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Frank Filz showed me a brick out of a sealed set from the 70's that had
yellowed in the box, once opened over twenty years later. The box may
have been near or in a store window, so it may have gotten UV through
the box, but the parts in the same box that were inside a plastic bag
had not yellowed.
Show what do we know?
- ABS yellows. White, light grey and blue bricks show the yellowing most
visibly.
- Parts yellow with age, but not uniformly. Bricks faces against other
faces do not yellow.
- Sometimes the yellowing can be bleached out, but as Tom Stangl avows,
sometimes no amount of bleach can take the yellowing out.
- Parts do not uniformly yellow, even though all sides are exposed to
air. I have monorail track that is partially yellowed, but was
presumably completely air exposed.
- Parts that get sun exposure yellow faster. This is common lore; can
anyone dispute it?
- Parts in sealed boxes or in wooden drawers can yellow, apparently
faster than parts that get diffuse sunlight.
My theory is that the ABS is reacting with some (unknown) airborne
chemical, and the presence of UV radiation speeds the reaction. That
chemical concentrates in wooden boxes, but I'm no chemist.
It would appear to be prudent to store white bricks in airtight plastic
bags. Maybe ABS outgassing protects itself from the yellowing process.
It would be really fascinating to hear about anyone's experience with
yellowed bricks in old MISB sets. Has anyone found a yellowed brick in a
perforated polybag?
Cary
"Fredrik Glöckner" <fredrik.glockner@bio.uio.no> wrote in message
news:m3itij7ufq.fsf@crossblock.localdomain...
tnt@arnesson.nu (Tobbe Arnesson) writes:
> I have pre dark ages bricks that used to be white too. But they have
> been stored in light secure boxes and such so I have no clue how that
> occured, I suppose it's aging in the plastic.
On the subject of my 5580 Highway Rig which was on display, I clearly
noted that only the visible white parts had yellowed. The parts of the
plates that were covered with other parts, for example, were not
yellowed. This leads me into believing that it's the light that yellows
the parts.
Could it be that your white parts were already yellowed before you put
them into the light secure boxes? Perhaps you did not notice/care about
this effect at the time?
Or it could be that the light exposure to the parts had started a
photographic process which continued during the storage period? This
is, BTW, how photographic paper work. The exposure takes place, and
then the paper is put into a catalyst liquid (aka developer liquid),
which turns the exposed parts black. The paper doesn't actually turn
black during the exposure.
Fredrik
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On Wed, 30 May 2001, Cary Clark (<GE5u0s.MLF@lugnet.com>) wrote at
18:00:14
>
> My theory is that the ABS is reacting with some (unknown) airborne
> chemical, and the presence of UV radiation speeds the reaction. That
> chemical concentrates in wooden boxes, but I'm no chemist.
>
> It would appear to be prudent to store white bricks in airtight plastic
> bags. Maybe ABS outgassing protects itself from the yellowing process.
> It would be really fascinating to hear about anyone's experience with
> yellowed bricks in old MISB sets. Has anyone found a yellowed brick in a
> perforated polybag?
It is distinctly possible that there is more than one cause of
yellowing, as there appears to be more than type of yellowing.
Having said that, the following suggestion covers both removable
(surface) and non-removable yellowing, depending upon the age & exposure
of the bricks.
A prime suspect must be decomposition by free radical attack. Exposure
to light will accelerate this, and putting the bricks in the dark
afterwards will not slow it down again, if there is nothing in the
plastic to scavenge the radicals & stop the reactions. The different
amount of yellowing in different coloured bricks can be explained if
dyes of different colours have different levels of effectiveness as free
radical traps. It could also just be some of the dyes mask the yellowing
better :-)
--
Tony Priestman
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In lugnet.general, Tony Priestman writes:
> A prime suspect must be decomposition by free radical attack. Exposure
> to light will accelerate this, and putting the bricks in the dark
> afterwards will not slow it down again, if there is nothing in the
> plastic to scavenge the radicals & stop the reactions. The different
> amount of yellowing in different coloured bricks can be explained if
> dyes of different colours have different levels of effectiveness as free
> radical traps. It could also just be some of the dyes mask the yellowing
> better :-)
I don't know nuthin bout no free radicals, but my grandfather has had
white vinyl siding on his house for about fifteen years, and its still a lot
whiter than my white LEGO bricks purchased at about the same time (and which
have spent a lot less time in the direct sun than his house). I know the
material itself is different (though it would be cool to have a house with
LEGO siding), but isn't there some way to marry the benefits of the two
plastics? 8^)
Dave!
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On Wed, 30 May 2001, Dave Schuler (<GE62DC.J0D@lugnet.com>) wrote at
21:00:48
> In lugnet.general, Tony Priestman writes:
>
> > A prime suspect must be decomposition by free radical attack. Exposure
> > to light will accelerate this, and putting the bricks in the dark
> > afterwards will not slow it down again, if there is nothing in the
> > plastic to scavenge the radicals & stop the reactions. The different
> > amount of yellowing in different coloured bricks can be explained if
> > dyes of different colours have different levels of effectiveness as free
> > radical traps. It could also just be some of the dyes mask the yellowing
> > better :-)
>
> I don't know nuthin bout no free radicals, but my grandfather has had
> white vinyl siding on his house for about fifteen years, and its still a lot
> whiter than my white LEGO bricks purchased at about the same time (and which
> have spent a lot less time in the direct sun than his house). I know the
> material itself is different (though it would be cool to have a house with
> LEGO siding), but isn't there some way to marry the benefits of the two
> plastics? 8^)
uPVC for outdoor use in windows, etc. is absolutely brimming with the
stuff that stops it going yellow & decomposing. Because LEGO isn't
designed for outdoor use, it probably isn't :-)
(cf. 5 year model replacement cycle at Legoland)
Dunno much more myself, I've just got a friend who's a chemist.
