Archive for January 2011 | Monthly archive page
Since the lost wax process is complicated, potentially hazardous, and requires a lot of expensive tools to start with, I decided to do another tutorial. This one lets you start out with a bare minimum of equipment and still create stunning results.
To get started sand casting, you will need the following:Casting sand (available at www.riogrande.com ) A 2-part box (called the cope and drag) or a commercial sand casting frame baby powder or jewelers talc Pewter A hand held melting crucible A blowtorch with either MAPP gas or Propane a rolling pin or dowel A screen helps
First, you need to come up with some sort of 2-piece frame. I made mine from wood scraps and elmers wood glue. Notice the posts glued to it to assist with alignment. These are absolutely essential and must hold the frame from wobbling around at all. It is also a good idea to mark the sides of the frame with arrows to ensure the 2 parts realign exactly each time.
The part of the frame without the posts sticking up is places face up on a smooth surface. Clumps of casting sand are pressed into it like clay. (it is very much like clay). Press hard with your thumbs to ensure there are no voids and the clumps are pressed into one continuous slab.
When the frame-half is full, use a rolling pin or dowel to roll the surface smooth and flat.
Assemble the second half of the frame (the one with posts) onto the bottom you just filled with sand. Next, place the original model you want to copy on top of the sand, detail side up. When selecting you model, be sure it has no undercuts (such as a mushroom) or else the original will break the sand when you pull it out. Things like pins, brooches, belt buckles and pendants are ideal for this process. If the object has detail on both sides, simply press it into the sand halfway (but put powder on it first!). I opted to use a viking era flyfot ornament for this tutorial.
Next, sprinkle some baby powder (or jeweler’s talc, which seems like nothing but expensive baby powder to me) over the original and the sand. Using a very soft paint brush or a make-up brush, spread it around and make sure it isn’t piling up where it will interfere with the design. This is important and if you forget to add the powder the 2 parts of the mold will stick together.
Use a piece of screen and sift the sand on top of the prepared model. Once it is completely covered with a layer of sand, pack it down with you thumbs. Then fill the mold the rest of the way with sand and roll it smooth with the dowel just like before.
Now carefully open up your frame. A light tap on the sides helps loosen up the 2 halves. carefully remove your original model. You should be left with a prefect impression of the original.
In an area where it won’t be conspicuous on the finished piece, you have to cut a hole to pour the metal through. In my case, the flyfot has no detail on its backside, so dead center is best. On other designs, you might have to experiment. Just make sure that the hole you make is thick enough to allow the metal to fill the cavity before cooling off. I use a 1/4″ drill bit to poke my hole.
On the outside of the mold, the hole has to have a dimple carved to make pouring the molten metal easier. Just cut out a little funnel shaped dimple with a knife. Then carefully reassemble the frame making careful note of the alignment.
Now you are ready to pour. Get your safety glasses, your melting crucible, some pewter, and your blowtorch and head for a place where thousand degree spills wont be a disaster.
Heat the pewter with the blowtorch until its surface shines like a mirror and just the slightest hint that it is starting to turn red. It should roll like mercury at this point. If the metal is extremely dirty and has a lot of slag floating in it, skim that off with a piece of scrap metal. Then pour it into the cavity of the mold.
Wait a few minutes for it to cool, then pull the mold open.
After you break the piece out of the sand, you have to cut off the sprue where you poured the metal through. Then file the nub down and maybe polish the piece a little bit if need be.
And you’re done.