I've been playing around with lost wax casting for a little over a year and I'm having a lot of fun. I've scrimped and saved and purchased the equipment over time and have learned as much as I possibly can on my own from YouTube and Google searches.
I learn something new each time I go through the process and of course, every time I make a mold, it gets better and better. The tougher part is the cutting open of the mold. That's still going to be awhile before I'm really proficient. But, in the meantime, here are a few shots of the process I worked on this morning.
First, I gathered my supplies:
- Master model - in sterling silver with a brass sprue attachment.
- Castaldo Rubber - I use the vulcanized rubber method.
- Aluminum framing for the vulcanizer.
- Surgical blades to cut open the mold.
- Of course, the rubber strips from Castaldo.
My master model is a rifle with a scope that I cast from Lego weapons I collected to create my charms. Lego is known for their very accurate depiction of weapons and their highly accurate plastic models, so it was only natural to choose that as my starting point.
I attached my model to a sprue to give the mold an entry for the wax injection. This is the tough part - sometimes soldering brass to sterling silver can be a challenge, so I used E-6000 glue to attach the two parts instead.
Next, I used the aluminum frame as my template to trace the size on the rubber for cutting. Once the templates were traced on the rubber, I used my "kitchen" scissors to cut the shapes. My frame takes six (6) layers of rubber, so I cut out enough to fill my frame.
When the frame is packed to my liking, I place an aluminum sheet on both sides and place it into the vulcanizer to heat the rubber to form the mold. The heat used is only about 250 degrees F, so it's not too hot as to burn the rubber. It's just enough to "melt" it to create a tight fit around my metal model and the sprue.
Every two (2) minutes I use the handle on my vulcanizer to tighten the platens down on the aluminum frame to press the rubber into my model to ensure a very detailed mold. After the first 10-15 minutes of tightening every 2 minutes, I let the mold cure in the heated vulcanizer for about 40-45 minutes.
When the time is up, I remove the frame from the vulcanizer and set it atop my anvil to cool. The mold must be cooled to pull the aluminum framing off, so I leave it for about 15-20 minutes. Heating the rubber causes it to expand, so you see a bit of "run off" on the mold from the squeezing the platens produce. This is normal and is cut off using scissors or the scalpel.
After the rubber mold is cooled, it's time to cut the mold apart and remove the master model. This is the tricky part for me, but in time I'm sure I'll become an 'ole pro at it. Cutting the mold is also very dangerous to your fingers and other extremities! A scalpel blade is used and yes, it's just like a surgeon's blade, just not sanitized.
I used a protective glove on the hand that's not using the scalpel to save my fingers. It's a little big so the excess around the fingers kind of get in the way, but for now it works to save me from blood loss.
Finishing the mold is great, but the true test is the wax injection test. If I've cut it halfway decent, the wax injection will work beautifully and I'll have a mold to make multiple copies of my rifle for charms, cufflinks, pendants and whatever else I decide to make. You can see from the photo above, the mold worked and my cutting was very good this time around.
NOTE: Those of you who are pros at mold cutting will say this mold is terrible, but the point is I can get a clean wax model and it serves its purpose.
Whew! That was fun... Now on to make the master models for the twelve (12) other Lego weapons in my arsenal - yes, pun intended!