--
Tony Priestman
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In lugnet.general, Tony Priestman writes:
> On Wed, 30 May 2001, Cary Clark (<GE5u0s.MLF@lugnet.com>) wrote at
> 18:00:14
<SNIP>
>
> A prime suspect must be decomposition by free radical attack.
Darn revolutionary extremists! I wish they would leave politics out of this.
:-)
-Duane
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In lugnet.general, Duane Hess writes:
> In lugnet.general, Tony Priestman writes:
> > On Wed, 30 May 2001, Cary Clark (<GE5u0s.MLF@lugnet.com>) wrote at
> > 18:00:14
>
> <SNIP>
> >
> > A prime suspect must be decomposition by free radical attack.
>
> Darn revolutionary extremists! I wish they would leave politics out of this.
Just get yourself some free radical traps. Work like a charm for us, and we
didn't even have to pay shipping.
<grin>
(wait for it...)
It really is pretty elementary.
<duck & run>
James
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In lugnet.general, Cary Clark writes:
>
> Show what do we know?
> - ABS yellows. White, light grey and blue bricks show the yellowing most
> visibly.
> - Parts yellow with age, but not uniformly. Bricks faces against other
> faces do not yellow.
> - Sometimes the yellowing can be bleached out, but as Tom Stangl avows,
> sometimes no amount of bleach can take the yellowing out.
> - Parts do not uniformly yellow, even though all sides are exposed to
> air. I have monorail track that is partially yellowed, but was
> presumably completely air exposed.
> - Parts that get sun exposure yellow faster. This is common lore; can
> anyone dispute it?
> - Parts in sealed boxes or in wooden drawers can yellow, apparently
> faster than parts that get diffuse sunlight.
According to our resident plastics expert at work, both ABS and
CA (cellulose acetate) polymers will discolour from exposure to
ultra-violet light. The UV energy directly "attacks" the molecular
bonds of the polymers. And presumably this damage is cumulative---
in other words, once there has been exposure, the plastics will
begin to discolour over time. I would speculate that this is because
each broken molecular bond releases more energy, further energizing
the reaction, and so on. Technically it's really a long-term
decomposition. Polymers in general have a useful life, over which
their mechanical properties (strength, flexibility, etc.) degrade.
This is hastened by UV exposure.
Compare the areas of your "white" computer monitor cases that
are exposed to light to those that aren't as much---you'll see
it's yellowing, too, if it's old enough.
Also, I was told that ABS should not outgas at atmospheric pressure
unless heated up to it's softening point. Put it into a vacuum,
however, and it's a different ballgame. For example even metals can
outgas in space.
I draw one conclusion from all of this: If your LEGO has ever
seen light, and unfortunately all of it has (at the factory),
then it will yellow. The only question is just how long it will
take.
KDJ
______________________________________________________
Harbinger of LEGO Death #203, Windsor, Ontario, Canada
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Recently I was checking some of my Classic Lego windows & doors for
yellowing. The older ABS white windows (from 1964-72) were quite prone to
yellowing. However, ALL of my Cellulose Acetate white windows had sustained
NO yellowing (I have hundreds of these). I have the feeling that ABS is much
more prone to yellowing than Cellulose Acetate is.
Gary Istok
"Kyle D. Jackson" wrote:
> In lugnet.general, Cary Clark writes:
> >
> > Show what do we know?
> > - ABS yellows. White, light grey and blue bricks show the yellowing most
> > visibly.
> > - Parts yellow with age, but not uniformly. Bricks faces against other
> > faces do not yellow.
> > - Sometimes the yellowing can be bleached out, but as Tom Stangl avows,
> > sometimes no amount of bleach can take the yellowing out.
> > - Parts do not uniformly yellow, even though all sides are exposed to
> > air. I have monorail track that is partially yellowed, but was
> > presumably completely air exposed.
> > - Parts that get sun exposure yellow faster. This is common lore; can
> > anyone dispute it?
> > - Parts in sealed boxes or in wooden drawers can yellow, apparently
> > faster than parts that get diffuse sunlight.
>
> According to our resident plastics expert at work, both ABS and
> CA (cellulose acetate) polymers will discolour from exposure to
> ultra-violet light. The UV energy directly "attacks" the molecular
> bonds of the polymers. And presumably this damage is cumulative---
> in other words, once there has been exposure, the plastics will
> begin to discolour over time. I would speculate that this is because
> each broken molecular bond releases more energy, further energizing
> the reaction, and so on. Technically it's really a long-term
> decomposition. Polymers in general have a useful life, over which
> their mechanical properties (strength, flexibility, etc.) degrade.
> This is hastened by UV exposure.
>
> Compare the areas of your "white" computer monitor cases that
> are exposed to light to those that aren't as much---you'll see
> it's yellowing, too, if it's old enough.
>
> Also, I was told that ABS should not outgas at atmospheric pressure
> unless heated up to it's softening point. Put it into a vacuum,
> however, and it's a different ballgame. For example even metals can
> outgas in space.
>
> I draw one conclusion from all of this: If your LEGO has ever
> seen light, and unfortunately all of it has (at the factory),
> then it will yellow. The only question is just how long it will
> take.
>
> KDJ
> ______________________________________________________
> Harbinger of LEGO Death #203, Windsor, Ontario, Canada
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