Silica Fillers
Fiber filler
Wood flour
Graphite powder


Fillers are additives mixed with activated epoxy resin to increase bulk, prevent sagging and to change color. Many things can be used as fillers including saw dust and sand. However, saw dust is not generally uniform in size and sand is heavy, both may well contain undesirable elements other than wood or sand. An industry has developed to provide predictable fillers for everything from ice cream to concrete. GLEN-L has taken advantage of this technology and selected several fillers to improve certain characteristics of the resin to increase its versatility.


SILICA is a "thixotropic agent" added to prevent sagging of thickened POXY-SHIELD® resin, especially on vertical and overhead surfaces. Silica and activated epoxy resin is also used to form high-density filleting materials and putties. Silica is used in combination with our other fillers to give the mix a smoother or creamier consistency. GLEN-L offers two types of silica, #1 and #2. Silica #1 is the premium filler. Silica #2 has most of the characteristics of #1 except that it does not spread as well and has less volume per pound but is more easily sanded. Order on the basis of 1/2 lb. per gallon of resin for a creamy consistency (as for a fairing compound), or 1 1/2 lb. per gallon of resin for filling and filleting purposes.


MICROSPHERES are microscopic, hollow, gas-filled spheres in a fine powder form of low density and weight. They extend the resin and increase the viscosity, forming what is called a "syntactic foam" in higher volumes, ideal for fairing/filler compounds, putties, for making low-density fillets, and for use as a laminating adhesive where gap filling qualities are desirable. The main advantage of Microspheres is that it makes the cured resin mixture easier to sand; the more Microspheres added, the easier sanding becomes. However, if too much Microspheres is added, the mix becomes unworkable. For laminating work, the activated resin/Microspheres mixture is usually still quite fluid. Order on the basis of 1 lb. per gallon of resin for a creamy consistency, or 2 lbs. per gallon for a more paste-like consistency.


FIBER is added to activated POXY-SHIELD® as a thickening agent for use as a structural adhesive or glue. lt provides excellent gap filling qualities while retaining necessary wetting and penetration to prevent glue-starved joints, especially in end or edge-grain situations. The amount added varies depending on the gap filling properties desired; if the joint is a close fit, only a small amount (5% to 15% by volume of resin) is required. Larger percentages are necessary for filling larger gaps. Order on the basis of 1 to 1 1/4 lb. per each gallon of resin as an approximation when POXY-SHIELD® is to be used as a glue. Mix with small amounts of our #1 Silica filler to form a smoother, non-sagging consistency.


WOOD FLOUR is used as a thickening agent in fillets, fairing putties, or glues when the surface is to be finished natural. Not as creamy or easy to work as #1 Silica, but the only one of our fillers that has a wood color. You can add one of our other fillers to adjust color and change the characteristics. Order on the basis of approx. 1 lb. per gallon for a creamy consistency or approximately 2 lbs. for filleting purposes.


GRAPHITE POWDER is used as a coloring agent and to produce low friction exterior surfaces. Graphite Powder is a fine black powder that can be mixed with activated POXY-SHIELD® to make a low friction coating, commonly used on boat bottoms, rudders and centerboards. Not used where the coating will be exposed to strong sunlight. Graphite/POXY-SHIELD® coatings do not provide any anti-fouling qualities but do offer a tougher, more mar resistant surface. Caution: Graphite is a conductor and can cause electrolysis problems in salt or brackish water. Add up to 10% by volume.

A NOTE ABOUT TALC: Talc is another material that can serve as a filler. We have done testing with talc in a wide range of bonding situations and have found that it works similarly to Silica or Microspheres, with similar initial bond strength capabilities. However, there is a question about the tendency of talc to absorb moisture, and in some conditions, this may result in questionable results. Hence, we feel that the conservative practice is to avoid its use.

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