Editing Retrobrite (section)

== Methods ==

These are the approaches in common use. Durations are deliberately '''not''' tabulated on this page: no controlled study of treatment time against UV intensity, temperature and initial discolouration has been published, and the hour figures that circulate are guesses. Work by inspection — check every 20–30 minutes, and stop when the colour matches, not when a timer says so.

=== Peroxide cream and UV ===

The common method. Salon developer cream at 12 % (40 volume) is brushed evenly over the part and left in sunlight or under a UV lamp. The cream is viscous, so it stays where it is put and wastes less than a liquid.<ref name="cosmetics" /> Wrapping the part in cling film keeps the cream from drying; if it dries, the reaction stops. Uneven thickness is the main cause of streaking.

=== Immersion bath ===

The part is fully submerged in liquid peroxide and exposed to UV. This gives the most even result and is the only method that reaches complex mouldings properly, but it needs several litres of peroxide, and a part that traps air will float and band.

=== Sodium percarbonate ===

Oxygen laundry boosters are sodium carbonate and hydrogen peroxide in solid form; dissolved in warm water they give a dilute peroxide solution. Slower and weaker than developer cream, cheap, and easier to handle. The original Retr0bright formula added '''TAED''' (tetraacetylethylenediamine), the activator sold in the same laundry products, to the peroxide.

=== Sunlight alone ===

UV with no peroxide will lighten yellowed ABS over days to weeks. It is the slowest method and the only one that adds no oxidiser to a polymer that is already oxidised. Given the ten-year finding, it deserves more consideration than it usually gets.<ref name="tenyear" />

=== Heat instead of UV ===

Warming the peroxide accelerates the reaction without UV. This trades UV exposure for a warping risk, and ABS softens well below the temperature people assume. Keep well away from the glass transition of the moulding and do not use an oven.

=== Vapour and ozone ===

Peroxide vapour in a sealed chamber, or ozone plus UV, are occasionally used. The vapour method depends on concentrated (30–35 %) peroxide, which is a materially more dangerous chemical than developer cream — see the table above — and is not recommended for hobby use.