WEST SYSTEM Epoxy fillers are used to thicken the basic epoxy resin/hardener mixture for specific applications. Each epoxy filler possesses a unique set of physical characteristics, but they can generally be categorized as either Adhesive (high-density) for bonding applications or Fairing (low-density) for sanding and fairing applications. Adding these filling agents to blended epoxy resin and hardener allows you to control the consistency of the epoxy, bridge gaps in joints, create either strong or sandable fillets with epoxy, or alter the cured density of epoxy making it easier to sand smooth.

Filler Selection Guide

Adhesive Fillers ⇐ Highest Density/Highest StrengthFairing Fillers Lowest Density/Easiest Sanding ⇒
Uses & Characteristics with epoxy resin/hardener mixture
404 High-Density
404 High-Density
406 High-Density
403 Microfiber
405 Filleting Blend
407 Low-Density
410 Microlight
Bonding Hardware with Epoxy—Increase load capacity—Maximum strength************
General Bonding (Mayonnaise Consistency) - Join parts with epoxy thickened to create a structural gap filler - strength/gap filling************
Bonding with Fillets (Peanut Butter Consistency) - Increase joint bonding area and create a structural brace between parts - smoothness/ strength**************
Laminating with Epoxy—Bond layers—Gap-filling, strong*************
Fairing with Epoxy—Fills voids—Easily sanded—Gap filling*******

Adhesive Epoxy Fillers

Adhesive fillers are suitable for most epoxy bonding situations especially with high-density materials like hardwoods and metals. Adhesive filler mixtures cure to a strong, hard-to-sand cured epoxy plastic useful in structural applications like general bonding, filleting and hardware bonding.

Fairing filler epoxy mixtures cure to light, easily sandable material that is generally used for cosmetic or surface applications like shaping, filling or fairing. Seal all faired surfaces with epoxy before painting.

Epoxy Additives

Additives are used to give epoxy additional physical properties when used as a coating. Although additives are blended with mixed epoxy in the same two-step process as fillers, they are not designed to thicken the epoxy. See Additives & Pigments. Follow the mixing instructions on the individual additive containers when blending these products into your epoxy resin/hardener mixture.

General use filler selection may be based on the epoxy handling characteristics you prefer. Fillers may also be blended to create epoxy mixtures with intermediate characteristics.

Filler Buying Guide

Quantity of mixed epoxy required for consistency:
Epoxy FillerPackage SizePackage WeightEpoxy filled to Ketchup ConsistencyEpoxy filled to Mayonnaise ConsistencyEpoxy Filled to Peanut Butter Consistency
403 Microfiber
6.0 oz
20.0 oz
20.0 lb
3.8 qt
3.2 gal
48.0 gal
2.5 qt
2.0 gal
32.0 gal
1.0 qt
.9 gal
15.3 gal
404 High-Density
404 High-Density
15.2 oz
43.0 oz
30.0 lb
1.1 qt
3.2 qt
8.5 gal
.8 qt
2.4 qt
6.3 gal
.6 qt
1.8 qt
4.7 gal
405 Filleting Blend
40511.0 oz.8 qt.6 qt .5 qt
406 High-Density
1.7 oz
5.5 oz
10.0 lb
1.3 qt
1.1 gal
27.0 gal
.9 qt
3.0 qt
16.0 gal
.5 qt
1.7 qt
6.0 gal
407 Low-Density
4.0 oz
12.0 oz
14.0 lb
.5 qt
1.7 qt
6.0 gal
.4 qt
1.3 qt
4.8 gal
.3 qt
1.0 qt
3.7 gal
410 Microlight
2.0 oz
5.0 oz
4.0 lb
1.2 qt
3.0 qt
8.9 gal
.9 qt
2.4 qt
7.2 gal
7 qt
1.8 qt
5.6 gal