Hi. Lately I’ve been playing with Argentium silver but I am a bit stuck at this point. I am using a crucible to melt it and I pour it into a charcoal block channel. However, even though small pieces turn out fine, larger pieces (10 grams) are experiencing a rather strange problem. The underside and the lower sides of the ingot crack when hammered or rolled. I tried to melt with less oxygen (oxy propane setup), melt directly into the charcoal block, stir it (using boric acid), nothing seems to fix it.
One thing, the top of the ingot looks smooth and fine but the underside is not that way (might be due to the charcoal not being smooth). Could this be the culprit?
I have open steel ingot molds and closed steel wire and rectangular ingot molds and have successfully used them to cast sterling, fine and 14 KY many times, but they are all a pain. My most successful and repeatable ingots are cast in either Delft clay or Petrobond. The only difference is the cost of the media and how much detail I need. You can cast standard sized ingots or odd shapes that give you a head start to the final shape of the stock that you are trying to create using Delft clay or Petrobond. This is just my way and certainly not the only way, but they work for me…Rob
Argentium is more fragile at certain points than regular sterling, it can crack or fracture with even the gentlest movements (literally, like nudging it over an inch on the charcoal block with your tweezers, ask me how I know…) so I wonder if that’s playing a role here. But I’ve only worked with it in soldering and fusing contexts, not casting, so there may be a whole other set of factors there I’m not aware of.
This makes sense. With the deft clay… the heat dissipates evenly when the metal is poured. Where as… with a charcoal brick…the heat would be much higher in areas, where the Argentium, is direct contact with the deepest point, of the channel, of the charcoal brick.
I want to take the time and let you know what fixed it eventually.
After trying to melt and remelt with tweaking this and that, nothing seemed to work, cracks every time even after as little as a few hammer punches. Spent some time reading througu this forum and others and I came up with what looks like a fix to it. There are actually two things, I’m not sure if one of them would have been enough, as I didn’t want to experiment more.
Possibly the channel in the charcoal block was too big so I made a new channel that the molten silver will fit into nicely and “fill” the hole, not just spread to the sides.
During smelting just before pouring it, I skimmed the boric acid that was there floating on the surface.
These two together and I could hammer the pieces and roll it with no crack at all. It was the same argentium ingot as the one that kept cracking and cracking so clearly these two steps helped a lot.
I hope “boric acid” was simply a slip of the pen on your part and you are actually sprinkling borax on the melt. Boric acid is not borax. They are two different chemicals and do different things. Borax is a flux. Boric acid is not.
Because Argentium is so fragile, the contractions that take place in a thick or large piece as it cools exert enough force to cause fractures. It makes sense that the cracks appeared on the metal that was close to the charcoal as it was cooler and fractured while the top was red hot.
It doesn’t take well to being worked in anything too thick or big. Reducing the thickness of the ingot was smart as it relieved the temperature variation.
Yes you do use boric acid with Argentium. In many instances you use no coating at all. I cast it a few times a week using only a very small amount of boric acid as a flux. Argentium when hot can be fragile and it is harder to see how hot it is in comparison to traditional sterling. Once cooled it is not fragile.
Franklin…who works with Argentium daily and has since it first arrived for use.