechanism of leaching of flame retardants in old plastics, including toys, for environmental concerns, and a PhD thesis could revolve around that.  Trying to determine the mechanism of leaching via UV, thermal, or chemical exposure by trying to figure out if it's a kinetic effect of the flame retardant migrating to the surface due to poor solubility in the polymer or degradation of the polymer could be examined through GPC to see if the MW of the polymer is declining with various stimuli.  You could even run GPC on current bricks made in China and Europe now to see if there is any truth to the 'better' quality plastic rumor that's going around and compare to the old materials.

As for getting the right bricks, you don't really need a lot, so you could get on bricklink and buy an unopened set from a particular era.  Look up when the flame retardants were banned or phased out in Europe and you'll find the years you're looking for.  Pick something solidly in the middle of the years and get a set of basic bricks.  I wouldn't waste time with the sets of actual buildings and such, but you can still find unopened sets of basic bricks from various eras, stuff like this.  Cost of those wouldn't be much on a university budget and a single set would provide a tremendous amount of material for analytical work.

I very seriously doubt you'll get any info out of TLG.  They probably have legal considerations with the flame retardants, so I doubt they'll admit to anything.  Probably best to call the materials 'plastic ABS toys' or something in the paper, too, to avoid legal hassles from the company.  Expanding to other manufacturers, such as Tyco bricks from back in the day, could help as well.  I think old computer keyboards suffer from the same issues, too.  Be aware that the transparent bricks were generally PC, as opposed to ABS, and the more flexible pieces, like trees and flower stalks, were PE or PP.  These may have different flame retardants, but will surely have different bloom.

Edited by Grover

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