Applying Patina

Lost Wax Casting Technique
The final bronze of the Monument will be created through the "lost wax casting technique." In the simplest terms: with the lost wax process an image is first sculpted in wax. Through a casting process the wax image is replaced with bronze. In this casting process an exact wax image of the sculpture is covered in a ceramic shell and then the wax is melted away in a oven. The hollow cavity of the ceramic shell or ludo mold left from the melted away wax is filled with bronze.

The original wax that the sculptor created for casting is lost during the melting away phase of this casting process, hence the name "lost wax casting" process. The original sculpted square, however, is preserved by first making a permanent rubber mold from the wax square, before it is covered in the ceramic shell. The original art therefore is never "lost", and can be reproduced perfectly from the rubber mold.

CAST IN BRONZE

Reaching out and looking up.
Embraced, enfolded, insecure.
Palm extended, fingers touch
Connecting at our soul.
Believed and relieved
Empowered, strengthened
To speak, to be visible
To be me.

Hummingbird
Kathryn Bolton

Cutting Into Manageable Pieces
The "Reaching Out" Monument size is much too large to fit through the studio loading dock doors at its Birch Avenue studio home. Also, the finished size of the Monument is much too large and too heavy for the foundry technicians to move it around for the initial bronze casting process. To deal with the Monument's cumbersome weight and size, before it leaves the studio the finished styrofoam and wax will be cut into approximately 70 cubes no larger than 30 x 40 inches on the sculpted surface.

Each of these pieces will have six quilt squares or will be sections of the sleeves, heads or hands of the two "Reaching Out" figures. The parting lines for the pieces will be along the centre lines of the quilt borders. When Michael Irving sculpted these borders he designed them to allow for the technicalities of cutting them up in wax and welding them back together once they become bronze.

The 70 styrofoam and wax cubes will be taken by truck to BLP Bronze in Toronto. BLP Bronze has been generious in making a donation of foundry casting for this first National Monument to survivors of child abuse.

Casting of the first
"Reaching Out" Monument
figure is taking place at the
BLP Foundry in Toronto
over 2005 and 2006.

Investment Mold
In the foundry the sculpted wax surface is covered in a ceramic material called casting investment to create a ludo mold or ceramic shell mold. The investment is something like plaster, but it dries into a hard ceramic-like shell. This rigid shell can withstand the high heat of molten bronze and the foundry burnout ovens and can allow the gases to escape that are emitted when coming into contact with the molten bronze.

To create the ceramic shell first the side of the wax with the detailed sculpted surface is covered in several layers of investment to a thickness of ½ inch. The first layer of the investment has to be put on with great care because it will pick up all the details of the sculpture. In order to prevent the investment from flaking or the ludo mold from cracking the next layer of the investment must be applied before the layer underneath completely dries.

When the investment is hard it initially helps to hold rigid the 5/16 inch sculpted wax sheet while the styrofoam support is removed from the back side of the wax. The styrofoam block on the back side of the wax is removed by melting away the styrofoam with a solvent, leaving a 5/16 x 30 x 40 inch piece of wax attached on one side to the ceramic investment.

Much preliminary work occures in
the foundry before the bronze
is heated to a molten metal.

Runners and Risers
The foundry technicians will plot out on the exposed back side of the wax plate, points to melt on a system of wax rods called runners and risers. When all the wax encased in the investment is melted away the runners will serve as channels for sending melted bronze to the sculpted surface and the risers will allow a route for heated air to escape.

The main runner is laid out so that the molten bronze will flow to the furthest corners of the piece first. Secondary runners coming off the main runner are planned so that molten bronze quickly and methodically fills the entire cavity in such a way that gases can efficiently escape and all the details and appendages of the sculpture can be filled before the molten bronze quickly hardens.

The risers in which gases escape are much narrower tubes than the runners. At the entry point for the molten bronze a larger hole called the pouring gate or pouring cup is created to connect to all the runners.

After the runners, risers and a pouring gate are set up, the back side of the wax sculpture and the runners and risers are covered in several layers of investment just as the detailed front side was. When the investment is dried the wax quilt squares, quilted borders and a number of runners and risers will be completely encased in a hard ceramic-like shell.

Burning Out Wax
To prepare for pouring the bronze into it, the investment shell mold with the wax inside is placed in a large oven with the openings of the runners and risers facing down. In the oven the wax is melted and burned away leaving a hot hollow investment shell. The hollow space of this shell is the exact detailed negative shape of what was once wax and what will soon be bronze. This is the stage where the wax is "lost" in the lost wax process.

All the moisture and wax must be melted out of the investment shell. The wax is melted out at 200 to 400 degrees Celsius, and then the temperature of the ceramic investment case is raised to more than 600 degrees Celsius to burn out any remaining wax or moisture. Even a small particle of wax remaining in the investment shell can turn to a gas in contact with the flowing molten bronze and flaw the sculptural detail that is being cast.

When completely melted and burned out, the hollow hot investment shell is taken out of the oven and placed in a large container with the openings of the runners and risers now facing up. The hot investment "container" is quickly surrounded in a fireproof and heat resistant sand to help the ceramic mold stay rigid and to absorb any bronze that leaks out of any cracks. Immediately molten bronze is poured into the hollow space of the hot investment shell.

 

TURNED TO STONE

The pain is too large
It radiates in my bones.
The darkness is so deep
I’m curled up all alone.

I long to see the sun
To heal and warm my pain;
I’d even settle for clouds
or sheets of pouring rain.

