Short answer
Sometimes, by one of three routes: hide the base colour under enough white pigment, remove the colour chemically (bleaching pulp, decolourising glass, purifying monomer), or sort so that only white or clear material goes in. Which is possible depends on the material, how strong the unwanted colour is, and how much cost, energy and loss of other properties are acceptable.
The simplest way to make grey or tinted recyclate look white is to add an opaque white pigment, almost always titanium dioxide, until the base colour no longer shows. The darker and more strongly tinted the base, the more pigment is needed, and even then a heavily loaded white made from grey feedstock tends to look slightly greyer than a white made from a clean base. There is also a downstream cost: RecyClass guidance for white-opaque PET bottles grades titanium dioxide content in bands and treats high loadings as not compatible, and APR notes that titanium dioxide creates haze if opaque PET reaches the clear stream. Hiding colour in one cycle can create a colour problem in the next.
Paper is the material where chemical whitening is routine. Deinked pulp is bleached with peroxide, dithionite or FAS; in one study of mill deinked pulp a two-stage bleach raised brightness by more than nine ISO points, but the pulp made from ordinary grades still finished well below the one made from high grades. Glass can only be decolourised against faint iron tints, by adding selenium and cobalt to neutralise them, and the result is technically a pale grey. Plastics can be whitened chemically only by breaking the polymer down: depolymerisation processes such as glycolysis of PET can separate colourants from the monomer with an extra purification step, restoring a clear base at higher cost and energy than melting.
The most effective route is sorting. Clear PET from bottle-only collection, natural HDPE separated from coloured, flint cullet separated from green and amber, white office paper separated from mixed grades, and textiles sorted by shade all give a light base that needs little or no whitening. The cost moves upstream to collection and sorting, and the achievable volume of white or clear feedstock is limited by what consumers buy and return. For designers this means asking not only whether a recycled white is available, but from which sorted stream it comes.
Many white papers, textiles and some plastics contain fluorescent whitening agents that absorb ultraviolet light and re-emit it as blue, which cancels a yellowish cast and makes the material look whiter in daylight. They do not remove colour; they add blue light, and only where the illumination contains UV. Under UV-free LED lighting, a brightened recycled white can look more yellow than it did in the approval booth. Brightness figures measured with UV included and excluded can also differ, which is one reason a measured target for recycled white should state the UV condition.
| Route | Materials | What it changes | Trade-off |
|---|---|---|---|
| White pigment (TiO2) | Plastics, coatings | Hides base colour | Cost; haze or incompatibility in next cycle |
| Oxidative/reductive bleaching | Paper pulp | Removes lignin colour and dyes | Chemicals; cannot fully close grade gap |
| Decolourisers (Se, Co) | Glass | Neutralises faint iron tint | Greyer glass; no effect on chromium |
| Depolymerise and purify | PET and polyester | Separates colourant from monomer | Energy and cost |
| Sort white/clear feedstock | All | Keeps colour out | Limited supply; sorting cost |
| Optical brighteners | Paper, textiles | Adds blue fluorescence | Only under UV-containing light |
Each statement is labelled by kind — established fact, a standard’s requirement, observed market data, a convention, or Colourwise’s own interpretation or analysis — with the strength of the evidence behind it.
ConventionModerate evidence· Europe
RecyClass guidance for white-opaque PET bottles grades titanium dioxide content in bands, from fully compatible at lower loadings to not compatible above a higher threshold, and also sets a minimum lightness for the outer surface.
Source: RecyClass Design for Recycling Guidelines: White Opaque PET Bottles
FactStrong evidence
After single-stage bleaching with 1.5% peroxide, mill deinked pulp from ordinary recovered grades reached about 62% ISO brightness against about 75.5% for pulp from high grades.
Caveat: One mill's pulps; other furnishes and bleaching sequences differ.
FactStrong evidence
Flint container glass is decolourised with selenium and cobalt, giving a faintly grey glass that appears colourless, rather than by removing iron.
Source: Glass Color Chemistry; Feasibility Study for the Reduction of Colour within the Glass Furnace (GLA0023)
FactModerate evidence
A PET glycolysis process developer states that residual colour components are removed from its reaction mixture so that recycled PET made from the recovered monomer regains virgin-like clarity.
Caveat: Manufacturer description of its own process.
Reviewed 29 September 2026. Colourwise summarises its sources in its own words and does not reproduce standards text or proprietary colour data. Spotted an error? Tell us.