Advice on dissimilar metals in lost wax casting?

[Shawn Pixley]

I am taking a lost wax casting class. Most of the other students are jewelers (not me). I am thinking of making fittings / pulls for a new jewelry cabinet for SWMBO. My idea is to cast an inner motif in silver and then cast that into an outer portion in phosphor bronze. Does any one have any practical advice for me?

I can smith and have done folded and machine metal work previously. I also have sand cast and cuttlefish cast before, so it is not totally my first rodeo.

[Dan Hintz]

Off of the top of my head, my advice would be to pay close attention to the melting point of each... order of pour/cast will make a huge difference here. Also, depending upon size, you may need to look at shrinkage percentages (though for something small like a pull, you'll likely be okay).

[Ryan Mooney]

I was surprised how close the melting points are (phosphor bronze 19200 liquidous vs silver at 1763). However phosphor bronze is solidus at 1750 so it actually gets a little soft at around where silver melts. That means one of two things, they'll either be easy to get to stick together or you'll have a tough time keeping the details distinct. I'm guessing you want to cast the bronze first based on that and maybe shoot for a slightly higher temp bronze.

No clue on the relative expansion ratios.

Sounds like a cool project anyway, would love to see/hear how it turns out.

[raul segura]

Sounds cleaver, I have not seen any work like this. 1.- You could cast all in bronze then ably soft silver over part needing ( plating ) to look like cast silver. 2.- Cast parts separately then silver solder parts together. 3.- If casting bronze over silver I would suggest heating the casting mold up before adding bronze so there is no extreme temperature difference during the pour. Lastly I would think you would need some sort of flux borax etc. to get dissimilar metal to join. I've cast navy bronze and aluminum, but nothing like this. Good Luck !