Question about making bronze.

[Storm W]

I am making some bronze for bolsters. It seems like I'm adding more tin than is needed. The first melt was pretty liquid but as I remelted it it seems like I was getting more and more really thick material on the top. I was wondering if maybe I am not giving it enough time to heat all the way back up, if the tin is vaporizing out if it or if I need more flux on top or something else. Does anyone have any ideas?

I think I may have come up with a fast way of fitting bolsters. I'm casting basically a C channel and I figure that I can real quickly just grind the flanges down to the thickness of the tang stock and then weld a cap on it. That should shrink it to a really tight fit. I can just move material around with a Tig. So long as it's the same batch it should color match.

 

[Ken H>]

I'm not at all familiar with making bronze, but when casting bullets with a lead/tin alloy the tin will float to the top forming a "slag" looking layer floating on top of lead. This requires fluxing to get the tin back into solution with the lead. Flux is usually beeswax or something similar - just a 1/4" chunk of beeswax stirred in the mix will usually cause the tin to go back into solution leaving a nice shiny surface. Of course with lead/tin alloy we're talking about 800°F at max, usually around 725°F or so. Not sure what's going to happen up at almost 2000°F or so for melting copper.

Since the boiling point of tin in around 4100°F I wouldn't think the tin is vaporizing out. Since you mention flux, what are you using for flux? Maybe get it up around 2100°F, stir good to get tin back in solution and pour while in solution?

Good luck and let us know how it turns out.

 

[Stacy E. Apelt - Bladesmith]

90/10 copper/tin. Cast at 2000F. Stir with a carbon rod.
I just use normal casting flux, which is borax and a little salt peter.

 

[Storm W]

I had the oven on at 2100. I was using borax for flux. I didn't know about the salt peter. I will mix in some of that wall. What kind of ratio do you use?

This was my first time using casting sand. It seems like it dries out. Is there something that I can do to bring it back to where I can use the same same again.

What do you think about my idea of Tig welding the two halves together? Seems like an idea to really speed things up. Without a mill I am slow fitting bolsters.

 

[Mecha]

What do you think about my idea of Tig welding the two halves together? Seems like an idea to really speed things up. Without a mill I am slow fitting bolsters.

I sometimes do something similar to make sword handguards out of titanium plate.

Since the tangs on my swords are not rectangular in section and are more like an irregularly curved wedge, filing a tight-fitting guard slot with needle files is very tedious, especially in titanium alloy. So sometimes I'll cut a slot with a bandsaw on the bottom of the guard, as wide as the widest part of the tang (the spine side), then heat n' beat the sides of the guard piece to close the gap, forming a curved hole similar to the tang's sectional shape. The part on the bottom of the guard is then cleaned and welded, leaving just minor needle filing to fit. This is a much faster way for me to get this done than drilling a hole and filing, especially in thicker plate.

I also like the dissimilar pattern it makes. Here's an example of a thin one on a machete:

 

[Stacy E. Apelt - Bladesmith]

The saltpeter (potassium nitrate) seems to help with clearing the dross off the top. I don't use any exact ratio, but about 1 part saltpeter to 9 parts borax seems right. Another flux mix has a little powdered charcoal added as well.

 

[Storm W]

I have

The saltpeter (potassium nitrate) seems to help with clearing the dross off the top. I don't use any exact ratio, but about 1 part saltpeter to 9 parts borax seems right. Another flux mix has a little powdered charcoal added as well.

I have both of them. Saltpeter is one of those things that's cool to have around. I used it to cure a roast and it came out really nice. Then there are stumps to burn out and who knows it could be fun to try making black powder. I always wanted to try it. I don't live far from PA and they have a flintlock deer season. Someday it would be fun to cook a meal where I made every tool to prepare it from start to finish.

What are your thoughts about other types of bronze bronze. I sometimes toss in a chopped up aluminum TIG rod and sometimes some lead. I have used scrap copper so far but tin is expensive. I love the look of bronze. I want to get good at making it. I have a friend who is a jeweler and with gold so expensive she is looking for other options. I enjoy making a few things for my wife and learning from her. She bought some cheap rollers and I'm trying to get her something interesting that she can run through her rollers. My thicker pieces seem nice and solid but the thinner pieces are brittle and course grained. Is there a way to add steel easily to the mix? I see it in commercial alloys. Also silicone bronze. I know JT was doing it. I want to play with different colors and I need to get the different chemicals for patinas. Do you have any recommendations for ones that are easier to work with or chemicals that will be the most interesting to work with.