Yesterday I used the retr0bright plastic restoration technique to remove some yellowing from an old computer keyboard. After spending hours researching the various techniques on how this can be done, I have put together this brief tutorial guide on how to restore your own yellowed computer plastics.
The retr0bright process involves using chemicals to reverse the yellowing that is often seen on vintage computer equipment that has been exposed to sunlight over the years. The plastics used in computers from the eighties and nineties were usually treated with a bromine based fire retardant. Over time this compound degrades and discolours plastics (such as beige cases and keyboards).
Two of the most popular restoration methods are submersion in liquid hydrogen peroxide and application of thickened hydrogen peroxide paste. With either method, the treated plastics are exposed to ultraviolet light (usually outside in bright sunlight) for several hours before being washed clean with water. I think the liquid hydrogen peroxide method is superior as whilst the paste method can be more economical, it carries a risk of ruining the plastic with uneven lightening. It’s also less messy and easier to do. Below I demonstrate the liquid method on some 20-year-old Commodore Amiga key caps.
Safety Warning: Concentrated hydrogen peroxide is a dangerous corrosive chemical. If you follow this tutorial you must use appropriate safety equipment including eye-protection and gloves. Some safety information on hydrogen peroxide can be found here.
You will need to gather up the following items to perform the retr0bright process:
- 2+ litres hydrogen peroxide (H2O2) solution (12% concentration but 6% is OK).
- Vanish Oxi-Action fabric stain remover.
- A suitable reaction vessel - ideally transparent. Pyrex glass dishes are perfect.
- Cling-film or saran wrap.
Buying hydrogen peroxide solution on the high street these days is difficult, pharmacies will only sell it in 250ml bottles, so I found the best place to get 12% H2O2 at a sensible price was eBay. To treat a few small plastic pieces or a set of keyboard key caps, about 2-2.5 litres is needed.
The Vanish powder is something many people will have at home already. A chemical in the product called tetraacetylethylenediamine (TAED) acts as a catalyst in the reaction. TAED reacts with the hydrogen peroxide via a process called perhydrolysis, creating peracetic acid. This acid accelerates the removal of the yellow colour via epoxidation of the bromine.
Keep in mind that this reaction is reliant on the ultraviolet light in sunlight, so using a glass container for this is preferable to get maximum exposure. The borosilicate glass in Pyrex kitchenware is ideal as it is basically laboratory grade glass that will be heatproof and chemically inert.
Give your plastic parts a good clean in some warm soapy water and rinse. Then place the parts in your container/bowl and carefully fill with the hydrogen peroxide. In this example I used approximately 2.5 litres of H2O2 to fill the Pyrex dish. Then mix in a small amount of the laundry stain removing powder. The advertised ratio is 5ml of powder per 3.8 litres (a gallon) of H2O2:
It’s important not to be tempted to add extra tetraacetylethylenediamine, as the plastics can get damaged - if the end result is not sufficient, the process can be repeated.
After mixing in the laundry powder you should see some slight fizzing in the mixture and maybe a little foam:
Once the laundry powder has dissolved in to the H2O2 solution, apply cling-film wrap to the container and place it in full sunlight:
Depending the amount of plastic yellowing and local UV levels, the retr0bright mixture should be left in the sun for four to eight hours. Every 1-2 hours agitate the mixture and vent the oxygen gas which will build up under the clingfilm. The solution should fizz slightly when agitated.
If you have any suspicions your H2O2 is expired or no good, submerge a piece of raw potato in some H2O2 - it will gently bubble and fizz if the H2O2 is good.
It should be easy to inspect the plastic parts to determine when to end the retr0bright process. Carefully remove the plastic parts from the mixture and dispose of the solution by rinsing down the drain. Thoroughly rinse the plastics in clean water and allow to dry.
You should now have original looking plastics (or at least substantially reduced yellowing). Note the ‘A’ key which was shown yellowed above is now looking much better:
This ‘after’ shot doesn’t really do the process justice, the white keys are now a uniform and bright tone with no yellowing. Once completed, keep in mind that hydrogen peroxide should be stored in a dark cupboard as it will degrade (and produce flammable gases) when exposed to light. H2O2 generally has an effective shelf-life of about 6 months. Also make sure any glass kitchenware used gets a thorough cleaning preferably in a dishwasher before being used for cooking!
There is a massive amount of information about the retr0bright procedure on numerous vintage computer forums. The original website and information produced by Merlin of AmiBay can be found at retr0bright.com. More recently, the 8-Bit Guy produced a great 20 minute video on the subject titled “Adventures in Retrobrite“ which is well worth a watch and compares some other less well known restoration methods. Good luck!
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