I will start by saying hello, as I signed up primarily to solve this major issue that I’m running across. I started making jewelry when I was fourteen (so a little over three years now) and am quite familiar with basic soldering, annealing, and forming concepts. I prioritize in chain weaving and clasp production, I make every finding, link etc. So I want to make my own wire/sheet and reuse scrap.
My issue runs into rolling out ingots into wire, as I roll it through it just cracks like dry clay on the second roll. I can snap a 7mm square ingot with my hands and it looks awful, I will attach a photo showing the break. I have made ingots out of scrap (very solder free) and new (alloyed by me) sterling silver. After becoming very frustrated I sent copper through which worked fine. I am going by various youtube videos by very reputable sources ( I won’t state names as I don’t know if Ganoksin permits that). I will now list off my exact…well… process.
Considerations-
I make sure silver scrap is clean/free of solder (scrap from wire sourced from riogrande)
I am using an oxy acetylene torch
Borax to flux
Preheating mold (Pepe tools open 4 sided)
Waiting till clean and very liquidus
Casting in a consistent motion (don’t mean to brag but I must say I’m quite good at it)
Am not sending ingot through rollers too tight
Annealing till cherry red and air cooling making sure not to move it
Everything in between
THOUGH IT COMES OUT VERY BLACK, WRINKLED AND BRITTLE
I have tried everything, you name it, I think I tried it. This batch of about 14 ozt of silver will be sent off to the refinery and started over. If anyone has any recommendations on this subject I would love to hear. If I have to cast in an argon shielded atmosphere I will quit tomorrow.
I will thank everyone in advance for your response, very much appreciated.
Try forging your ingots after they have cooled and you have removed any sharp edges and flashing. Start at one end using a cross peen or ball peen hammer. All you are trying to do is kind of dent the surfaces. Do all surfaces working in the same direction from one end to the other. Anneal again and then roll. You may also be getting the melt too hot. Try using a quieter flame or even a propane flame. Finally, start with a new crucible that you have coated with borax. Others may have additional ideas. Good luck…Rob
Milling out ingots is one of the most deceptively complicated things that we do. There’s a lot going on at once in the metal. Your metal shows signs of being pushed too hard, too fast though the mill or being substantially overheated during the pour. Also, I’m not a fan of open faced ingot molds. They tend to make bumpy and irregular ingots that require extra effort to mill out. That’s another possibility of what is leading to all of your problems. I prefer round or square two-piece ingot molds like one of these.
It’s also possible that it’s a combination factors. Like I said it’s complicated. It could even be hindered by your torch adjustment. You said are using an oxygen-acetelyne torch. You could be using an oxidizing flame (too much oxygen), instead of neutral flame. A flame with too much oxygen on molten silver will tend to make the metal be brittle.
This is a common thread here on Orchid. Here’s a similar question someone asked in June. Maybe that will be of some help.
I wish I could tell you exactly what to fix. I suppose if it was me, I’d get a two-piece ingot mold first. They come in a variety of prices and sizes.
@rmeixner Thank you! I do forge before rolling. I will have to try lowering my flame temp. Is there a sign that it is too hot? Also does overheating heat cause the discoloring I am having trouble with?
If it starts to boil and spit, it is overheated. Once it is fluid and you can stir it freely with a graphite rod, pour your melt into a mold that has been preheated and prepared with either burned off oil or coated with carbon from burned off rich gas. I agree that you should cast your ingots into an enclosed mold, not an open one. You can buy a convertible mold that will cast both rod and sheet. There is a lot in the archives about how to manage these molds. I sometimes cast rod in delft clay. That is another discussion. It just sounds like you are being a little too aggressive with your melts. You should probably recycle your scrap and start over…Rob
I was taught that with melting silver or gold with a torch, as soon as the top of the metal starts swirling in the crucible it’s the right temperature for pouring an ingot or for lost wax casting. It’s a fairly obvious transition if you’re looking for it.
I should also add that it’s important to agitate the crucible slightly or gently stir with a graphite rod to make sure there’s no unmelted chunks. Once you’ve verified that all the metal is melted and the metal has just started to swirl on top it’s time to pour.
The graphite rod also helps you find the steel spring that you might forget to remove from the clasp that you melted down. I know this from experience…Rob
I spent some time casting with your recommendation on not overheating. The cast comes out a lot cleaner, but still a tad brittle. Which brings up another question… once silver is overheated and impurities introduced I am assuming it is past no return, unless sent to a refiner? I am using scrap just to practice temp control, I will alloy new metal to roll.
Last time I was in contact with this term with respect to Silver, was someone that wanted Silver bars with perfect surface and dimensions. So it was suggested to mill them in a cnc router.
It’s always good to go over your scrap with a magnet. I keep one in the jar in which I collect my scrap and shake it once in a while. It could be anything from the size of a spring to small pieces of steel from your file…Rob
Milling as verb is one of those words in English that has multiple meanings. I took your comment to be a great reminder that communication through written words can be difficult and asking for clarity is often helpful. Thanks again for that!
I got curious and looked up the definition of milling as verb. I was surprised by how diverse of a word it is! Milling as a noun and a verb is one of those words in English that has many different meanings.
Here’s what Webster says. As crazy as it is these are just the meanings related to our field. There’s many more uses for milling. Such as milling flour and seeds or milling about.
silver crystallizes (large grain size) and become brittle if over heated or annealed too hot and too long… happened to me also… could be that cherry red is too hot, aircooling taking to long allowing for crystallization… try a lower temperature anneal, quick cooling in pickle… anneal each time it’s rolled until thinner and more pliant… oxyacetylene set to neutral flame to slightly reducing when melting for pour… excess 02 can cause some oxidation of copper in silver… anneal with propane air for lower temperature… Unless contaminated, no need to send back to refiner, just remelt and repour…
see my previous post… impurities will not be introduced by overheating if the original silver is clean… copper oxides do form with too much oxygen during melting but will be absorbed by the flux and the resulting melt be of slightly higher silver content… pouring into a closed mold cools the melt quickly, so crystallization is not the result of the pour… annealing temp was too high… you got better results with a lower temperature anneal… cool the annealed rod quickly for small grain size… drop into pickle rather than air cool… worth a try.
