Yes, you can indeed have another go at reticulating a piece if you
didn't get all the areas the first time, or if you hope to get a
little more definition in the wrinkles.
Happily, you do NOT have to go through the heat/pickle stuff several
more times. With reticulation silver, the key physical feature is
not the fine silver layer at all: it is the oxide layer underneath
it, the unmelting cuprous and cupric oxides. It is these that form
the temperature resistant envelope within which the molten or
semi-molten metal moves; it is the firescale that resists that
movement. Yes, you will get a fine silver layer after the
heat/pickle cycle, but research done by myself, Andrew Nyce [a
metallurgist turned passionate jeweler] and Stewart Grice [Hoover &
Strong's metallurgist] definitely showed that it is the oxide layer
that is more important. In fact, you can get lovely reticulation
without pickling at all.
In Tim McCreight's wonderful Complete Metalsmith he suggests
conditioning reticulation silver by placing it in a kiln at 1200
degrees F. for 8 to 12 minutes. You take it out, let it cool, and
reticulate it. Metal treated this way reticulates beautifully and
easily. This works so well that Hoover and Strong are probably going
to produce and sell pre-conditioned, ready-to-reticulate 80/20
That said, there are a couple of other factors that will definitely
influence the quality of the reticulation you get. The first factor
is fuel gas. We have found that propane, either with air or oxygen,
seems to give us the best results with the fewest disappointments
[i.e. places where the oxide layer breaks and the molten center
boils outward -- looks like little black bumps on the piece].
Personal torch skill is also very important -- a good, practiced
hand can get terrific results and amazing control when an
inexperienced person won't do as well on the identically prepared
metal, with the same torch, and the same substrate. You really do
develop a "feel" for the intensity of the flame, the rate of
heating, and the way you move the flame once reticulation begins.
It's great fun when you can actually sign your name across a piece
of silver in wrinkles.
I use an acetylene torch because that's what I have right now, and
with practice I do get extremely nice results; my friend Andrew Nyce
gets more dramatic results more readily using propane, and our
students and colleagues have found this to be largely the case. So
if you just have acetylene, don't despair, you'll do fine after a
few tries. But propane may well make it easier.
The gauge of the metal will influence the nature of the reticules
somewhat. I like working with 22; my friend Andrew does delicious
things with 18; much thicker than that, and the results become
muted. Thinner than 24g and you risk having the metal pull itself
apart during the formation of wrinkles.
The next factors involve bench set up. In particular, you have to be
able to work with NO drafts across the area. This may mean
temporarily altering the way your ventilation system works for the
few minutes that you are reticulating.
The substrate you are working on is another important detail. I have
found that magnesia wool or ceramic wool [available from sellers of
kiln supplies and refractory materials] work extremely well.
Solderite boards, honeycomb ceramic boards, charcoal, pumice,
carborundom, and magnesia blocks are all very inferior to the
refractory wools. Not only can the wool be cut to the right size,
and used repeatedly, it can also be packed, crammed, and shaped to
support reticulation silver that has been made into three
dimensional forms such as seamless tubing, boxes, and bracelets --
these are reticulated AFTER being shaped. [If you want to see an
example, look in the Rio Grande tool catalog in the forming tool
section where the Bonny Doon presses are, and you will see a box of
reticulation silver with a moldavite finial and black pearl feet.
The reticulation was done after forming, and it was that sequence
which created the dramatically curved and concentric reticules.]
There are other wonderful things you can do to manipulate the
reticules once you have gotten comfortable with the basic process.
Heat sinks, keum boo [both before and after reticulation], thermal
isolation, varied geometry of sheet and hollow forms, using gravity
to affect wrinkle shape ["snakeskin" reticules], and yes, you
certainly can do lots of forming, and fabrication, including
soldering, prior to reticulation.
There is a lot of misout there about just what you can
do either before or after, so I will mention this: in Finland [and
also perhaps Denmark], when my friend Wendy Yothers [now a
conservator of holloware for Tiffany & Co] did her training in the
guild schools, the students got 80/20 sheet to do their assignments.
If they did the work correctly, then they were given sterling to do
the thing over in its final form. So clearly they were working out
the prototype in a really bitchy [pardon me] alloy -- it is stiff,
firescales almost instantly, is horrible to hammer, and the moment
you heat it incorrectly it betrays your error by -- yes! --
wrinkling. In fact, when Heikki Seppa was first exploring
reticulation at Cranbrook years ago, he was playing with it as a
known phenomenon from his training at home in Finland -- except
there it was a sign of failure and a thing to avoid. He thought it
was nifty and worth trying to control and develop for its own sake.
If you are interested in forming reticulation silver into hollow
shapes prior to reticulation, I highly recommend the use of a
hydraulic press and tooling. The press doesn't take cheek from any
uppity alloy, and it sure does do the job faster than you can with a
hammer, and with fewer annealings. When you do anneal, be sure to
use a blob of paste solder on the piece to tell you when you have
reached 1200 F so you can quench -- don't ever overheat reticulation
alloy if you want to move it easily afterwards, because it can
become quite brittle [it's that firescale layer acting up]. I
suspect that folks who have been frustrated in forming it may have
inadvertently overheated it while annealing, and since it's stiffer
than sterling it needs annealing frequently, so this could add up to
a really unhappy experience for both the metal and the metalsmith.
I don't have a good answer to your question about coin silver. I
believe that term has specific alloy connotations, but I have no
idea if these are consistent around the world and I don't know where
you are -- someone else will have to help you there. You can also
look in a reference like Utracht's book, or Tim McCreight, or
Brepohl. Coins are so tiny, though, and you really need a bit of
space for the reticules to grow and breed -- you may find it very
frustrating to work so small.
I realize that I have just dumped a whole load out into the
reticulation discussion and I do apologize. I will try to get things
put into a more organized form and send it to Our Fearless Leader to
tuck into the reference archives. I will rope Andrew and Stewart
into the project, too, just to be thorough. Maybe Stewart can give
us some of the micrographs of prepared alloy and reticulated
alloy...they are really nifty, just like a slice across a sandwich
only more informative.
Terrie, please do not ever be afraid to ask a question on Orchid.
You are almost never the only person with that question, so you are
doing a great service to them as well as yourself when you ask. And
save your cajones for the other difficulties you may have ahead of
(who is really just a person with lots of hammers in the basement)