you are here [x]: Scarlet Star Studios > the Scarlet Letters > choice of metal for armatures
<< before
intermission
after >>
planning a steel armature
May 30, 2006
choice of metal for armatures
by sven at 8:00 am
It appears that there are mainly just four metals used in creating metal-jointed armatures:
- Brass: Easy to find, easy to cut, easy to braze. Seems only to be used in amateurs' armatures. Reacts badly with foam latex, due to there being copper in the alloy. The armature can be wrapped or sprayed to protect the latex, but it's still a risk.
- Steel: A strong material, but rather heavy. More difficult to find -- need to go to professional metal suppliers, rather than hobby stores. Brazes easily. Can be used safely with foam latex. Sparks when cut.
- Aluminum: Lightweight. More difficult to find -- need to go to professional metal suppliers, rather than hobby stores. "Cannot" be brazed; pieces are generally secured using very small screws (4-40 or smaller). Typically requires a milling machine -- not just drilling and cutting. Aluminum balls not recommended for ball joints: too soft. Can be used safely with foam latex.
- Phosphor bronze: Noted as having a particularly "smooth" feel. Material is difficult to find -- needs to be special-ordered, even from a pro metal supplier. Reacts badly with foam latex, due to there being copper in alloy. Even among professional armaturists, it seems esoteric; its use may (?) have come from the Trnka studio.
If you want to make armatures at the pro-level, steel seems to be the standard. I suspect that this is primarily due to it being safe for use with latex. Aluminum has the advantage of being lighter -- but this is counterbalanced by the fact that it's difficult/impossible to braze.
I'm in the process of collecting the materials that I'll need for making a steel armature. Even if I'm just a hobbyist, I'd like to do pro-quality work. And I'm interested in steel just for the sake of experiencing different materials hands-on.
However, I've begun to question the assumption that steel is necessarily superior to brass. If I understand correctly, brass works fine with silicone. Brass is easier to find than steel, and doesn't spark when you cut it. So, if you're making silicone puppets, shouldn't brass be the preferred material?
I have a suspicion... For a very long time, foam latex was the pinnacle of pro puppet-making. Foam latex puppets require steel armatures. Silicone is relatively new on the scene. I suspect that people still feel that steel is the "professional" and "superior" material -- but only because they haven't disentangled the actual needs of the casting materials from what kind of armature is required.
I was very interested to read this on an SMA thread:
[Henry] Selick recently mentioned, in an interview relating to his work on "Life Aquatic", that he's basically abandoned foam latex in favor of Dragon Skin, which is silicone based, I believe.
It looks like silicone may be the future. ...Perhaps brass is the future, too?
posted by sven | May 30, 2006 8:00 AM | comments (6) | categories: stopmo
Comments
I must be prescient. I wrote this post (and the past two) a few days ago, just before finding out that Mike had started his excellent thread about silicone over at SMA. :-)
Posted by: sven at May 30, 2006 10:37 AM
Couldn't you dip your brass armature in liquid silicone a few times before placing it into the mold as you cast foam latex. Voila, no negative chemical interaction?
Posted by: shelley Noble at May 30, 2006 10:40 AM
Have you all seen this: http://www.montereymotiongraphics.com/armatures/
Posted by: DG at May 30, 2006 9:27 PM
Hey DG --
Yeah, I've seen that link -- it helped me a lot when I was designing the Ambassature. It's the only tutorial on making brass ball-jointed armatures that I've seen.
Actually, at this point, I only know of three online tutorials about how to make ball joints: the one you mention, LIO's, and this one: http://www.limanima.com/
Thanks for mentioning the link -- and if you find more, please do pass them on!
Posted by: sven at May 30, 2006 11:00 PM
Hey Shelley --
In principle, I think dipping the armature in silicone ought to do the trick.
Two potential problems, though. First, is that you're going to have to protect the ball joints from getting gummed up with the silicone by wrapping them. Second, silicone's so damned expensive, it's going to be awkward to make a big enough batch to do dipping in. Might be possible to brush it on, rather than dipping the whole thing in...
As I understand it, the typical way to protect latex from brass armature parts is to wrap them with teflon tape and/or spray them with... um, I forget what kind of spray was recommended. Something that's functionally similar to spray primer.
I just purchased some teflon tape this week -- I'm surprised at how delicate it is. Sort of like the material that white trash bags are made of, but more gossamer. Found it at Ace Hardware, right next to the plumber's epoxy putty (for only 99ยข). It looks like it will bend with an armature's joints quite nicely.
Posted by: sven at May 30, 2006 11:12 PM
Thanks to you and D.G. for the Monterey link, that was very helpful. I was going to mention pre-drilled nickel-plated lamp balls but was waiting to try them out first. The Monterey method may be suitable for me as I'm not gung-ho for armature building itself and just want something serviceable. Seeing that tutorial gave me me a way to imagine my doing it myself for the first time.
Posted by: shelley Noble at May 31, 2006 12:54 PM