Fillers are added to resins and gel coats for specific flow characteristics and to extend volume.
Various fillers may be combined for different purposes, such as adding aerosil to microballoons to prevent sagging on vertical surfaces. These fillers may be used with both polyester and epoxy resins
AEROSIL: Aerated silica particles used to thicken resin for glue applications and to prevent sagging on vertical surfaces. It will not reduce tensile strength. It is light and fluffy, but difficult to mix.
ALUMINUM POWDER: Silver additive for abrasion resistance; special order only.
CHOPPED FIBERS: Fiberglass strands ½” long for strengthening a resin mix or add to putty. It makes a coarse mixture that will trap air bubbles if not properly applied.
DECK DUST: A fine acrylic powder used to make a non-skid surface on windsurfers and possibly boat decks. Because of the small particle size, the liquid medium must be a thinned paint or finish resin.
DICAPERL: Hollow filler similar to Q-cel.
GLASS BUBBLES: Lightweight glass microspheres for high build rough faring and filling operations. Easier to control gel time and sand than body filler, but will leave a porous surface that must be primered. In very thick (5”) lay-ups, it disperses heat well to reduce cracking and shrinkage. It is superior in strength and workability to body filler, especially when mixed with epoxy resin systems.
GRAPHITE POWDER: Black carbon powder for a smooth low-friction surface.
MICROBALLOONS (brown plastic microspheres): A lightweight thickener for fairing. It is similar to Q-cel, except it is easier to sand and is more expensive. It will not prevent sagging, and it also reduces tensile strength. Both this and Q-cel can be mixed with aerosil or thiksil to prevent sagging.
MICROCELL: Very light easy sanding fairing material, similar to West System 410 Microlight.
MILLED FIBERS: Finely chopped fiberglass fibers that mix with resin to form a jelly-like paste with maximum strength. It does not lay on smoothly and is difficult to sand.
Q-CEL (quartz microspheres): A low cost lightweight white resin thickener for fairing and filling compounds. It is a little more difficult to sand than microballoons as quartz is a hard material, and it will not prevent resin sagging on vertical surfaces and should not be used for glue as it reduces tensile strength. It is commonly used for patching surfboards because of its light weight.
SILICA SAND: Graded sand (same size particles) for non-skid surface; it may be spread on top of a wet resin or paint surface and the excess swept off after the surface dries; it may also be added to the resin or paint and applied with a paint roller.
TALC: Inexpensive white resin filler used for large casting operations. Due to lack of demand, Fiberglass Hawaii no longer stocks talc, but talcum powder is a reasonable substitute in small quantities.
THIKSIL: Silica particles similar to aerosil except that they are heavier and easier to mix. Both aerosil and thiksil are solid particles that soak up resin and are therefore heavy. It helps reduce sagging on a vertical surface and is easy to mix.
OTHER non-skid materials for boat decks: Crushed walnut shells (brown and sharp-pointed) and beach sand (must be strained, washed, and dried). Fiberglass Hawaii does not currently stock these items.
