Finished

BYU's spring term ended Thursday. It is great to be done. Both of our tests and presentations went well. Here are the finished sculptures. The broken glass came out of the kiln this morning...the cracks sealed up alright, but new cracks formed. Oh well.
This one is called The Roots of Growth.
It feels good to be done.

Rough Day

Some days are just rough...but they always get better.
It started this morning when I went to finish my sculpture pieces (the final is on Thursday).
I had filled these rubber molds with a amber resin and we were going to just pop them out and make some more....well no popping occurred. They were stuck fast to the rubber. We practically tore them out. As you can imagine the molds didn't like this... ripping chunks out of the molds and all. Ruining molds, great way to start the day.
Then I spent at least 2 hours grinding my glass piece. It had some problems last week that I was trying to fix today. The piece had cracked and so I was going to re-fire it in order to seal the cracks. But first I had to remove a large chunk of glass from the back so that it lay flat. But... to grind glass, it must always be wet. So you use a water grinder, which is a grinder that sprays water everywhere. So now I'm wet, very wet, but my piece is ground flat. Yay!BUT, before I can put it back in the kiln, I have to fill the back up with plaster so that it doesn't lose its shape when it gets hot. No problems there. Then we go to lift it up and ... chink (or whatever sound glass makes when it cracks in half) and the right side of the body falls off. So now you think I'm just paranoid when I say I see the plaster cracking on the left side of the body- well no, the glass is cracked all the way through now too, I just don't dare move it so it hasn't broken off yet. Now that the glass is very broken, we are still going to try to melt it back together but there are no guarantees that it will work or even look good. That was very frustrating.
But days always get better. Thanks Mark for cheering me up and helping me relax.

Step 7: The Finish

To finish the piece, we cut it away from the sprue, grind down what is left of the sprue connection, grind texture into where the connection was to hide the connection, and patina the piece. Sandblasting happens between most of these steps and a lot during the grinding steps. Sandblasting helps even out the texture and makes the piece more uniform. It also creates a slight texture for the patina to stick to. The patina is a chemical/heat treatment that oxidizes the bronze. Different chemicals will make different colors on the bronze. The lighter colored pieces in the pictures are the pre-patina, freshly sandblasted color of the bronze. This color does not last long. The finally completed statuettes are the darker pieces. Ignore the stone. I was just playing around with compiling them together somehow, but I decided against it.

Step 6: The Unveiling

As the bronze cools, it shrinks. This cracks the shell a little, but we then take a hammer and pretty much whack the base of the sprue. Most of the shell breaks off during this part mostly because of the vibrations through the metal. The rest I chisel off.

Step 5: The Pour

The pour is the shortest step in the process. Once everything is set up it takes about 5-7 minutes to pour the pieces. Using specialized tongs we lift the crucible out of the furnace and set it into the contraption to pour. The gunk on top is scraped off (dirt, old shell, and other impurities). Then we lift up the crucible and start pouring. Thin pieces first, thick pieces last. If a shell happens to break open from the weight of the bronze, sand is placed around the shell and it is left to cool for a minute or so before adding more bronze. Fortunately that didn't happen to me. The left over bronze is poured into a block. And we're done.

Step 4: The Preparation

The Preparation isn't quite a good name for this step, because everything else was done in preparation to pour the bronze. However, this step is done right before the pour to prepare for the pour to happen right after unlike the previous steps which can happen days, weeks, months or years before the actual pour.
About 3 hours before the pour happens the shells are loaded into a big gas furnace (the big black furnace). The wax melts and drips out of the bottom. The hot wax also gets absorbed into the shell. For 3 hours, the shell is then heated so that the wax burns out of the shell completely. The heat also finished drying and curing the shell so that it is strong and ready for bronze.
Meanwhile, chunks of bronze are converted into glowing boiling molten bronze. The bronze is heated in a crucible in a separate furnace (the small orange one). This takes the bronze up to 2100°F.
About 10 minutes to the pour, we get dressed. This means heat resistant pants and jacket (over a thick leather welding jacket), really thick gloves, and a face mask. Very stylish.
Once dressed, we take the empty, now hollow, shells out of the furnace using big tongs. These get placed in a sandbox "right-side up". In order to flip these around, I had to use a second set of gloves like oven mitts- the shells were singeing them. Sand is scooped up around the base of the shell to keep it from tipping over.
Now we are ready to pour.

Step 3: The Slurry

The next step involves making a strong silica based shell around the wax sprue. After coating the wax with floor wax, I dip the whole sprue into the silica based slurry and then coat it with a silica based sand. The first 3 dips are coated with a very fine sand so that the details and texture of my piece are molded. The next 5 dips use a coarse sand so that the shell is strong. The last dip uses no sand. Each dip requires 6-8 hours to dry before it can be dipped again. The shell is hard, brittle, and has the negative mold of my piece.
In the middle picture, the sprue has only one dip completed. In the other two pictures, the same sprue has been dipped all 9 times.

Step 2: The Sprue

After the wax is perfectly the way I want it, I build a sprue. This consists of wax "pipes".Using a soldering iron, I connect the gates (the pipes) to my piece. This sprue is the path that molten bronze will take to fill the piece. Notice the cup on the bottom, that is were we pour the bronze. The greenish wax is a "nose guard" to prevent the leg of my sculpture from getting bumped and breaking off. Gates have to be attached so that the bronze can fill from the bottom (or near the bottom) and air can excape out of the top as the bronze goes in. This will be more clear after the next step.

Bronze Sculpting 101, Step 1: The Wax

In my figure sculpting class this spring, I am doing a lot of bronze casting, and loving it. Over the next week or so I will attempt to explain how this process is done (using the Lost Wax Method).

Step 1: The Wax

First we create our sculpture in wax. (Or Step 0 and Step .5 can be done first in which the sculpture is made is clay and then a mold is made into which the wax is poured). My wax sculptures are small human figurines, which we call gestures. These are made exactly as you want the final bronze piece to look like. Thanks to the models who hold these for about 3 hours (with small breaks) so that we can sculpt from life.