03/17/01-- SPECTACVS INTERRVPTVS I'm back to waiting mode, dammit...
The third piece was not a charm, and the electroforming job on the
helmet was so poor that I decided to strip it and try again. There's some
amount of control you have to properly exercise over the process-- current
is supposed to be adjusted at 1/10th an amp per square inch. Calculating
square inches for something like a helmet is difficult and folks like me
are prone to guesstimating. If you do this, you'd better be willing to ride
shotgun over the process-- not turn it on and go to sleep.
I figured that I'd strip the piece by reversing the forming process: use the poorly plated helmet as the anode and a copper strip as the cathode. That's sound science. The big mistake I made was caused by impatience... since I wasn't plating anything, why not bump the current up full blast? That's sound science too. Well, full current generates a lot of heat and apparently the rectifier was not built with adequate ventilation or thermal protection. It died. It's on its way back to the manufacturer for repair or replacement. Who knows how long that will take?
In the meantime, it gave me the motivation to test substitutes for the
rectifier: I'd heard of why you shouldn't use a battery charger, so that
must mean that someone's tried it. The big problem is adjusting the current
flow: chargers are fixed with on/off switches, with no provision for adjustment.
So first, I tried a model train rectifier. These provide you with a means
of controlling the DC output, but they just don't got the juice to do
the job. So I moved on to the battery charger. That worked well for stripping
the helmet lickety split. I insulated the cathode connection wire to prevent
that from disappearing, but eventually it does get to the point where
the conduction to certain areas is cut off, since practically, you can't
control where the copper gets stripped when you want it all gone. Good
enough though, and the manual cleanup job isn't that bad.
As for plating and electroforming-- that's where you need the ability
to adjust current. It helps to have an ammeter, but I only have a VOM
designed for low DC current readings. So I was for all practical purposes,
flying blind. I tried a dimmer switch, but those are rated for 110 volts--
they have too much resistance for 12 volts of electromotive force. You
can use 12 volt lights to limit the current flow, but that's a non-adjustable
limiter. You'd need a hefty rheostat to handle the amperage from a battery
charger and that's why they make adjustable autotransformers, I suppose.
This exercise convinces me that buying a dedicated rectifier is better
for your sanity unless you've got gobs of time to experiment with battery
chargers and homebrew limiters. In fact, one company sells a device which
allows you to turn your battery charger into 4 separate plating stations--
the problem is that it costs well over a thousand bucks! Of course, you
could try dry cells-- those put out 1.5 volts, and adding them in series
gives you some measure of adjustability. However, keeping flush with dry
cells could get kind of expensive too and you'd have that problem of sagging
current as the battery drained.
So I'm back to working on other stuff. The top shield was a small brass
ashtray that had an inappropriate design stamped in the center. I was
able to pound that out and polish it away completely and in the process,
give it the rounded curvature. From this experience, I would have to say
that brass is a far easier metal to work with than mongrel steel.
The second shield was a larger copper ashtray and a more ambitious conversion.
The center was worked the same way, but the contour from there to the
edge needed to be reversed. It originally had a flattened concave flare
and it took a lot of pounding to change it to a convex curve, like a hubcap.
I started near the center where there was a fairly acute bend and hammered
it out with the small side of a door hinge pin. From there, I worked out
to the edge using several other tools: the wider side of the hinge pin,
an Exacto knife handle (minus the screw on blade holder, a large steel
bearing and a couple different wooden stakes. You develop an instinct
about the particular stake you need to ease into the proper shaping of
an area. You also develop an instinct about the pounding technique; I
used a lot of very rapid low force tapping while dragging the stakes around
the piece at an angle, centered on the anvil. The instinct thing is hard
to explain, kind of like sculpting. I think what you're trying to avoid
is changing the shape too quickly and radically, as that might distort
the overall shape and introduce dents that would have to be worked out.
It's a gradual process.
Forgive me if I sound authoritative about this-- I'm not and my results
are far from perfect. I'm sure a real metal worker could do far better
and make mince meat out of my amateurish advice. I do feel that I caught
"the groove" of what I was trying to do-- it wasn't just random banging
with a hammer! Actually, the crude and imperfect hand-hammered look works
well in this case, similar to the effect of tarnished metal. The original
ashtray was too perfectly formed with concentric circles, like a cymbal.
