<p>There are several reasons for this:</p>

<ol>
<li><p>There isn't just one formula for the ABS plastic that is used in
LEGO. There are actually quite a few. Depending on the color,
translucency, and function, the mix of materials will vary.</p>

<p>Translucent pieces are quite a bit harder and more rigid than other
Lego bricks. Mini-figure accessories tend to be quite a bit softer
than other pieces (so they don't cause internal damage if/when
swallowed). </p>

<p>If you pull out several types of parts and pay close attention to
the hardness, flexibility, and stiffness, you will notice that not
all LEGO is made the same.  </p></li>
<li><p>Even for similar parts, there is variance in the chemical mixes.
When you get a set, it is highly likely that the parts weren't made
from the same batch of plastic. </p>

<p>Mixing plastics with minor variations can cause changes in the rates
of UV damage and discoloration. It is really hard to get perfectly
matched colors across multiple batches of plastic. </p>

<p>The fact that LEGO colors are so consistent is due to the fact that
they have really high standards for quality control.</p></li>
</ol>

<p>Oh, and if you want to restore your set to that new pristine white color, you can treat it with retrobrite or oxyclean and hydrogen peroxide. There are plenty of articles online if you do a quick search for either.</p>

CC BY-SA 3.0
2018-01-01T08:59:17.380Z
So, what did they do with that hinge to keep it from yellowing, and what disadvantage does it have that keeps them from using it for everything?
Mark
CC BY-SA 3.0
2018-01-01T09:46:28.817Z
+1 for part 2 of your answer - most likely this is btch variation within the parts - different shapes will almost certainly be different batches. Translucent elements are not made from ABS (as it can't be clear) but from a polycarbonate.
Zhaph - Ben Duguid
CC BY-SA 3.0
2018-01-01T04:59:59.927Z
2018-01-01T13:16:12.453Z
2018-01-01T13:16:12.453Z
Roger Hill
<p><a href="https://i.sstatic.net/uBDdw.jpg" rel="noreferrer"><img src="https://i.sstatic.net/uBDdw.jpg" alt="enter image description here"></a></p>

<p>So, here is my LEGO Space Shuttle.  Originally built in 1991, never disassembled (unlike the rest of my sets), so all parts are original and all were exposed to the same amount of sunlight.  </p>

<p>However, the amount of yellowing is highly variable.  The hinge for the manipulator arm (just back of the windshield) is like-new white, and the alignment pin for the arm (just in front of the green brick) isn't much different.  </p>

<p>Two of the wing panels are much whiter than the others, and although it's hard to see, the hinged parts towards the back are two distinct shades of yellow.</p>

<p>What's the reason for this?</p>

CC BY-SA 3.0
2017-12-31T10:24:04.783Z
This is a great question. The Transcon 2 shuttle is notorious for its yellowing.
fabian
<colour><plastics>
Why do LEGO bricks yellow at different rates?
Mark
# Why do LEGO bricks yellow at different rates?

(Asked by: username_0 on 2017-12-30)

[![enter image description here](https://i.sstatic.net/uBDdw.jpg)](https://i.sstatic.net/uBDdw.jpg)

So, here is my LEGO Space Shuttle. Originally built in 1991, never disassembled (unlike the rest of my sets), so all parts are original and all were exposed to the same amount of sunlight.

However, the amount of yellowing is highly variable. The hinge for the manipulator arm (just back of the windshield) is like-new white, and the alignment pin for the arm (just in front of the green brick) isn't much different.

Two of the wing panels are much whiter than the others, and although it's hard to see, the hinged parts towards the back are two distinct shades of yellow.

What's the reason for this?

**Tags:** colour, plastics

> **Comments:**
> **username_1**: This is a great question. The Transcon 2 shuttle is notorious for its yellowing.  

---

## 1 answers

### Answer by username_2 on 2018-01-01. Score: 5

There are several reasons for this:

1. There isn't just one formula for the ABS plastic that is used in
   LEGO. There are actually quite a few. Depending on the color,
   translucency, and function, the mix of materials will vary.

   Translucent pieces are quite a bit harder and more rigid than other
   Lego bricks. Mini-figure accessories tend to be quite a bit softer
   than other pieces (so they don't cause internal damage if/when
   swallowed).

   If you pull out several types of parts and pay close attention to
   the hardness, flexibility, and stiffness, you will notice that not
   all LEGO is made the same.
2. Even for similar parts, there is variance in the chemical mixes.
   When you get a set, it is highly likely that the parts weren't made
   from the same batch of plastic.

   Mixing plastics with minor variations can cause changes in the rates
   of UV damage and discoloration. It is really hard to get perfectly
   matched colors across multiple batches of plastic.

   The fact that LEGO colors are so consistent is due to the fact that
   they have really high standards for quality control.

Oh, and if you want to restore your set to that new pristine white color, you can treat it with retrobrite or oxyclean and hydrogen peroxide. There are plenty of articles online if you do a quick search for either.

> **Comments:**
> **username_0**: So, what did they do with that hinge to keep it from yellowing, and what disadvantage does it have that keeps them from using it for everything?  
> **username_3**: +1 for part 2 of your answer - most likely this is btch variation within the parts - different shapes will almost certainly be different batches. Translucent elements are not made from ABS (as it can't be clear) but from a polycarbonate.  

---

