Reversing UV Damage on ABS Plastic

Like so many others, I have been in love with Star Wars since I first saw the movies as a child. I also have a lifelong love for costuming. These loves finally came together in the mid 2000's when I first met some members of the 501st Legion at a convention (for those not in the know, the 501st is an international charity costuming club, specializing in the bad guy characters from a galaxy far far away). In 2009 I joined the ranks of the legion as TK-5246.

I am a Stormtrooper; clean, white, endlessly intimidating, or at least I was. Last year, after not trooping for a few months due to real life keeping me too busy, I pulled my armor from it's bin to discovery a trooper's worst nightmare. My helmet was yellow... How am I supposed to strike fear in the hearts of rebels if my bucket is a color that is synonamous with cowardess. After asking my fellow troopers I discovered that it is a fairly common occurrence, I had three options. I could paint my armor white, attempt to wet sand the top layers of plastic off, or convert it to a sand trooper. None of these were appealing. If you paint your armor once, you can plan on repainting it after every few troops, paint does not adhere well to ABS. Sanding is a lot of pain staking work, with no guarantees that I wouldn't ruin my armor. And if I wanted to be a Sand Trooper I would move to Tattoine.

While on the internet looking for ways of dealing with this cruel twist of fate I discovered Retr0bright. It's an open source formula of ingredients available at your local grocery store developed by vintage computer collectors. It supposedly reverses the process of UV discoloration in ABS. I thought surely there would be hundreds of threads about this on the 501st forums but alas, there were none. Some people mentioned it as a possibility, but it seemed most everyone stuck with the tried and true methods I spoke of earlier. After much debate with myself, I decided I had nothing to lose. I got my materials and tried it. The results are like magic, read on to see how I went about it.

Step 1: What You Will Need

• Rubber gloves
• Paint brush
• Some sort of blender (I used a stick blender)
• Retr0bright (ingredients and formula in the next step)
• UV light source (mine was a CFL reptile light available at most pet stores)
• Miscellaneous measuring spoons and mixing vessels
• Yellowed ABS, in this case a Stormtrooper helmet.

You will not want to skip the rubber gloves. As you can see in the photos, I did not wear them. I ended up bleaching the tips of my fingers before I put some on. High concentration hydrogen peroxide can be nasty stuff and can lead to fairly severe chemical burns.

Step 2: Ingredients for and Making the Retr0bright

• 1- 16 oz bottle of 40 volume hydrogen peroxide (available at hair salon supply stores)
• 2 heaping tablespoons of xantham gum (I got mine at Walmart)
• 1 level teaspoon of glycerin (available at most pharmacies)
• 1/4 teaspoon of Oxyclean or similar laundry booster

Combine the peroxide and xantham gum in a blender, or in my case a ceramic container for use with a stick blender. Mix for 5 seconds on high. Add the glycerin and blend for another 5 seconds. Let this mixture rest for a minute to hydrate the ingredients and then mix again for 5 more seconds. When you are ready to get started add the Oxyclean and blend again. What you are left with is a gel that can be painted on to your surface.

I will say that this makes enough Retr0bright that I could probably have done 5 helmets, so you may want to scale down the recipe.

Step 3: Application

I applied the Retr0bright with a paintbrush, making sure to get a fairly even coat over the entire surface. It should not affect any paint or the vinyl decals, so I painted right over them. I then placed the helmet under my UV light. You can also do this outside on a sunny day. However, you want to be careful that your helmet doesn't get too hot in the sun or it will damage the plastic. I decided to play it safe and use a reptile light, it also gave me the ability to leave my helmet unattended without worrying about something happening to it (like a dog thinking it looks fun to play with).

I left it under the light for about 12 hours, rotating it every couple of hours.

After retrieving my helmet from it's basking spot it needed to be cleaned up. The Retr0bright dries on and can be a little difficult to remove. Scrubbing for a couple seconds, a small area at a time with a little diluted dish soap and a toothbrush then wiping it off with a paper towel did the trick. I probably could have put it in the bath tub or sink and hit it with a sprayer to make things easier, but I have a wireless mic and fans installed in the helmet that I did not want to remove.

Step 4: Science and Retr0bright Info

The yellowing of ABS when exposed to Ultraviolet light is the result of a flame retardant added to the plastic during the manufacturing process. The most common of which is tetrabromobisphenol –A, or TBBP-A. When exposed to UV light the TBBP-A degrades allowing Bromine to become a free radical. The bromine forms a bond with readily available oxygen and causes the yellow color.

By irradiating the ABS with UV light in the presence of more hydrogen atoms, in the form of hydrogen peroxide, we break the bonds between the oxygen and bromine and allow the bromine to bond with the hydrogen, thus reversing the discoloration.

I encourage you to check out the Retr0bright wiki and learn more about the folks who came up with this. It is people like this, who figure these things out and make them available open source that keep maker communities like ours thriving.

Step 5: Results

The results were better that I could have expected. It looks like a new helmet again and I am excited to go back to proudly serving the Emperor.

Thanks everyone for reading, and I hope this helps some of my fellow Troopers keep the galaxy safe.

With unquestioned loyalty,

TK-5246