Short answer
Yes. Pigmented caps melted with natural bottles tint the recyclate, paper labels pulp and release fibres and colour in the wash, and adhesives that do not release keep label fragments stuck to the flake. How much it matters depends on the label's material and density, whether the adhesive releases in hot wash water, and how strongly the closure is pigmented.
Caps are small, but they are often strongly pigmented and made of a polyolefin that is recycled alongside HDPE bottles. WRAP's milk-bottle research in the UK traced the green hue that limited recycled HDPE content mainly to coloured caps, and identified lighter-tinted caps with less pigment in the masterbatch as the most significant quick win. The principle applies widely: a closure colour chosen for brand coding on shelf ends up diluted into the bottle material in the recycler's extruder, where it becomes a faint, unwanted tint.
Paper labels on plastic bottles break down into pulp in a hot wash. The fibres are difficult to filter out of the recycling water and the ink and coatings on them can leach colour. APR describes paper labels on PET as detrimental because the pulp is very hard to filter; WRAP's milk-bottle work found that over-laminated paper labels leached colour and sediment into the wash and recommended switching to polypropylene film labels. A film label of a floating polyolefin can instead be skimmed off whole with its ink.
The adhesive decides whether a label leaves the bottle. A releasing adhesive washes off the PET surface in hot water or caustic and rinses cleanly from the flake; a non-releasing adhesive keeps the label, and its ink, attached to fragments of bottle, so they travel together into the recycled material as specks and tints. European PET guidance rates alkali- or water-releasable adhesives at typical wash temperatures as fully compatible and soluble or non-releasable adhesives as not compatible. Adhesive residue can also yellow or darken when the flake is later dried and melted.
For a designer, the label is the easiest place to put colour on a recyclable pack, because a well-chosen label leaves the bottle and its colour behind. That only holds if the label material floats, the ink is retentive and the adhesive releases. A strongly coloured paper label with permanent adhesive on a natural HDPE bottle is the opposite case: it can put more colour into the recyclate than a lightly tinted bottle would. Checking the label, adhesive and closure specification against current design-for-recycling guidance is therefore part of the colour decision, not a separate compliance step.
Why: Strongly pigmented closures recycled with the bottles.
Fix: Use lighter-tinted closures with less masterbatch, or a closure colour that matches the bottle.
Why: Non-releasing adhesive keeps labels and their ink attached to bottle fragments.
Fix: Specify a wash-releasable adhesive tested with the relevant protocol.
Why: Paper labels pulping and leaching ink and coating in the hot wash.
Fix: Switch to floating polyolefin film labels with retentive inks.
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.
FactModerate evidence· United Kingdom
A green hue in recycled HDPE from milk bottles was traced mainly to pigment in tinted caps and to over-laminated paper labels leaching colour and sediment into the wash; lighter-tinted caps and polypropylene labels were recommended.
ConventionModerate evidence· North America
Recycler guidance describes a releasing adhesive as one that washes off the PET surface and rinses cleanly from the flake, and notes that non-releasing adhesives leave label components as sources of contamination.
Source: APR Design Guide for Plastics Recyclability: PET Rigid
ConventionModerate evidence· Europe
European PET bottle guidance rates alkali- or water-releasable label adhesives as fully compatible, polyolefin labels with density at or below 1 g/cm³ as fully compatible, and metallised labels as not compatible.
Source: RecyClass Design for Recycling Guidelines: Transparent Clear & Light-Blue PET Bottles; Design Guidelines for PET bottles
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.