Epoxy or polyester filler: how to choose in 5 points
Putty is used to fill a hole, chip, or deep scratch before finishing. There are rigid putties (epoxy or polyester) and flexible putties (polyurethane adhesive sealants) which serve different purposes. Here are 5 points to check.
1. Rigid filling or flexible joint
Epoxy and polyester putties harden and can be sanded: they are used to restore a surface. Polyurethane adhesive sealants remain flexible after curing: they are used for watertight seals and installing hardware subject to vibrations, such as the Sikaflex 291i 300 ml or its 70 ml black version. Identify the function first before choosing the category.
Sikaflex 291i 300 ml adhesive sealant
2. The substrate to be repaired
As with resins, polyester putty is used on polyester parts, while epoxy putty also adheres to epoxy, wood, steel, and aluminum. The Speed Filler epoxy filler can be applied to epoxy, polyester, steel, aluminum, and painted surfaces. Do not use polyester putty on an epoxy part.
3. The depth of the repair
For thick repairs (holes, deep chips, sealing), fiber-reinforced putty provides impact resistance, such as reinforced polyester putty. For surfacing and small imperfections, a finishing putty sands more finely, such as polyester finishing putty. For large repairs, work in several layers rather than a single thick application.
Reinforced polyester putty
4. Curing time and use below the waterline
Polyester putty hardens in about twenty minutes at 20°C, which allows for quick sanding and finishing. Epoxy putty requires more time but is more moisture-resistant: the Speed Filler epoxy filler cures in about 6 hours at 23°C and can be used below the waterline. The 1:1 epoxy putty + catalyst is mixed in equal parts.
1:1 Epoxy putty + catalyst
5. Finishing
After sanding, the putty is covered with paint, varnish, or gelcoat. On a polyester hull, transparent topcoat tinted with pigment for topcoat allows you to match the color of the hull. For flexible joints, choose the color of the adhesive sealant: Sikaflex 291i is available in white and black.
Talamex transparent topcoat
Find all products in our resins and putties collection.