My friend Jenna sent me a care package of bones. I immediately started putting them in mold boxes and pouring silicone.
These are basic open mold investment castings. To make these, I am keeping one whole side of the model open to the air; it means I have a lot less to worry about regarding pressure buildup and steam explosions, etc. I’m pretty comfortable with that, really – exploding splats of molten silver sound like no fun at all.
Investment casters use a steel “flask” that they position the wax model in, then surround with plaster (“investment”) then they heat the flask until the wax soaks into the plaster leaving a hole. You then pour molten metal into a port that leads to the hole. For 360-degree objects instead of open molds like mine, you need a centrifugal pouring system or a vacuum system to suck the metal into all the corners of the mold. I’ll be doing vacuum molding eventually, as soon as my hot shed it done and I can build my casting table. In the meantime I am really happy with the open molds, though let me mention that those can be mighty intimidating when the silver starts bubbling and hissing and I run across the room and hide, wondering if it’s going to belch at me.
I got a couple of feet of steel square tubing (3×3″, 4×4″ and 4×6″) and let Mr Happy Dancing Bandsaw turn them into flasks of varying depths. It’s really incredible how efficient you can get at building stuff when you have the right gear: the bandsaw does its work while I clean up the razor-sharp edges of the previous cut-off, using a flap wheel on an angle grinder. Total effort to make a flask, for me, is on the order of 60 seconds, most of which is walking across my shop.
You’ve already seen this; this is just a better photo:
Then there’s the fox femur:
Because the molds are open, I have to sand/file down the back and shape it to look about right. The rest is polishing. Polishing is a great big pain. “Real” casters use a tumbling system with stainless steel ball bearings to peen and hammer away the textured surface. I use 2000 grit sandpaper and steel wool and silver polish, and my thumbs hate me for it. But the results are absurdly satisfying.
The vertebra took 4 troy ounces of silver and about 2 of tin. It’s heavy, sleek, complex, and satisfying. I have some tapered carbon fiber rods (i.e.: golf club sticks) and have been thinking of filling the top of one with epoxy, screwing in a 304 stainless steel pipe fitting as a ferrule, and making a threaded adapter to attach one of these onto it. You’ve got to admit a black carbon fiber walking cane with a silver vertebra: that’s mighty tactical.
I’m waiting to see how the cat skull turns out, though.
I’m going to put one of the fox legbones and the skulls up for an FTB benefit auction. I don’t know about the vertebra – it’s about 5 hours of polishing and my poor aching thumbs say “no!” I suppose I could release one of these in “you polish it!” condition (including steel wool and 2000-grit sand paper!) but that seems cheesy. I’m also concerned that there’s a lot of silver in that; I would have to set a minimum bid. Then again, I could just as easily whip up some bronze. OK, that’s scary “I’ll just melt up some bronze” is not a normal thing for a person to say.
Product photography notes: This was done with one huge softbox (to camera right, looking over my shoulder) and a smaller spotlight to camera forward right to pop the objects off the background. You ought to be able to “read” the locations of the lights by looking at the specular highlights in the silver and the shadows on the leather. I have actually not moved the lights in my studio for months – all I did was throw the motorcycle jacket on my little wheeled stage-stand and drop the silver objects onto it in cunning position. I switched to the jacket because the silver will reflect the black of the leather and really pop the contrast, and it does. I also positioned the jacket so that the zippers made a hopefully interesting composition which also “sell” the size of the object. By using the same background for all 3 objects I am not being lazy: I am representing the proportional sizes of the pieces. And I’m lazy. Speaking of lazy: you’ll also notice how the rear spotlight creates a hotspot that sort of vignettes the whole image without my having to do any photoshop. I love photoshop and have spent months of my life in it, but the best photos are ones you can use right off the camera, because lazy.
Mr Happy Dancing bandsaw’s coolant recirculation drain blocked up with chips the other day and it vomited a bunch of coolant oil in the floor. This is how we learn what things have to go on the preventive maintenance list.