.                   ....

Using Hydrogen Peroxide to
.   'Get the Yellow Out'

.                from George Rentovich, the guys on the English Amiga
.                                    Board, and Rubywand
 

     Years of exposure to sunlight and other UV can result in yellowing or
even browning of Apple II cases. One solution is to pick a color and paint the
case via a few light coats of a spray paint. If you want to restore the
original color, you can get a good match using Apple II pictures available on
the net.

     A recently discovered alternative to painting is bleaching out the
discoloration using hydrogen peroxide (H2O2). According to claims, the process
described here does not damage painted labels, metal inserts, etc. except as
they may be attached by a water soluable adhesive.
 

Note: Most of the info here comes from the English Amiga Board at
http://eab.abime.net/showthread.php?t=37808 .
 

What You Need

- Hydrogen peroxide (H2O2)- water added as necessary to get desired
  concentration

- An 'Oxy' cleaner such as Oxi Clean Versatile Stain Remover or Vanish Oxy
  Action or pure TAED (Tetra Acetyl Ethylene Diamine)-- don't need much

- UV 'Blacklight' bulb (60 watts or so) in a lamp (indoors) or sunlight
  Note: Do not use other UV sources, such as germicidal lights.

- Plastic or glass container (possibly with a transparent cover)

- Bostik Blu-Tack or similar reusable adhesive to help hold small parts in
  position

- Water close by, such as in a large bowl, for washup and washing off cleaned
  parts

- Rubber gloves

- Full protection goggles. You only get one pair of eyes!

- Tongs may be helpful for retrieving smaller parts
 

WARNING: Do Not even think about mixing in chlorine bleach with the H2O2!
The result could be to release chlorine gas.
 

Hydrogen Peroxide Mixture

     Hydrogen peroxide(H2O2) comes in two well-known forms: stable and
unstable (rocket fuel) determined mainly by concentration. The highest
concentration which is commonly available and which is allowed for postal
shipping is 35%. H2O2 in useful strengths is available in various forms and
concentrations from several sources including chemical sellers, cleaner
makers, and hair product sellers.

     Sometimes H2O2 concentration is expressed in "volume". A peroxide product
for hair bleaching may be labeled "40 Volume". To get the % concentration, you
divide by 3.3. 40 Volume = about 12% H2O2.

     H2O2 specified as "not less than 20% nor more than 40%" is available in a
gallon size as a cleaning product called "Urine Rescue" by Prochem for about
$15/gallon. You can obtain 12% H2O2 (such as "Super Star 40 Volume Clear
Peroxide Gallon" for $7.77/gallon) from various hair salon sellers.

     The higher the strength, the speedier the whitening. However, at 35% you
have a more hazardous solution (e.g. in terms of skin/eye splashes) and will
need to monitor the process more closely to avoid etching of the plastic.

     Another factor is that the H2O2 you use will probably not retain its
whitening properties for more than a few days. If you use lower concentrations
you can stretch out your H2O2 supply over more cleaning sessions. A good
balance of speediness, hazards, and cost is around 20% H2O2. 12% is fine, too,
but, slower. Whatever your concentration, you will need enough to keep the item
being whitened wet during the process.

     Plain H2O2 is not particularly speedy as a whitener below roughly 100
degrees F. So, to activate the H2O2 a small amount of TAED (Tetra Acetyl
Ethylene Diamine) is added at the start of the process. One popular cleaning
product containing TAED is Oxi Clean. About 1/4 teaspoon per gallon
of H2O2 solution is enough.
 

Container

     This process requires UV light on the surfaces you wish to whiten. (This
can come from the sun or a blacklight bulb.) Whatever container you use needs
to keep the plastic part(s) in the solution and to allow light to reach the surfaces.
Since the process does generate some heat it is best to avoid using
exceptionally flimsy plastic containers.

     Some smaller parts may tend to float due to build up of gasses in gaps
and recesses. A reusable adhesive gum, like Blu-Tack, can hold them in position
in the tank so that keytops, etc. stay emersed in the solution and get light.

     The container, tank, etc. needs to be out of the reach of small children
and pets. Be sure to let older children and anyone else who may be able to
reach the container know that the stuff inside is not plain water and is
hazardous. Place warning signs/notes on or near the container.

     If outside using sunlight, use a transparent lid or similar covering to
keep out birds and insects.
 

Some Hazards

     The main hazard from H2O2 is probably to eyes. Wear full protection
goggles and have plain water available for flushing eyes or skin in case of
contact with H2O2.

     Another hazard is the oxygen given off during the process. At higher
concentrations oxygen can ignite from electrical sparks, candles, etc.. The
place where you do the process should be well ventilated.

     The UV light to be used for indoor work is 'blacklight' UV. It is sometimes
used to highlight posters in darkened rooms. (Other UV sources, such as various
germicidal lights, can be more hazardous to vision.)  It is best to avoid long
exposures. Do not stare at the lighted process for extended periods.
 

Process

1- Thorougly clean the item(s) to be whitened with soap and water.

2- Set the container for the cleaning process in a safe area out of reach of
   small children and pets.

3- Place the item(s) in the container. If KB keys or similar small items are to
   be cleaned, you may want to stick them in place with Blu-Tack, etc..

4- Put on goggles and gloves.

5- Pour in the H2O2. Add water to get desired concentration. Do not fill to
   brim. Allow some room for foaming activity.

6- Add 1/4 teaspoon of an 'Oxy' cleaner or pure TAED per gallon of
   H2O2 solution. (Expect some foaming action.)

7- If indoors, turn On your blacklight(s). Check that surfaces to be whitened
   are getting light.

8- Every hour or so check the progress of the whitening. Time required depends
   upon many variables. It may be a few hours, several hours, or a few days.

9- When whitness is satisfactory, remove the part(s). Wash or submerge in
   plain water and dry.
 

The Gel Option!

     In order to simplify whitening larger items such as cases, the EAB guys
have developed an H2O2 gel which can be brushed on.

     Here's a quickie summary from a posting by Merlin ...
 

Ingredients

 1 pint Hydrogen Peroxide, at least 20% strength
 1 teaspoonful xanthan gum (health food shops or Ebay)
 1/2 teaspoonful 'Vanish Oxy Action Plus' (any 'Oxy' laundry booster will do)
 1 teaspoonful glycerine
 

Equipment

 Gloves and Goggles (Safety First!)
 1 UV blacklight lamp
 Liquidiser or hand blender
 

Procedure

     Chuck all ingredients except the Oxy into a container and mix until a
smooth thick gel is formed.

     Just before you use it, add the Oxy in by stirring and then brush the
mix onto the item to be treated. Stick it under the UV lamp.

     Check regularly until the yellowing has gone..

ref: http://eab.abime.net/showpost.php?p=467655&postcount=294

Take care!