• Wool Ink Paint

Of Silver and Wool - Lost Wax Casting Process

The quick answer to how I create our sterling silver jewelry pieces, is that I carve each piece out of wax, then create a mold around the wax piece, bake the mold in a kiln to remove the wax and harden the mold, then pour molten silver into the cavity left in the mold by the wax carving, and finally break the mold to retrieve the piece.  If you’d like a more detailed explanation, please see below.

Photo 1 - wax carving of sterling silver mountain pendant

Photo 2 - Our lost wax casting work shop

Photo 3 - Sprue tree of turtle and celtic knot that has just been cast

Often before I begin designing a new piece, I’ll have an idea in my mind about something I’d like to make.  From here I usually sit down with my sketch book and start working out what the piece will actually look like.  Once I have a clear idea, I begin carving it in wax.  I use many different tools but, mostly dental tools, files, jewelry saws, and sandpaper.  When the wax model is finished, I attach it to a wax sprue, and weigh it so I may calculate the quantity of silver needed for the cast.  A sprue is a structure like a tree, that allows one or more pieces to be attached together, similar to the branches of a tree, and then the sprue/tree is attached to a sprue base.  The sprue base is a rubber disc that fits very snuggly to the bottom of steel flask (cylinder).  After I have attached the piece to the base and fitted it to the steel flask, I mix up the mold material which is called investment.  Investment is a white powder that contains cristobalite, quartz, and gypsum and when mixed with water creates a slurry that can be poured over the wax piece inside the steel flask.  The slurry dries and hardens in a couple hours, and the flask can then be put in the kiln for 8 hours, where it bakes at a gradually increasing temperature, that peaks at 1,350 degrees F.  When the baking of the flask is done, the wax carving has burned out of the mold completely, and has left a cavity in the mold, that I can fill with metal.  So the next step is to heat the silver to 1,800 degrees F, remove the flask from the kiln (still at 1,300 degrees F), and pour the silver into the mold inside the steel flask.  After the pour, I place the flask in a bucket of water to quench it, this process causes the mold inside the flask to break apart, making the newly cast silver piece accessible.  Then I pickle the new piece in an acid bath to remove the oxidation caused by the casting process and cut the piece away from it’s sprue.  I’m then able to grind and polish the piece, and finally attach a chain and findings so it can be worn as a necklace. 

North's jewerly work bench