Pastes and Powders,

Using Resin Pigments, Pastes and Powders

How to Use Pigments, Pastes & Powders in Fibreglass & Resin Projects

Getting the right colour in a fibreglass or resin project is about more than picking a shade you like - it's about using the right type of pigment, in the right amount, for the effect you're after. Whether you're after a solid opaque finish, a glowing after-dark effect, or a neon pop of colour, this guide walks through how to choose and use pigments, pastes and powders correctly, so your project comes out looking exactly as intended.

Why Pigment Choice and Dosage Matter

Every pigment, paste or powder added to resin or gelcoat changes the mix in some way. Add too little and the colour looks weak or uneven; add too much and you risk affecting the resin's mechanical strength, cure time, or clarity. Getting the dosage right is just as important as picking the shade, so it's worth understanding the guidelines for each pigment type before you start mixing.

Standard Pigments: Solid Colour for Resin & Gelcoat

Standard pigments are the go-to choice for opaque, solid-colour finishes in polyester resin and gelcoat. They're the foundation of most coloured GRP work, from boat hulls to decorative mouldings.

Dosage guidelines:

For strong, dark colours in polyester resin, a 6% addition by weight is a good general guide.

Never exceed 10% in polyester resin - adding more won't necessarily deepen the colour further and can compromise the resin's performance.

If you're working with epoxy resin, keep pigment addition to no more than 5% by weight, and stir thoroughly to ensure the colour is evenly dispersed throughout the mix.

Tip: Always stir pigment into resin slowly and thoroughly before adding catalyst or hardener. Uneven mixing is one of the most common causes of blotchy or streaky finishes.

Translucent Pigments: See-Through Colour Effects

If you want colour that still lets light pass through - think stained-glass effects, decorative panels, or artistic resin castings - translucent pigment pastes are the better choice over standard opaque pigments. They're compatible with clear polyester and epoxy resins and come in shades such as blue, red, orange, yellow, magenta and blue-green.

Dosage guidelines:

Translucent pigments behave differently to standard pigments: they become more opaque the more you add, so less is more here.

For best results, aim for around a 1% addition by weight and always stir thoroughly.

If you want a subtler, more transparent tint, start below 1% and build up gradually - you can always add more, but you can't take pigment back out once it's mixed in.

Tip: Test your mix on a small sample first, especially if the finished piece needs to let light through evenly (such as a lamp, sign, or window feature).

Luminescent Pigments: Glow-in-the-Dark Effects

Luminescent (photo-luminescent) pigment powders work on a completely different principle to standard colourants. Rather than simply reflecting light, they absorb light energy from sunlight or artificial lighting and re-emit it as a visible glow once the light source is removed. Supplied as a fine crystal powder, they mix easily into clear casting resins, gelcoats, topcoats and varnishes. Browse the full range of luminescent pigment powders to find the colour and pack size for your project.

Where to use them:

Decorative resin art and jewellery
Signage and way-finding features
Novelty or feature castings where an after-dark glow is the goal

Tip: Luminescent pigments generally need to be mixed into a clear or lightly tinted resin to allow the glow to show through - heavily pigmented or opaque mixes will mask the effect. The more pigment used (within sensible limits), the stronger and longer-lasting the glow will typically be.

Matching Exact Colours with RAL & British Standard References

If your project needs to match a specific brand colour, industry standard, or an existing part, the CFS RAL/BS Colour Swatch Book is the tool for the job. It covers the RAL Classic, BS4800 and BS381C ranges, with over 400 colour swatches in total. Because screen displays and printers can render colour differently from one device to the next, a physical swatch book gives you a true, consistent reference to match pigment against - essential for professional and repair work where an exact colour match matters.

For projects that call specifically for RAL shades, you can also browse pigments direct from the RAL Colour Range.

Quick Reference: Pigment Dosage Guide

Pigment Type	Resin System	Recommended Addition
Standard pigment (dark colours)	Polyester	~6% by weight
Standard pigment (maximum)	Polyester	Do not exceed 10%
Standard pigment	Epoxy	Up to 5% by weight
Translucent pigment paste	Polyester / Epoxy	~1% by weight

Final Tips for Better Colour Results

Always stir thoroughly - pigment that isn't fully dispersed leads to streaking and uneven colour once cured.
Test before you commit - mix a small sample batch first, especially for translucent, luminescent or colour-matched work.
Add pigment before catalyst/hardener - this gives you time to check the colour and consistency before the resin starts to cure.
Don't overdo it - more pigment isn't always better; sticking within the recommended percentages protects the strength and finish of your resin.
Use a swatch book for exact matches - don't rely on screen colours when a precise match is required.

Browse the full range of pigments, pastes and powders, including standard, translucent and luminescent options, at CFS Fibreglass.