Fillers consist of various materials in powder form. They are added to Epoxy-Plus to thicken the epoxy to make it suitable for gluing, stitch & glue structural fillets (see below), cosmetic fillets, filling screw and nail holes, and smoothing surface imperfections. While all fillers "bulk up" the epoxy, only Cab-O-Sil and wood flour act as thickening agents to prevent sagging. Cab-O-Sil is much finer than wood flour, and is typically added to other fillers to attain no-sag and/or smoother characteristics.
The proper mixing procedure is to first thoroughly mix equal amounts of Epoxy-Plus part A and part B together. Then blend in the filler in stages, until the desired consistency is achieved. Since cured epoxy products are very strong, it is best to minimize the sanding effort by smoothing the uncured mixture as well as possible, removing excess material before it cures, and avoiding high spots. It is far easier to fill low spots later than it is to sand off the high spots.
A white, fluffy powder typically added to other fillers to give them no sag or smoother characteristics. Can be used alone with epoxy for gluing or structural fillets. Mix by volume, 1 part of filler with 1 part of mixed epoxy. Makes a smooth mixture. In smaller amounts effectively thickens epoxy for gluing or to reduce sagging on vertical surfaces.
Microscopic reddish brown phenolic spheres for low density, easier to sand fairing compounds. Mix by volume, 2 parts of filler with 1 part of mixed epoxy, adding 1/2 part of Cab-O-Sil to reduce sagging. Makes a smooth mixture that is easy to sand.
MILLED GLASS FIBERS
Ground reinforcing glass fibers that can be added to polyester or epoxy resins, alone or with Cab-O-Sil, to make a very strong, hard mixture. Suitable for filling surface dings and scratches on a fiberglass hull.
When added to epoxy or polyester or epoxy resins produces a surface that can be easily sanded to a feather edge. Inexpensive. Produces a high density compound that is more abrasive resistant than micro-balloons but a little harder to sand.
A tan powder, the consistency of baking flour. Used for stitch & glue structural fillets, general wood repairs and gluing. Inexpensive. Mix by volume, 2 parts of filler with 3 parts of mixed epoxy to make a strong putty. Substitute 1/2 part of Cab-O-Sil to make a smoother mixture.