In this dark cold room
Where all my hope is lost,
I sit so very still
Knowing this has a cost.

Slowly the door opens,
A shaft of sunlight comes in;
Hesitantly I crawl out,
Now my healing can begin.

In plaster, wood and wax
I lay my broken life down,
Realizing with each small step,
I’ve finally come into my own.

Cherlyn

Properties of Bronze
While the wax is being melted and burnt out of the ceramic shell mold, another oven is melting the bronze in a crucible or pot that is heated to more than 1100 degrees Celsius. Bronze historically has been roughly 90 percent copper and 10 percent some combination of tin with possibly some zinc and lead. Copper is a very soft metal, but it withstands the elements of the weather and time quite well. Copper does not pour well when molten, but when tin is combined with copper it flows better, becomes a harder metal, and some believe becomes more attractive.

In the foundry process, gases from the molten metal are created in the melting process and these can leave an uneven and pitted surface when the bronze is poured into the ceramic shell. Copper/phosphate and other powders were historically added to bronze to remedy this problem.

Modern bronze foundries have developed silicon bronze as an art bronze that is durable over time, aesthetic, easy pouring and is resistant to the pitting associated with foundry gases. This modern silicon bronze is an alloy that addresses the many different and complex properties of an art bronze. The Everdur silicone bronze for the "Reaching Out" figures is approximately 94 percent copper, 4 percent silicon, 1 percent manganese, with the remainder tin, lead, zinc, nickel, iron and aluminum.

ALL THE GOOD I CAN DO

You can't have it -
not my happiness
not my love
not my life fulfillment
not my security
not my commitment
not my success
not my purpose
not my foundation
You have not, can not, will not take from
Me my potential to have all of these things.

To be free from fear
from betrayal
from control
from limitations
from you & your dementia

I can be loved
I am loved.

My chance to be remembered
for all the good I can do
for all the support I can give
for all the hope I can bring
Comes from you and all you did.
Fooled you !

Jessica

Pouring the Bronze
When the bronze is melted to the right temperature the red molten metal is brought out of the oven. The manganese in the bronze serves as a deoxidizer to help separate gases and other impurities from the molten bronze that would weaken the sculpture and create visual flaws. The impurities that float to the surface are scraped off with steel tongs. Pouring of molten bronze is the dramatic moment in the overall foundry process that will actually take more than one year in total for the "Reaching Out" Monument.

The crucible with bright melted bronze is brought over to the ceramic mold and is immediately poured quickly and consistently into the prepared pouring gate of the ceramic investment mold. The bronze is poured while the ceramic mold is still hot, so the bronze will not solidify before filling all the areas and crevices of the mold.

The molten bronze is poured without the slightest interruption, because a momentary pause or jerk can cause an air bubble to form in a runner that will become a hollow flaw in the bronze sculpture.

The bronze cools to the point of solidity within minutes, but it will be hours or overnight before the bronze is safe to be handled. The space that was first wax, then a hollow cavity, is now filled with solid bronze.

Removing the Shell
While the investment shell and bronze cool the metal shrinks almost 10 percent and the shrinkage and dramatic change in temperature causes much of the investment shell to shatter into pieces that come away from the now bronze quilt squares. Ceramic investment that does not fall away will be chipped away from the bronze with hammer or chisels. All of the runners and risers are cut off and ground smooth.

WORLDS

In my worlds
great voids exist
In my dreams
no release
Freedom travels with the breeze
In the sky, with the wind
In the air which is everywhere
In my world.

Babette Forget-Healy

Welding, Grinding and Chasing

This process with the 70 wax and styrofoam cubes is repeated 70 times to change the wax surface with all their details into bronze pieces. The after casting clusters of bronze quilt squares, and hands, sleeves and heads of the two "Reaching Out" figures will be organized and welded together.

The weld lines leave ridges which will need to be ground down and textured to look like the rest of the surface of the quilt borders. Some areas of the weld, particularly at the squares where the borders come together, will need to have some of the original detail resculpted with chisels and fine grinders.

Fixing Imperfect Castings
If all turns out right in the casting process, all of the detail sculpted will be found in the cast quilt squares. In a sculpture the size and complexity of the "Reaching Out" monument there are likely to be some small sections where the bronze did not flow or where the investment shell cracked. This will leave small missing voids or areas of imperfection that will have to be replaced.

The small flawed areas will have a new casting wax piece made from the original rubber molds and the entire investment and bronze casting process will be repeated with this small replacement section of the sculpture.

Applying Patina
After all the pieces of the Monument are welded and cleaned up, the colour or "bronze patina" will be applied. Patina is the colour that naturally takes place on raw bronze as it ages over a long period of time. Sculptors short cut the patina aging process and gain far more control of the patina color through the application of various chemicals on heated bronze. The patina is slowly built up to a rich colour through the repeated application of various chemical solutions accompanied with heat.

In the year that the "Reaching Out" figure is moving through the foundry process, numerous test pieces will be done to experiment with a patina process and colour that will allow the plain quilt squares to be used for making hand prints with damp hands. After the right patina colour is arrived at, it is brought out further with the application of a paste wax.

THREAD OF HOPE

Oh my soul screams in silence
I weep...my loss is so deep
Torn, ripped and thrown away
I am forgotten...no place in your world
Drowned in an instant - a moment lost forever
Holding on --- letting go
Suspended by a thread of hope
From hell to here -- here to the future
Anticipation - unknown

Tracy