Retrobrite

Retrobrite (retrobright) is a chemical mixture used to remove yellowing from acrylonitrile butadiene styrene (ABS) plastic computer and electronics case. The original meaning has been expanded, so now "retrobrite" often refers to indicate any H2O2 based process used to remove yellowing from ABS plastics.

Yellowing in ABS plastic occurs when it is exposed to UV light, among other factors, which causes photo-oxidation of polymers that breaks polymer chains and causes the plastic to yellow and become brittle.

Composition
Retrobright consists of hydrogen peroxide, a small amount of the "active oxygen" laundry booster TAED as a catalyst, and a source of UV Light (Usually either from the sun, or via an artificial source such as a UV Lamp). Some will include a gelling agent (Xantham Gum, Arrowroot, etc) to thicken the mixture to reduce the total amount of solution required.

Active Agent
This is the component that will be doing the majority of the work.
 * Hydrogen Peroxide H2O2 (12% is the recommended percentage. 40 Volume Hair Developer is 12%)
 * If buying hydrogen peroxide from a pharmacy or hairdressers, check to make sure it has no other additives. All you want is diluted hydrogen peroxide (typically 3% to 12%). Additives may lead to unpredictable results.

Catalyst
Using a catalyst is optional, but in theory will increase the bleaching properties of the H2O2
 * Tetraacetylethylenediamine (TAED) - "active oxygen" laundry booster (OxyClean, Oximagic, etc)
 * TAED and hydrogen peroxide react to form peroxyacetic acid, a more efficient bleaching agent.

UV Light
UV Light is REQUIRED for the entire process to work.
 * The Sun
 * UV Lamp

Gelling Agents
 Gelling agents are used to thicken the solution, they are NOT required, but do allow you to use less ingredients.
 * Arrowroot
 * Xantham Gum

Premade Solutions
NOTE: These premade solutions still require the use of a UV Lamp or other UV Light source to bleach the yellowing of plastics

Hair Developer
Hydrogen Peroxide(H2O2)-based hair bleaching creams available at beauty supply stores can also be used as a ready-made mix and are labeled by Volume.

40 Volume contains the 12% peroxide solution recommended for lightening yellowed plastics.
 * 40 Volume Hair Developer (Creme/Gel or Liquid)

DIY Recipes
'''A lot of these recipes are out-dated and are archived here for reference. While they are good starting points, it is recommended that you do your research and find a recipe that is cost-effective and efficient for your uses.'''

Items Needed

 * 1 pint (500ml) - Hydrogen Peroxide, 10 to 15% strength (40 vol) (available from hairdressers' supplies, e.g. the 'Sally Beauty' franchise in the UK)
 * 2 heaped tablespoonfuls - Xanthan Gum (available from health food shops or online)
 * 1 level teaspoonful - Glycerine (available from pharmacies)
 * 1/4 teaspoonful - "Oxy" laundry booster

Steps

 * Add the Hydrogen Peroxide and Xanthan Gum to the blender or liquidiser.
 * Mix on high speed for 5 seconds.
 * Add the Glycerine and mix for a further 5 seconds.
 * Let the mixture rest for a minute then mix again for 5 seconds.
 * A smooth, non-drip gel should have formed.
 * This gel can be put into a dark colored jar or tub (e.g. a coffee jar covered in tape) and stored, as long as you DON'T add the "Oxy" until you are ready to use it.

Lorne's Variant Recipe
Lorne at Vintage Computer Forums prefers to use stronger Hydrogen Peroxide and his variant recipe is below.

Items Needed

 * 1/2 pint (200ml) - Hydrogen Peroxide, 30% strength
 * 2 level teaspoons - Xanthan Gum
 * 1 level teaspoon - Glycerine
 * 1/4 teaspoonful - Oxy laundry booster
 * 1 teaspoonful - hot (not boiling) water

Steps

 * In a very small ceramic or plastic bowl/dish, dissolve the Oxy in the hot water.
 * Lorne found that the Oxy doesn't want to dissolve in the paste/gel very well - this premixture of the Oxy fixed that problem.
 * While the Oxy is dissolving, mix the Hydrogen Peroxide and Xanthan gum in the blender for five seconds.
 * Add Glycerine to that mixture and blend for another five seconds.
 * Let mixture sit for five minutes.
 * Blend for another five seconds.
 * Just before you apply the gel, thoroughly stir in by hand, the dissolved Oxy/water mix.

Tezza's Arrowroot Variant Recipe
'''Tezza at Vintage Computer Forums came up with a variation of the original recipe, based on another starchy food thickener called Arrowroot. Also, Tezza's recipe doesn't use glycerine. Trials have found the arrowroot-based paste dries out more quickly than the Xanthan gum/glycerine mixture in the recipes above and requires more frequent re-application. However, Arrowroot tends to be easier to find than Xanthan gum and is a workable alternative where this is the case.

The addition of glycerine may help to slow the drying processes but Tezza has not tried this at the time of writing.'''

Items Needed

 * 1/2 pint (200 ml) - Hydrogen Peroxide, 6% strength (available from most Pharmacies as a hair bleach or antiseptic)
 * 2 heaped tablespoonfuls - "White Crest" Arrowroot
 * 1/5 teaspoonful - "Oxi-Magic" laundry booster (to be added to the gel just before use, like the original recipe. Can probably be replaced by any "oxy-type" laundry activator.)

Procedure
If you use Arrowroot, you will need to heat the mixture. Don't worry, this is safe to do. Tezza suggests warming the mixture up in a microwave oven for about 45 seconds, based on a 750 Watt microwave oven, you may need to adjust the timings based on the wattage of your microwave. He strongly suggests that you do this in 15 second bursts and check the consistency after each burst. It's ready when is appears as a gel. Sprinkle in the Oxi-magic and stir vigorously with a spoon. This will also help thin the mixture so it can be brushed on.

Foaming when adding Oxi-Magic is related to how hot the mixture is and the concentration of peroxide. Usually the foaming is mild but if ithe mixture is hot and higher concentrations of peroxide have been used, the reaction can be vigorous. It would pay to let it cool first.

Simon Lock's Vapor Method Recipe
Simon Lock shared a different way to retrobrite commonly called the "vapor method". Instead of submerging objects in a hydrogen peroxide solution, you place a much smaller quantity of the solution in the bottom of a container, then place the object(s) to retrobrite onto a stand inside the container, sealed and exposed to UV light.

Items Needed

 * 1) Hydrogen Peroxide, 12%
 * 2) A stand for the item
 * 3) Large enough container for the item on the stand, along with a lid

Procedure
Pour the hydrogen peroxide into the container, enough to cover the bottom. Place the stand into the container, and place the object to retrobrite onto the stand. Close the lid, and either leave the container out in the sun, or shine a UV light on it.

Note that the object is not submerged in the solution. Instead, the idea is that the peroxide solution will turn to gas, and the vapors will de-yellow the object. The advantages of this method are that you need a lot less hydrogen peroxide, and because the object is not submerged, there is less chance of making the plastics more brittle. Furthermore, you can leave the objects in the container for a lot longer, even multiple days for very stubborn yellowed plastics.