Back to Ganoksin | FAQ | Contact

Melting bronze casting grain with a map torch

I would be so thankful if somebody could tell me what I’m doing wrong! I’ve watched countless videos in preparation for this and am using a map torch which gets hotter than propane so this should work. I’ve tried different flame sizes, changing distances. I got the bronze granules to slump slightly at first, but then they stopped and never liquified and they stayed in ball form even though I kept the flame on it for almost half an hour. I tried adding a pinch of Matt’s casting flux once and a while, tried heating while the crucible sits further into my brick oven I made. I bought the torch a professional jewelry designer told me to buy. I feel like I’m not using too much granules. Almost a tablespoon I think. It made a nasty mess at the end. Not sure if this is salvageable. Also tried prepping the crucible with Rio’s suggested casting flux which is another story.

Oh it’s Rio’s Ancient Bronze whith is “90 copper and some tin”.

Thanks,
Daniel

1 Like

In simple terms you have a flame that is hot enough but not enough heat. Confusing right J

The problem is while your flame is hot enough (degrees C or F), you are not generating enough heat (BTU or Joules in metric) to bring the mass of metal up to the melting point. You can address this in many ways, different torch, multiple torches or keep the heat that you generate from being drawn off by convection or conduction. The crucible and fire bricks are a good start, but there is no way a plumbers torch is going to produce enough BTU to melt the metal in the crucible, you might need 2 or 3 of that kind of torch going at the same time to beat the heat losses from your setup.

3 Likes

Even though his map gas torch flame flame is advertised to be 3750 degrees? (Hotter than propane.)
Others are using map gas torches, no extra equipment or tips, oxygen tanks, and just one torch, to melt 24k gold which has an even higher melting temp than bronze. I wonder why the guy told me to buy this exact setup, unless he was pranking me!

Am I correct that 24k Gold melts around 1945 F?
And Bronze at around 1740F ?

The fact that a torch burns at a specific temperature does not mean that enough heat energy is transferred to the crucible to heat the metal in the crucible to that temperature. I believe that this is your problem. Good luck…Rob

1 Like

I came across this video by Craig Dabler where he shows how to use the Bernzomatic MAPP Pro cannister attached to a torch to melt silver. Since he is actually melting the metal in real time I assume it works. You might watch the video and see if you are doing anything differently that would explain the problem. https://www.youtube.com/watch?v=eFd1huCQL-c

Also, I’m under the impression (how’s that for scientific?) that copper is harder to melt than silver…as in needs more heat, bigger torch. Have you tried melting some silver with your setup?

1 Like

Sterling silver melts at a lower temperature than copper. One online source says 1640 F vs 1983 F. That is around a 20% difference. Practically speaking, in my shop with my propane and O2 torch, I know that it is a lot easier to melt Sterling silver than it is to melt and equal amount of copper, all other conditions being the same…Rob

2 Likes

I melt and cast Rio’s Ancient Bronze at 1070 C (1958 F).

1 Like

I actually have not tried silver yet. I just assumed bronze would works since the person that told me to get this used it to melt gold. Thank you! I’m going to watch that video.

Ok thanks. I noticed the melting temps are different depending on what source I’m looking at!

Many beginners are unaware of the “zones” of a flame and try melt with the inner blue cone of the flame when in fact that’s the coolest part of the flame. As a general rule I don’t touch the metal with the blue cone.

MAPP gas should melt the bronze! Are you pre heating the crucible?

Do not let your crucible rest on the bricks when you apply your heat. The bricks might not be allowing your metal to get hot enough to melt.

You need Oxygen, not just air. Bronze melts at a higher temperature and that’s a good amount you are attempting to melt. In my experience of casting (which is a lot of teaching and casting various metals over many years), I think you’ll be hard pressed to build up enough BTUs without amplified oxygen. A bellows system for a crucible could be devised, but most opt for adding an oxygen tank to their set up.

Ruthanne

1 Like