Thursday, November 19, 2009

Bronze Casting – Sand Method

Last weekend we witnessed an actual bronze casting.  Bob Darr our teacher at the Arques Wooden Boat School set up the air blast propane forge.  Simply put it is the bottom third of a 55 gallon drum that is partially filled with a special cement, an inch and a half pipe is set at an angle and functions as the fuel input into the forge.

 

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For the bronze stock, Bob tried out an old propeller shaft, which Alex cut up into small three inch pieces.  When heated, to approximately 1800 – 2000 degrees Fahrenheit

Bronze Casting

The bronze melted in about 45 minutes, and by using a modified carpenters square, the ash and impurites are skimmed off the surface.  The alloy was also seen to be burned off, as seen by a green glow to the top of the forge. 

Bronze Casting

Two people then hold the crucible and pour the liquid bronze into the forms.

Bronze Casting

Flasks are only opened the next day, to ensure that the minimum amount of the expensive petrobond sand is not burned.  Here is Alex’s bronze dolly ( used for riveting and clinching boat nails and roves )

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Unfortunately the last flask was not a great success, as the bronze was cooling down by the forth pour ( each pore was about 2 minutes ), here one can see the bronze cooled before it reached the extent of the cavity in the form.

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Bronze Casting

Here is Alex’s finished dolly.  He opted not to patina it, but michael did, using phamarcy bought peroxide and wine vinegar heated with a blowtorch.

Here is some other items Bob wanted, a mast step’s support and a bow post cap.

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( Added later a link to a ‘safer’ version of Petrobond is something called K-Bond )

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