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Science

Lego Whitening

As I dug through my old Legos as my parents house, it was hard to ignore how yellow the white pieces had become. I have two fairly big sets (Lego Model Team) with lots of white Legos and I was curious how hard it was to make them white again.

First of all, why does white plastic turn yellow over time? The core reason is that bromine is added to the plastic as a fire retardant. Over time, that chemical reacts with the plastic and produces a yellow color. The change can be accelerated by light, especially sunlight. Thankfully, the process can also be reversed… with SCIENCE!

There are many websites out there describing various ways to whiten Legos, but I’ll use the one from the Jangbricks video below. The basic steps are:

  1. Wash with soap and water, brush
  2. Put on eye protection and water proof gloves
  3. Find a plastic container that fits the parts
  4. Completely submerge the parts in 3% hydrogen peroxide
  5. Put in a sunny spot (UV light), 3-4 hours (5 at the most) if it’s mid day direct sunlight
  6. Pop the bubles every hour to make sure the water stays in contact and completely wet
  7. Rinse with water and dry (salad spinner)
  8. Spread the parts out to air dry
  9. Reuse the hydrogen peroxide several times. When it stops bubbling enough, dump it down the drain.

It’s hard to find days with strong sunshine this time of year, but we did get some sun last weekend. I’d say we got about 80% of the way there. I’m debating whether I want to try to find some artificial lights to replace the sunlight piece of the puzzle or just wait until next summer to try again.