Note: This article was first published on 1st July 2012, but republished several times thereafter for its relevance.
A couple of weeks ago, I received a 20-plus years old Apple Extended Keyboard (AEK). Meticulously, I stripped the keyboard to dust down the PCB within, and to clean the two halves of the casing and the keycaps. Despite getting a super-clean keyboard after all that hard work, I was unsatisfied with what laid before my eyes. What was wrong? Well, with the exception of the keys, the casing of the keyboard (along with the space bar) had yellowed considerably.
Now, this is nothing surprising; we all have plastics that had yellowed with age. Keyboards, mice, printers, gaming consoles - you name it. And no matter how you scrub it, you just can’t get back its original color.
Determined to return my AEK to its former glory (and color), I searched the Internet for a method to ‘de-yellow’ plastics. It turned out that there’s really a way to undo the damage, and the answer has been out there for more than three years. It’s called Retr0Bright. To shorten the chemistry lesson, essentially, the industrious folks behind the Retr0Bright project had discovered that it’s the bromine - often used as flame retardant in plastics - that’s causing the yellowing. And the keys to reverse the process are hydrogen peroxide and ultraviolet (UV) light.
For those adventurous enough, the Retr0Bright wiki has recipes for making the RetroBright gel. Why gel? Because hydrogen peroxide isn’t exactly cheap. For instance, a 50ml bottle of hydrogen peroxide solution (12% strength) costs S$4.90. Imagine the amount you’d need, and how much it’d cost you if you want to de-yellow a large item, like a PC casing.
Then again, if only making the Retr0Bright gel is as easy as pie. If you’ve never heard of hydrogen peroxide before this, it’s unlikely that you’d know what is xanthan gum or glycerine, two other ingredients for making the gel. In addition, getting the mixture exactly right sounds difficult.
While looking for a ready-made peroxide gel, I chanced upon a post in the English Amiga Board, where a member recounted his success with an off-the-shelf cream peroxide product. Many others had also reported success, so I decided to give it a try. In short, yes, it really works.
And here's how you can do it too:
The magic potion that you need is the Jerome Russell Bblonde cream peroxide (40 Vol 12%) that’s originally intended for bleaching hair. A 75ml bottle costs US$1.50 on Amazon, excluding shipping. I reckon a lower strength (6% or 9%) will work just as well, except that it will take you a longer time.
Locally, this looks to be a similar product, but I’ve not tried it - so use it at your own risk.
In a nutshell, all you need to do is to coat the plastic (cleaned and dried, of course) evenly with the cream peroxide. Avoid having the cream coming in contact with your skin or eyes, as it can cause burns. As such, I strongly recommend that you use gloves.
And while you're at the handy man store, pick up a brush and some cling wrap too. The idea is to wrap the coated plastic parts, so that the cream peroxide doesn't dry up too fast. I've more tips towards the end of this article.
UV light plays an important role in the whitening process. So, don't go and lock the treated parts in your cupboard. There's no lack of UV light in sunny Singapore - all I did was to leave them on a table by the window. Alternatively, put the parts under a UV lamp. Remember to check the progress regularly.
This sunning process can take as short as a few hours to as long as a few days, depending on how severe the yellowing is. Once the plastic has regained the color that you wanted, wash the parts thoroughly, and ensure that no residual cream remains.
First and foremost, there's no guarantee that this cream peroxide method will work on all yellowed plastics. So, think it through long and hard before attempting this on your vintage, only-one-left-in-the-world gadget.
If you do try it, remember to never let the cream peroxide dry up, especially under the hot sun. It will cause an ugly bleaching effect that unfortunately isn't reversible (and I've learned this the hard way). This is why I now leave the parts on a table beside the window. I would also check on them and turn them regularly, so that all the sides are exposed to the sunlight. Remember, what's required is the UV light, and not the heat. If it's impractical for you to keep checking on the progress, consider using a UV lamp.
Update: A reader (see comment below) suggested not covering the area being treated with a plastic sheet, as this may result in the streaking effect. Thanks for the tip!
Last but not least, the Retr0Bright wiki has a page that talks about other problems and pitfalls - it's a must read for anyone who is thinking of having a go at restoring their yellowed gadgets.