Monday, March 10, 2008

Assigned Reading-McCreight Ch. 4-Burnout and Melting

The purpose of the burnout is to evacuate the mold, cure the mold, and heat the mold to the proper temperature.
Allow 2-3 hours for mold to dry before burnout. The steam removal method is practical for soft waxes.

Burnout Equipment-kiln, long tongs, thick work gloves, high temp. nichrome wire, ventilation system, flask hook
To burn out in a kiln-remove when wax stops dripping out, then turn kiln up to vaporize any remaining residue.

Prep.-take off base, clear sprue area if not already visible.

Position-raise the flask slightly off the mesh with nail or coat hanger wire.

Burnout-set kiln to medium.

Fast Method-check every half hour until complete (when sooty black stain is gone)

Right Method-3 hour cycle 5 hour cycle
1@ 300 deg 2@ 700deg
1/2@ 700 deg 1 1/2@300 deg
1/2@1250deg 1@1000 deg
1/2@ 1250 deg

Do Not Overheat
wax vaporizes at 1250 degrees and at 1300 degrees the gypsum begins to break down.

It is important to avoid oxides from forming to prevent pits and staining-flux works well to protect the metal.
A larger torch must be used for larger amounts of metal-wear ultraviolet sheilding goggles.
Metal should be melted in small pieces.