Bronze casting
Over the last few months I've been taking a bronze casting class at the Pratt Fine Arts Center. It was a lot of fun, so I thought I'd share some pics here.
Lacking any specific project, I got a version of my Attoparsec logo laser cut out of plywood to serve as the positive for a wall plaque. The first step was to turn this into a wax positive by means of a silicone mold. We used a great technique which uses silicone caulk, which is considerably cheaper than 2 part silicone RTV. Learning that alone justified the class for me!
I ran out of time to make enough in class, so I hit Goodwill for an old crockpot and cast another couple wax positives at home.
Also done at home, because it takes hours and hours, was creating a sprue tree and attaching the wax positives. This is done with commercial sprue wax, which comes in various widths. The trick is getting a very solid bond, which means poking it with a soldering iron to fuse both sides of the joint. This is complicated by the fact that the sprue wax is hollow -- poke too deep and you'll hit the void, letting all the molten wax drain away from the joint!
This is why the joints have to be solid -- it has to support itself and the wax positives. And then you have to drive it to the art studio!
We made temporary molds for the plaster investment using chicken wire and tar paper. Our wax positives, and their sprue trees, we embedded in there in investment plaster. We mixed that up in 5 gallon buckets, 2:1 sand:plaster. Forms of this size took about 4 buckets and weighed 300 pounds.
The plaster forms were loaded into the kiln, with the sprue openings pointing down. These were heated up over several days to melt and burn out all the wax, leaving negative space in the shape of the wax positives.
On the night of the casting, we first had to dig out the sand pit in the casting room. The forms were then removed from the kiln (still around 150 F) and burried so their tops were at the same level. This makes pouring easier, and (more importantly) contains any spills should they crack.
The pour! There is nothing, absolutely nothing, as beautiful as molten metal.
The plaster forms were pulled out and taken outside, where we cracked them open. They were, of course, still quite hot at this point. Mine spit quite nicely, due to the regular planes of the plaques. You can see the design very plainly here, where the oils left on the surface burned into the plaster during the pour.
This is what mine looked like once fully cleaned up. This involved hitting it with a pressure washer, which flashed into steam, kicking back burning grit into my face. Fun!
And, after cleaning them up a bit more and using a patina process, this is what mine ended up as. One is now on the wall of my shop. I have no idea what I'll do with the others -- I didn't expect them all to come out!
Lacking any specific project, I got a version of my Attoparsec logo laser cut out of plywood to serve as the positive for a wall plaque. The first step was to turn this into a wax positive by means of a silicone mold. We used a great technique which uses silicone caulk, which is considerably cheaper than 2 part silicone RTV. Learning that alone justified the class for me!
I ran out of time to make enough in class, so I hit Goodwill for an old crockpot and cast another couple wax positives at home.
Also done at home, because it takes hours and hours, was creating a sprue tree and attaching the wax positives. This is done with commercial sprue wax, which comes in various widths. The trick is getting a very solid bond, which means poking it with a soldering iron to fuse both sides of the joint. This is complicated by the fact that the sprue wax is hollow -- poke too deep and you'll hit the void, letting all the molten wax drain away from the joint!
This is why the joints have to be solid -- it has to support itself and the wax positives. And then you have to drive it to the art studio!
We made temporary molds for the plaster investment using chicken wire and tar paper. Our wax positives, and their sprue trees, we embedded in there in investment plaster. We mixed that up in 5 gallon buckets, 2:1 sand:plaster. Forms of this size took about 4 buckets and weighed 300 pounds.
The plaster forms were loaded into the kiln, with the sprue openings pointing down. These were heated up over several days to melt and burn out all the wax, leaving negative space in the shape of the wax positives.
On the night of the casting, we first had to dig out the sand pit in the casting room. The forms were then removed from the kiln (still around 150 F) and burried so their tops were at the same level. This makes pouring easier, and (more importantly) contains any spills should they crack.
The pour! There is nothing, absolutely nothing, as beautiful as molten metal.
The plaster forms were pulled out and taken outside, where we cracked them open. They were, of course, still quite hot at this point. Mine spit quite nicely, due to the regular planes of the plaques. You can see the design very plainly here, where the oils left on the surface burned into the plaster during the pour.
This is what mine looked like once fully cleaned up. This involved hitting it with a pressure washer, which flashed into steam, kicking back burning grit into my face. Fun!
And, after cleaning them up a bit more and using a patina process, this is what mine ended up as. One is now on the wall of my shop. I have no idea what I'll do with the others -- I didn't expect them all to come out!