This primitive genre is one where imperfection actually looks right at
home. That's probably why I like it so much.
03/18/01-- I gave Minx's spear to GFW and since I've already shown
you pics of the spear elsewhere, here's a pic of her replacement weapon. The
elastic doesn't have much ooomph, so I made sharpened metal arrowheads
to ensure that this would be a particularly unsafe toy. This was another one of those fun wood & metal time-killers.
03/24/01--
Once it's done, this is the sword GFW will probably end up with. It's like
I said earlier, once you start looking at historical stuff, you're drawn
to recreating it instead of just inventing it. With the shield and spear,
it's hard to ignore the fact that the figure looks quasi Greek/Roman, so
a grip tongue sword from that general period looks most appropriate. (Actually,
I think the way it works is that anything else looks weird because we're
used to seeing what we're used to seeing.) The blade's made from 16 gauge
welding steel with most of a couple hours spent trying to get the blasted
thing passably surfaced. This is a good way to get to know your Dremel bits,
even if you do end up wasting 'em. This time I did the hilt in putty because
its fine grain lends itself better to detail than wood does, and you can
knock it out in about 5-10 minutes. It'll prolly be painted an unimaginative
black/gray with some silver highlights to make the pinheads blend in better.
03/28/01--
The home stretch, at last. This has been one helluva long, drawn-out project
with about half the time spent waiting on UPS Ground Delivery. I should
have used that inbetween time more productively. With my rectifier back
in bidness, all that should have been remaining was the plating job
and the fitting of armor. Instead, I've got a bunch of silly little things
to do, like finishing the head, making a belt, the forearm armor and whatever
else... and finish the plating. I wisely did work on a few things though,
including the shields and swords shown above. I also made a leather scabbard
for the sword, shown attached in the Roman over-the-shoulder manner. I think
a belt-worn solution would look better but this was easier to deal with
considering the number of times the armor has been removed in test fits.
The tunic is a coarse woven cloth in a very simple "potato sack" style.
That's my kind of tailoring! The leather skirt thing is a little
more finalized, with metal buttons. The width of the straps isn't uniform
but it doesn't really bother me. I need to figure out a way of distressing
them though.
I don't know that you ever get better with electroforming if every piece you do is different. If you're unsure of the proper current, you have to ride shotgun over every piece you make, checking to make sure the copper is depositing acceptably. I haven't done a piece yet that's come out of the bath perfectly, and all have required extensive finishing and buffing. That's not fun. It's a nasty and lengthy process that's hard on a Dremel.
I've run the solution with an airstone to help with circulation problems,
but the deposition still isn't as uniform as I'd have liked. Visually,
the variation in thickness is not apparent. That wouldn't be a problem
if the pieces came out of the bath ready to rock. But they don't -- there's
always some surface granularity and discoloration. When removing those
surface imperfections, there's the possibility that you might grind through
the coating and not knowing where and how thick the deposit is doesn't
help. Forming an extra thick deposition should act as insurance, but the
gotcha is that thicker depositions have more opportunity to form
those surface imperfections that you'll need to fix. Besides, it takes
gobs of time to build up a really thick layer.
I've already christened a second bath of solution, just to see if I
could get better results. It worked better, but that's an expensive proposition,
and not really a (errr...) solution . Much smarter to figure out what
causes the problems and fix them-- Contaminated bath? Copper sludge? Finger
oil? Uneven thickness of conductive paint? That's the kind of stuff you
figure out through practice, which forms good working habits that you
eventually take for granted.
The sheen on the pieces is deliberately funkified. The electroformed
copper was finished smooth and gleamy, but the nickel plate was left as
it came out of the bath; the hazier the better. A few pieces were too
shiny and went back in the bath. It was really tempting to buff the pieces
to the reflective glaze since it does look neat and gratifying-- but as
I said earlier, in the context of the whole piece, it makes it look sort
of cheap. The hazy and uneven finish also serves a secondary purpose:
It masks small areas where the finish isn't quite so perfect. My comments
about grinding through the metal come from actual experience. If I'd been
trying to achieve the perfect & gleaming look, I'd have had to figure
out how to spot electroform to build up the imperfections and blend them
in. My quickie solution was to touch up with conductive paint and let
the final thin plating of nickel blend the coloration in. Those spots
aren't truly blended in and certainly wouldn't stand up to a round of
serious buffing.