Duluth Public Art Progress, 13 April

Making good progress on the project. We are being extra careful on the mold making and adding insurance in the form of sand molds over our ceramic shell. This adds perhaps another hour per mold but insures we don't have to start from scratch if a mold fails.

Final 3 sections of the legs, all the debris in the background is waste. But if one of our shell molds were to fail we would not only have 30 pounds of molten bronze on the floor we would have to start the wax process over. The sand mold is insurance to prevent this from happening.

Make shift blower. To dry the shell cores (inside the mold). I found a sleep apnea pressure device that blows a gentle 8 cfm, split the pipe and put ends into mold. Works great!

Arms right out of the molds

Body section, because these are so big we are coating one side at a time. To prevent the wax from spreading out from the weight of the mold material screws are set next to the wax, blocks are underneath.

We will be casting body sections early next week and assembling of the casting will start right after that. By next weekend I should have the female figure pieced together, can't wait!

Duluth Public Art Faces and more

The female officers face

male officer

arm sections in the ceramic shell room with the first coat of liquid

The pictures of the faces are taken after the initial clean up and a quick sand blast. I'm pleased with how well the castings came out. The final 3 sections of legs are in the kiln and should be ready for a bronze pour tomorrow. The arms are in the first coat of the ceramic shell process.

Here at Last Chance Fabricating we use a product called Shellspen. It is a very good product and makes the process easier because we don't have to keep our liquid silica mix in constant agitation. I did this for a number of years with an elaborate mixing machine and lots of difficulty if the power went out.

Duluth Project Update

the wax heads ready for ceramic shell process

back of sections, the red wax, called sprues, act to channel the molten bronze to the pattern

the pieces after the first dip in the liquid silica 

second dip of liquid, allowed to drip off the excess

subsequent dips of liquid are followed by dry coats of stucco in progressively coarse grades  with 10 coats total

the completed refractory shells are now de-waxed, creating a cavity in the mold where the wax was

molds are placed in the kiln and brought up to 1800 degrees, that temp is held for one hour to vitrify the molds making them strong enough for the 2100 degree bronze

Man's face right after breaking away the mold

woman's face

It has been a busy couple of weeks around the studio. We have poured three times with good results in spite of having my pyrometer (used to check the temperature of the molten bronze) die on me. Other troubles have been four trips to the dentist for a problem tooth and infection and smashing my head on a sculpture resulting in a gash on my forehead. Just your average times at the sculpture studio.  I am, however, very pleased at the outcome of our efforts.

Ceramic Shell Molds

Here are 10 of the more than 30 molds we will need for the Duluth Public Art Project.
These are 3 leg sections (2 have been completed) and the badges and arm patches. These molds are half way through the dipping and stuccoing procedure. Next round of molds I will take a few more pictures to help explain the process.
When these are finished we will start pouring bronze and should be pouring twice a week for the next 4 weeks.

Preparing waxes for investment

Lester doing wax work

body sections, some with sprues added

wax heads and arms

The past two weeks Lester has been using the molds we created from the clay figures. He is brushing wax into the molds to create the hollow wax copy of the original sculpture. The red tubes you see in the pictures are wax as well. The red wax creates a system to introduce bronze into the pattern (sprues)  and to evacuate the air as the bronze is poured in (vents). I have been sculpting the patterns for the details, badges and shirt patches.

Polytek Spray mold system

Removing metal shims, you can see the flange dividing the figure in half.  After this step we sprayed on the rubber mold material.

Here I am prepared to spray on the plastic mother mold. Note two red pegs sticking up on the figure. Lester had the idea of using rubber grommets embedded in the plastic to help facilitate removal of the mold.

Spraying action shot. The loaded gun weighs almost 15 pounds. It was worth while to build the figures to be able to lay them down horizontally. Much easier to spray down and much less over spray.

Lester using air pressure to help release the mold.

Mold sections, even though we used air pressure to release we ended up peeling clay off the armature. Actually , this works very well as it's easier to reclaim the clay.

Of the 20 molds we made this way we only broke one. The plastic material was easily repaired with a 2 part epoxy made for plastic repair.

The face after peeling off the mold. This scrapes off the ears and damages the figure. No matter the molds are perfect.

These are photos of  the female figure taken over the last two days. It shows how we are using the Polytek Spray Mold making system.

A more feminine Deputy

A much less bulky body, thinner face and more friendly expression although the harsh light hitting her face isn't the most flattering. Her pony tail doesn't show here either. If you look back in the blog the difference is apparent.