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In lugnet.general, Jindrich Kubec wrote:
> Has anybody tried to bleach yellowed parts?
Bleach is great for dirt, but yellowing of ABS is caused by a chemical breakdown
of the plastic molecules, not surface dirt. ABS is not UV-stable, and natural
ABS (which has a milky beige color) will turn brown and brittle/powdery over
time. Some coloring agents will lend a touch of UV-stability to the ABS (black
ABS, which is colored with carbon, is 100% UV-stable), but white doesn't appear
to be one of them. The only way to clean the yellow color off is to scrape away
the surface until you get back down to white plastic, and that's not advisable
if you care about the condition of your bricks.
Now, I know cigarette smoke will cause ABS to yellow, but I don't have any
experience with that. It's possible that you can bleach smoke-yellowing out,
but I'd suggest trying it out on one small brick that you don't particularly
value before subjecting large portions of your collection to the process.
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In lugnet.general, David Laswell wrote:
> In lugnet.general, Jindrich Kubec wrote:
> > Has anybody tried to bleach yellowed parts?
>
> Bleach is great for dirt, but yellowing of ABS is caused by a chemical breakdown
> of the plastic molecules, not surface dirt. ABS is not UV-stable, and natural
> ABS (which has a milky beige color) will turn brown and brittle/powdery over
> time. Some coloring agents will lend a touch of UV-stability to the ABS (black
> ABS, which is colored with carbon, is 100% UV-stable), but white doesn't appear
> to be one of them.
Lego has produced different shades of white and I always wondered if they were
experimenting with additives. Some of the white bricks are just milkier, less
brilliant, out of the box.
One commercial product which absorbs UV (mainly for plastic film?) is Cyasorb
UV-1164, described as "light yellow" "with minimal color contribution". Made me
wonder if there IS an ideal way to protect white plastic without making it less
white.
-Erik
supposed to be doing PDE homework
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In lugnet.general, Erik Olson wrote:
> Lego has produced different shades of white and I always wondered if they
> were experimenting with additives.
It's entirely possible. I've noticed that there are two distinct versions of
the old classic brown when produced in ABS (just the harder plastic used for 2x4
bricks, not the softer plastics), but they only really show up under blacklight.
> Some of the white bricks are just milkier, less brilliant, out of the box.
I just remember that I have some 1x2 flat liftarms that have a slightly grey
tint (and one that clearly has a dark blotch). Do what I'm going to do. Check
'em with blacklight, just to see what they look like. You can get lots of weird
effects with blacklight on LEGO bricks. For instance, red looks almost exactly
the same under 100% blacklight as it does under basic room lighting. Some of
the transparent colors glow, and others don't (this is actually the easiest way
to tell which of the two trans-light blues you have, though I should point out
that the glowing variety doesn't glow anywhere near as brightly as trans-neon
green or trans-neon orange).
> One commercial product which absorbs UV (mainly for plastic film?) is Cyasorb
> UV-1164, described as "light yellow" "with minimal color contribution". Made
> me wonder if there IS an ideal way to protect white plastic without making
> it less white.
Yes. Use a different plastic that's fully UV-stable. If that's your biggest
concern (like, oh, if it's used inside a tanning bed), you pick a plastic that's
completely UV-stable, no matter what color it is. Styrene is UV-stable, if you
don't mind using really cheap plastic that's not going to hold up to much abuse.
Increasing the styrene content of ABS should contribute to UV-stability, but at
the cost of decreasing the heat stability and aging resistance given by
acrylonitrile, and the strength and impact-resistance of butadiene.
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