taken from west marine directly
? Adding a small amount of one of these solvents has a significant effect on the
viscosity of the epoxy. For example, adding 5% lacquer thinner makes about
a 60% reduction in viscosity (Figure 4).
? Adding 5% lacquer thinner to epoxy reduces the epoxy?s compressive
strength by 35%?a big hit in the mechanical properties of WEST SYSTEM
epoxy (Figure 5). The addition of more than 5% solvent results in an
excessively flexible cured material. Thinning epoxy with solvent causes
enough loss of strength that we (and most other reputable epoxy formulators)
cannot recommend using it as a structural adhesive.
? Adding a volatile solvent extends the pot life and cure time of epoxy and
jeopardizes the reliability and predictability of cure. Additionally, with slow rate
of cure, it takes longer before work can be sanded.
? Adding volatile solvent may cause shrinkage of the cured epoxy. Applying
thinned epoxy in large, confined areas (like consolidating a large pocket of
rotted wood) is likely to trap some of the solvent. In thick applications, the
epoxy cures very quickly and not all of the solvent has time to evaporate
before the epoxy hardens. Over time, the solvent works its way out and as
this happens, the cured epoxy shrinks and in many instances cracks.
Shrinkage also causes print through. You may have a surface sanded smooth
only to have the resin shrink. This shrinkage often reveals the texture of the
substrate. Shrinkage can continue to be a problem until all the trapped
solvent works its way out of the cured epoxy.
? Adding solvents, especially acetone, alters the color of the cured epoxy.
While the effects are not immediate, adding acetone to epoxy causes the
color to change from slightly amber to very dark amber.
? Adding solvent results in a temporary reduction in viscosity. Volatile solvents
evaporate quickly as they are agitated during brushing or rolling, causing the
viscosity to continually change as time passes.
? Adding solvent to epoxy may damage the substrate. Many materials
(Styrofoam? for example) are not attacked by epoxy but may be attacked by
the solvent used to thin the epoxy. Be certain to test the substrate with the
solvent before using it to thin the epoxy.
? Adding volatile solvent to WEST SYSTEM epoxy has some adverse health
and safety effects. WEST SYSTEM epoxy components are nonflammable but
the chance of fire or explosion goes up in proportion to the amount of solvent
you add. Also, the vapors of many volatile solvents are hazardous to your
health and proper ventilation is mandatory to prevent inhaling harmful
quantities of them.
? Adding volatile solvent to epoxy which is then applied as a coating may cause
problems with various regulatory agencies. If your business is inspected for
air quality, adding volatile solvents to WEST SYSTEM epoxy may make your
business non-compliant.
? Adding solvent to epoxy to enhance fiberglass wet-out will result in more
?drain out? of the resin on a vertical surface. The fabric will wet-out quickly but
it may become resin starved when too much epoxy runs out of the fabric
