Where the colour comes from

The colour of FRP grating comes from pigment in the resin, or from a gelcoat on the surface. Through-colour pigment runs through the whole section, so a cut or a worn area shows much the same colour; gelcoat sits only at the surface and a cut reveals the colour beneath.

Pigment must resist chemicals and weather. Inorganic pigments generally resist UV and heat better than organic ones, and bright yellow and red fade more readily, so weatherability belongs in the colour choice.

Colour is not only decoration. Yellow marks edges and warning zones, dark colours absorb more heat and run hotter, and light colours reflect more and feel cooler underfoot in summer. Choose colour and duty together.

On one project the grating colour also has to sit with handrails, kick plates and structural steel. Leave the decision too late and the only option is a compromise in a less visible area, which shows in the finished look.

Pigment versus gelcoat

Pigment sits inside the resin, costs less, repairs easily and gives even colour through the part; gelcoat sits on the surface, is denser, resists weather and chemicals better, but a repair shows a clear colour difference.

Load-bearing parts should not rely on gelcoat to hide defects. Gelcoat must be even in thickness: too thick and it cracks, too thin and it protects nothing, so thickness is controlled by the production process.

Where colour depth must be consistent, ask whether the part is through-coloured or gelcoated. The two behave quite differently at cuts, wear and repairs, and the quotation should say which is offered.

Gelcoat usually gives a more even colour than pigment but is harder to repair. Where local repair matters, through-colour is more practical; where surface weather resistance and easy cleaning matter, gelcoat has the advantage.

UV and fading

Ultraviolet light degrades the resin surface in a familiar sequence: loss of gloss first, then chalking, then a colour shift. Darker colours run hotter at the surface and generally age faster.

UV absorbers, a surface veil or a gelcoat all slow fading. Some fading after years outdoors is normal, and outdoor grating should not be held to an indoor colour standard.

Fading alone does not mean lost strength. What matters is the depth of chalking, exposed fibre and cracks; grating that has changed colour but kept a sound surface can usually stay in service.

Judge fading after cleaning. Dust and surface exudate make the colour look pale, and a comparison after washing with neutral detergent is more reliable.

Why batches differ

Pigment batch, resin batch, cure temperature, mould condition and release agent all affect the final colour. The same formulation made in different seasons can differ slightly.

Exact agreement between batches of one colour is difficult. The industry usually controls it with a colour meter on a colour-difference value, with the tolerance agreed between buyer and maker and written into the order rather than left verbal.

Large installations should buy from one batch where possible, or at least keep one visual area to one batch. When deliveries arrive in stages, compare them with the sample before deciding which area each goes to. Colour and specification are linked in the colour and specification data

How to specify colour

Give a reference system: a RAL number, a Pantone number, or a physical sample agreed by both sides. Writing yellow or grey is not enough, because makers read it differently.

Compare samples in daylight, since colour shifts under different light sources, which is metamerism. Confirm the colour under the lighting of the actual project rather than only in an office.

The order should also state gloss, surface finish (gritted or smooth) and the permitted colour difference. Gritted grating looks lighter than smooth grating of the same colour, a point easily missed when comparing samples.

• State the colour system and the sample number.
• Say whether the colour is through-pigmented or gelcoated.
• Agree the colour tolerance and the test method.
• For large projects, approve a sealed sample before production.

Yellow safety edges

Yellow warning edges mark platform edges, stair mouths, equipment openings and inspection hatches. The colour must be conspicuous and the width follows the project safety requirement, commonly as a proprietary yellow anti-slip strip or edge profile.

Yellow pigment weathers relatively poorly and fades outdoors. A proprietary anti-slip strip can be replaced on its own when worn or faded, which costs less than re-colouring a whole panel.

Safety colour also depends on site lighting and background contrast. Being visible by day does not make it visible at night, so platforms with night work should consider lighting and reflective materials together. The performance of the panel itself is covered under FRP grating benefits

Set the width and position of warning edges by how the platform is actually used. Platforms with forklift traffic, night work or frequent maintenance usually need more than an ordinary walkway.

Fading, staining and cleaning

Surface contamination is often mistaken for colour variation. Rust, oil, algae and dust dull and yellow the surface, and cleaning before judging avoids unnecessary replacement.

Clean with a neutral detergent and a soft brush, avoiding strong acids and alkalis and close high-pressure washing. Strong alkali attacks the resin surface, and high pressure can strip the grit or the gelcoat.

Rusty water from steel parts leaves stains across the grating; stainless fasteners and prompt edge sealing reduce this. Poorly drained areas that hold water also grow algae and need attention at the same time.

Set cleaning frequency by how fast dirt appears rather than by a fixed rule. Dusty plants need more frequent washing and clean areas less; what matters is rinsing residue away so the cleaner does not become the contaminant.

Reordering and batch matching

When reordering, give the original batch number, colour code, resin type and a physical sample. Without records only an approximate standard colour is possible, and the difference shows when new panels sit beside old ones.

New panels rarely match old ones exactly, especially after several years of service. Put the new panels in a less prominent area, or replace a whole zone together, to avoid a patchwork look.

Keep the colour sample and batch record at handover for the maintenance team. Buying against the record is easier than matching colour afresh each time. Colour expectations by industry are covered under industry applications

When a project takes several deliveries, lay a small trial area first and confirm the difference is acceptable before covering a large area. Keep a panel from the trial as a reference for later comparison.