David et al,
Doubt that it is an epoxy, as the epoxies tend to break down over
time, although there are a couple of formulations that would work.
Loctite Corp, makes some special order adhesives that will do the
trick for metal-to-stone bonds; some will withstand boiling in
nitric acid for 30 days!!! BUT....they might not withstand
continuous exposure to ordinary moisture....visit Loctite.com and be
prepared to spend some time going over the technical data.
In a closed area, like you describe for the jade bracelets, a good
two-part epoxy will function well. I use 6-7 different adhesives for
different applications on a daily basis, and frustrating
experiences, including breaking some of these bonds, forced me to do
my research long ago. Like most research though, it is on-going as
the products can change without notice and new products are released
One of the very best off-the-shelf and easily obtainable epoxies is
Devcon 5 Minute Fast Drying Epoxy. (Home Depot, Lowe's, Internet) It
takes 24 hours to obtain 95% of maximum strength, but can be handled
in a few minutes. This is also fine for inlay work, but not a good
choice for bonds that are exposed as water WILL break this bond over
a long period of time.
The bond can be chemically destroyed with methylene chloride (most
paint strippers), acetone, MEK, nitromethane/alkane mixes, etc.
(PLEASE CONSULT MSDS sheets for proper cautions, especially
methylene chloride which IS a powerful carcinogen), but the
closed-off area you describe in those bangles can be a challenge to
release chemically and can take days. As you've discovered, the slow
and judicious application of heat speeds the process and this epoxy
will fail at around 200 degrees. But here's a trick for releasing
most epoxies that we use in faceting:
Place a paper towel on the bottom of a small dishpan and add about
1-1 1/2 inches of water, then the bangle. Place on the stove on
medium haet for 5 minutes, then turn heat to high. Boil the piece
for a few minutes and the stones should release cleanly from most
commercial epoxies; for a closed bond, this may take a while, for an
open bond it is rapid; however, I have seen this fail with the newer
formulation of the Devcon 5 Minute product. But the torch will do
The cyanoacrylates (super Glues) are another family of tenacious
adhesives that can be released with heat, but they require much
higher heat levels than the epoxies. 350 F will usually do the
trick, but the newer formulation of Loctite Professional Grade Super
Glue is very difficult to break with heat. Formerly, a few seconds
of a mini-torch or a minute in a candle flame would release the
bond, but no more. Freezing for a few minutes works on many
adhesives, but not this stuff. The best way I have to found to
remove it is a long soak in acetone or nitromethane. Again, the
closed bond in the bracelets could take a day or more.
Yet another product is the various formulations of UV-curing
adhesives. Quite tenacious, but most will still yield to acetone
over an extended period; some will not, they are there to stay.
Visit Norland Products at Norland.com (I think), and you will see
that they have a product or two that can be cured using your choice
of UV light or low heat! This product is excellent for inlay work
that you wish to last beyond your lifetime. I use it to assemble
doublets for custom faceting consisting of strontium titanate
pavilions and colorless synthetic sapphire caps. Let's say it works
well, but I've never tried to get any apart.
Oh, obviously, before joining, all parts need to be clean.
Isoprpopyl or denatured alcohol is a good choice here. When using
cyanoacrylates, breathing on the pieces will provide a small amount
of moisture that accelerates the bond (!), but is not necessary.
Commercial accelerators in spray form work well, but do reduce bond
strength. Some cyanos will fill gaps, some will not. Some are
water-resistant, some are not.
An extended visit to Loctite's or Devcon's web sites is educational.
I'd like to note that some modern adhesives have a bond that is
stronger than the shear strength of aluminum; in some cases,
stronger than soldering. Some industrial situations where heat
treated steel bolts and nuts are used to attach things have now been
replaced with adhesives, because they are stronger. Many will cringe
at the notion, but the right adhesive is BETTER than prongs in many
situations. There, I said it.
Anyway, I hope that helps some of you.