Hi folks ! I’ve used both Epoxy 220 and 330 (manufacturer: Hughes) for
about twelve years now. I still have some of the original pieces I
made with them, so it’s been a good test of their durability. I used
to do pieces that were heavily dependent on the strength of the
glue,so I tested them pretty thoroughly. Engineer husband helped me
devise tests of shear strength (more or less, sideways application of
force), etc.
I’ll outline their properties.
The 330 is clear, and has stayed clear for as long as I’ve used it.
However, 330 is not as strong as 220. 330 sets up pretty fast. 5-10
minutes working time, full bond in 24-48 hours. 220 is amber colored,
and is stronger than 330. The color means you can only use this where
you won’t see it. 220 sets up slower; you have about a 20 minute
window to assemble your parts. Full bond in 24-48 hours.
For both: Setting time AND strength are GREATLY increased by putting
under a lamp. I use an ordinary swing arm desk lamp with a 100 watt
bulb. I set the piece on something non-flammable (usually an old
cookie sheet), pull the lamp over so the metal shade practically
hides the piece. The bulb is only1-3 inches (2 1/2- 8 cm ) away from
the piece. Curing time is somewhat dependent on room humidity. I test
with a toothpick after about 1/2 hour to an hour.Glue should be rock
hard. As a general rule, if it’s raining, I don’t glue. When I have,
there’s always been something funny about the bond. Set, but not as
strong; spongy-looking. If your pieces will be able to drift off each
other, you must clamp. Keep going back to check! When you leave the
room for a snack, that’s when your pieces will drift and then set
rock-hard. I use office supply black binder clips, which come in many
sizes. Also you can use ordinary wooden spring clothespins, being
careful that the wood doesn’t actually touch any glue. You can also
use scotch tape, which can be peeled away from the cured epoxy, but
it isn’t drift proof. Also, the tape adhesive may melt (be more
careful with your heat lamp), but it’s easy to clean off with
alcohol. I clean up still-wet tools with alcohol (denatured, or any
kind), it’s not the perfect solvent for wet epoxy, but I always have
lots around, and the smell brings back lovely memories of my
scientific illustrator days spent drawing little critters preserved
in it. If your piece has oozing, let it set up part way, then clean
up edges with toothpicks. If it’s smeary use alcohol and a cotton
swab.Then return it to the heat. If your pieces do not set (in 2
hours at the most with heat), your mixing proportions for resin and
hardener were off, and you’ll just have to redo the job. For blending
resin and hardener, I like to use a painter’s palette knife,
trowel-shaped. When fully cured (do wait 48 hours for this), it can
be sanded. “Rings and Things” (sells mostly beads and findings, fimo,
etc., 1-800-366-2156) has their own epoxy formula which is also very
strong, and comes in big bottles at a reasonable price if you have a
lot to glue. It is amber colored. Mixing characteristics are
different ( they give you instructions), and it has a much longer
"open" time to assemble your parts. Abovementioned engineer husband
has brought home many industrial epoxy samples for me to try, but I’m
still happiest with the three described above. (By the way, they can
all be colored if you need to. Lapidaries have told me, but I don’t
know any details) The industrial ones I’ve tried had mostly weird
applications that were irrelevant to me, such as using underwater, or
had an unattractive color. There might be wonderful formulas out
there for special uses. Call Hughes- they make many formulas, not
just “ours”. Good luck. Lin Lahlum