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Detaching Doublets


#1

Hi everyone, I just made up four quartz-capped ammolite doublets;
three from rough material I sawed and lapped flat with water and 400
grit on a sheet of plate glass, the fourth from a store-bought piece
of rough already slabbed but with saw marks still on, which I
therefore lapped in the same way and at the same time.

As adhesive I used Araldite 2-part epoxy, bought not retail but
directly from a distributor and hence presumably fresh.

After 24 hours curing time for all, I laid them (face down) on the
dop stove to warm them for dopping prior to cutting them into cabs.
In the process of dopping I noticed that all three of the pieces cut
from rough had detached from the quartz cap in large areas; the
fourth piece, from the store-bought slab, was fine and uniformly
glued.

This distresses me. I don’t like having something I make fall apart.
If any lapidarists on the list have first hand experience working
with ammolite, I’d welcome hearing their diagnostic opinion. Is
there, perhaps, a pre-epoxy conditioning treatment? Is there a better
adhesive? An adhesive of choice? What puzzles me is that the
store-bought one stuck, and yet all four were treated equally -
lapped in a water & grit slurry etc etc.

Cheers & thanks
Hans Durstling
Moncton, Canada


#2

Hi Hans, Greetings from the other side of Canada. I suspect you may
have had a contamination problem ,either with oil (from the saw or
fingers) or water prior to bonding. Also heat will destroy an epoxy
glue joint very quickly - try a cold dopping technique instead. I use
Hot Stuff superglue and disolve it with the associated solvent - it
doesn’t seem to attack the epoxy.

Here are some instructions on how they prepare triplets and doublets
at the Spencer Idaho Mine:

http://www.cfmsinc.org/Newsletter/News2001/bulcon01/aa01.htm#6

These are the most complete and detailed instructions I have seen on
making triplets and from personal experience the results are really
good - no separation, no bubbles and the finish product looks good.
The Opticon step is important as it acts as both a sealant and to
eliminate any bubbles in the interface.

Although the instructions are for opal it will work for ammolite
(skip the part about backing it with basanite). The biggest
difference with ammolite is the backing matrix is a bit more porous
and prone to absorbing fluids. I would soak the material for a hour
or two in either alcohol or lacquer thinners to make sure that it is
really clean and all moisture is drawn out. Let it dry for a while
before gluing to allow any residual cleaner to evaporate. Ammolite
can produce some nice results when done as a doublet, I know I enjoy
working with it.

Cheers,
Cameron Speedie
Island Gem and Rock


#3

Methinks that a doublet is probably secured to a dop stick with
something like epoxy so that you do not heat up the stone. removal
would involve a bit of acetone or something that is not allowed to
access the doublet line. Also your doublet may need to cure a while
first. But then, there are probably much wiser ones who will help
on this. Rose Alene McArthur