Colour pastes for unsaturated polyester, vinyl ester and gelcoats have traditionally been made in styrene or in a reactive polyester base. Moving to a styrene-free, non-reactive carrier brings practical benefits on the shop floor.
Cleaner air at the mixing station
A paste with no styrene adds no monomer vapour when tins are opened and colour is weighed. That matters most in small and medium workshops where mixing happens close to laminating.
Stable viscosity in storage
Pastes based on reactive resin can thicken or gel over time, especially in warm stores. A non-reactive ester carrier keeps viscosity steady, so dosing pumps and manual weighing stay accurate from the first to the last kilogram.
Protecting the cure
Because the carrier does not co-cure, the addition level must be controlled. Keep paste additions within the recommended range and check gel time and Barcol hardness when changing colour or dosage. Some pigments, notably certain organic reds and carbon blacks, affect gel time; a quick gel-time test with the actual resin and initiator system avoids surprises.
Good practice
- Stir the paste before use; pigments can settle slightly in long storage
- Pre-mix colour into the resin before adding initiator
- Record paste batch numbers with each laminate for traceability
