403 Microfibers Adhesive Filler is a fine fiber blend. Use it to thicken epoxy blended resin/hardener and create a multi-purpose adhesive. It’s most popular use is for bonding wood. Epoxy thickened with microfibers has good gap-filling qualities but will still do an excellent job of wetting-out/penetrating into wood fibers. You can blend it into any WEST SYSTEM 105 Resin/20X Hardener combination, G/flex Epoxy 650, or G/5 Five-Minute Adhesive. Blended with epoxy, it will cure to an off-white color.
VIDEO: A Guide to Adding Filler to Epoxy
Because epoxy can be thickened with high-density fillers into a non-slumping consistency it can bridge large gaps in wood joints, without loss of strength, thus saving a great deal of time labor otherwise needed to create a strong joint.
Read about how master strip plank boatbuilder Ted Moores used this filler while strip planking the electric launch Sparks. As he explains, The key to a joint that did not fail was to saturate the end grain with mixed un-thickened epoxy until it stayed shiny, followed by a thin coat of epoxy thickened with 403 Microfibers Adhesive Filler.
If your project calls for several batches of the same thickened epoxy, it is best to come up with a recipe. So much epoxy and so much filler per batch. Add measured amounts to the first batch until the viscosity suits your specific need, keeping track of the total amount added. For the remaining batches, all of the filler can be added at once, and the batches will be consistent in viscosity.
The WEST SYSTEM Technical Manual & Product Guide can help you come up with a mix recipe. Check the Filler Guide to find out how much filler to blend into the mixed epoxy to achieve a given consistency. This guide includes recommendations for a variety of viscosities for each of our fillers. Keep in mind that it is just a guide. It’s a good idea to thicken the first batch in stages.