After following the previous three tutorials you should be ready to vent the mold to get the metal into those hard to reach places like reins of horses or the bayonets on rifles.
In the case of sprues surrounded by a frame you just cut a small vent from the problem area to this sprue. (Fig.1).
Use a sharp modeling knife and a HEATED mold to get an easier cut. Make as many such vents as required to allow the metal into the problem area.
(Fig.2) If the figure is not surrounded by a frame then always cut FROM the figure to the TOP of the mold. NEVER cut a vent to the bottom of the mold as the molten metal will only pour out through this.
When you have Vented the mold to your satisfaction you repeat the previous tutorials to cast the figure with safety as top priority as always.
(Fig.3) SUCCESS – The bayonet has filled this time.
However a slight shift has occurred because the two halves of the mould were at a different temperature. Try to keep both parts of mould the same temperatureto avoid this shift.
(Fig.4) Now to remove you beautiful new cast figure from the mould. Carefully BEND the mold when removing the figure and you reduce wear and tear on the mold (which makes casting in future more prone to errors) and damaging the figure (after all your effort it would be a shame to ruin it with a moments carelessness).
Tips to remember:
- Use a sharp knife and heat the mold when cutting vents.
- Cut from the problem area to top of mold or to surrounding sprue.
- Recast figure with attention to detail.
- Wait at least five minutes before opening mold.
- Keep both parts of mold same temperature.
- Bend the mold when removing figure or damage may occur.
