Making Statues
October 30, 2008 11:12 AM   Subscribe

Making the Sculpture. Tom Otterness, the guy behind those sculptures that make riding the A almost bearable (aka Life Underground), explains how bronze casting is done in a way even an idjit like me can understand.
posted by dame (15 comments total) 8 users marked this as a favorite
Thanks for posting this, it easily illustrated a process I've idly wondered about in the past, but never had the motivation to actually learn about. Good information.
posted by owtytrof at 11:25 AM on October 30, 2008

Nice to finally have this adorable enigma explained.
posted by nanojath at 11:36 AM on October 30, 2008

He needs to make some sculptures for the 7 line, except instead of little people he can make life size and functional bronze subway cars that they add on to the 7 train so that people can get in them and relieve some of the insane congestion on that train.
posted by shmegegge at 11:36 AM on October 30, 2008

There's a How It's Made episode that covers bronze statues, but it is if anything less clear and comprehensive than these line drawings | photographs.

One of my kids is very interested in art and thought it was pretty hilarious how many positive/negative/positive/negative transitions a casting has to go through.
posted by DU at 11:40 AM on October 30, 2008

Don't miss his masterpiece, the "World Trade Center" sculpture garden in the Battery City Park, or Rockefeller park, or what ever they call it nowadays. Take the subway to Chambers and walk west until you hit the river. It's right there, well worth the trip. Best. Public. Art. Evar.
posted by StickyCarpet at 11:48 AM on October 30, 2008

I used to work in a bronze foundry and that is pretty much spot on. It seems quite simple according to the explanation. It gets a little more complicated when it is a large statue. Countless hours are spent welding, grinding, cutting, etc.

For instance, it took 14 months from the original sculpture to finished project to make this, with a crew of five.
posted by chugg at 12:13 PM on October 30, 2008

Oh yeah! I briefly glimpsed some of those passing through a station on my first visit to NYC last month. Forgot about them until now.
posted by anazgnos at 12:19 PM on October 30, 2008

shmegegge, just move to the L. Sure it is almost as crowded, but the people rubbing you might be sexy!
posted by dame at 12:25 PM on October 30, 2008

This was totally delightful. Thanks, dame.
posted by andromache at 1:36 PM on October 30, 2008

There's an excellent book on the subject:
From Clay to Bronze by Tuck Langland

I also recommend
The Mouldmaker's Handbook (note anglo-spelling of "Moldmaking") by Jean-Pierre Delpech et. al. along with anything on modeling by Bruno Lucchesi.

Note that if you work directly in wax, the foundry can directly make a bronze from that. But moldmaking is still a good step, so that you can do multiples, repairs/replacements, and so on.

As an interesting development, there is also bronze clay, discussed and reinvented in this forum thread. This is a mix of powdered bronze metal and a bit of wax or clay. You can hand shape this or pour it in a rubber mold and then pack it in aluminum oxide and fire it in a furnace, sintering the metal particles into a solid mass. You end up with a bronze sculpture just like from the lost wax process. This new technology may be easier to do, effort and equipment-wise, compared to lost wax. (Essentially, it's like firing a pot; you don't need to melt bronze in a crucible and pour it.)

(Rio Grande sells bronze clay in 100 gm and 200 gm quantities, but there are instructions in the thread on making your own.)

For people interested in making this type of sculpture, I highly recommend finding a course on casting-moldmaking at a local community college, art school, or community center. Moldmaking can be complicated and expensive, a bit of expert help is worth it.
posted by sebastienbailard at 2:19 PM on October 30, 2008

If anybody is thinking of making a one-off lost wax sculpture, you can cut your foundry cost down by keeping it smallish, using "victory brown" wax and by using a copper wire as an armature. By working in wax, the ceramic shell can be applied directly to your original and the copper wires can be left inside. It eliminates the expense of steps 9 and 10.
posted by bonobothegreat at 2:22 PM on October 30, 2008

shmegegge, just move to the L. Sure it is almost as crowded, but the people rubbing you might be sexy!

oh, if only it could take me directly to woodside. such is life.
posted by shmegegge at 3:10 PM on October 30, 2008

Neat. Here's an idea: you could use a CNC router to carve Chavant clay (or one of a number of other materials, such as plasticine, polystyrene foam, or polymorph pellets). After carving, smooth it out on the clay rather than waiting to smooth on the bronze. Carving at a lower resolution, ie with a larger tool, is much faster, so if there are areas on your model where you can do this, it's worth it. You can machine or manually add the pouring cone and the runners, then pour the ceramic, then pour the bronze.

Since a 3-axis router (think of it as a plotter with a high-speed drill) produces 2.5D work, the router method naturally lends itself to "slice and join", ie carve the back and the front of the work, then join them together by melting the wax on the flat surfaces. Again this will be significantly easier to do in the wax than in the bronze.

You could carve the two halves of the mold directly with a router, but this would require you to carve something with a higher melting point and hardness than the end product. Steel would be the obvious choice, but machining steel is slow and takes very high-grade tools (and accordingly is very much more expensive). Aluminium would be easier to machine but I don't know if you can carve a bronze casting mold out of aluminium.

If you wanted to mass-produce your object, you could carve the halves of the mold with the router out of Chavant clay, then cast the molds in bronze, then use the bronze molds to cast plastic or plaster or potters' clay.

Sigh ... I'm not getting my router 'til January ... counting down the days. :D
posted by aeschenkarnos at 5:26 PM on October 30, 2008

Nice, an Otterness piece was just installed this week in Otterness' home town of Wichita at the Wichita State University. The Millipede!
posted by thylacine at 7:47 PM on October 30, 2008

Cool post.

I live right above the 14th and 8th stop and its hands down my favorite subway station in the city. I've always been a big fan of Otterness' stuff - its easy for an untrained hand like mine to sketch them.
posted by allkindsoftime at 11:44 AM on October 31, 2008

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