When I melt silver and gold a surface film dances on top of the melted ball. What is it and how do I prevent or remove it?
I can’t answer your question, but I think that it is pretty normal. That is the point where the melted metal is interacting with the O2 in the air around it. I have noticed that it is less likely to happen when I melt a small quantity of silver on charcoal than on another type of heat resistant material. Charcoal produces a natural barrier to O2. Someone with more knowledge than I will have to actually answer your question. I hope they do. Thanks for asking it…Rob
I’m with Rob! I hope that one of our engineers or material scientists in the forum can answer your question.
But like Rob said, when silver and gold melt the metal will swirl. It’s a normal part of the melting process. In lost wax casting for instance, when silver and gold start to swirl is how you can visually tell that that the metal is at proper melting temperature for casting.
Why it happens and what about silver & gold and environmental circumstances cause it though I don’t know.
One thing that I do know is that if you go past the proper melting temperature and get the metal too hot, you can essentially burn it and wreck it. I often compare melting silver and gold to melting chocolate. Chocolate has a very limited optimum melting temperature. If you go past that temperature, it wrecks the chocolate. The same is true for silver and gold.
I’ve got a question for you. What’s your goal in melting silver and gold? Are you trying to make perfect silver and gold balls? Are you casting ingots or doing lost wax casting? Each of those tasks potentially have different answers.
Jeff
I’m just melting down some small pieces into balls.
Like Jeff says, you will see some swirling and sometimes what looks like scale on the top. I have no idea what it is. Time to do with them what you plan on doing as you can over heat the metal. If you are trying to make little balls, and also have a charcoal block, carve a ball shaped cavity into the charcoal and melt your metal there. Apply the flame straight down and when the ball starts to form, pull the flame up slowly away from the ball. The force of the flame can distort the shape of the melted metal as it cools. There are more sophisticated ways to make balls that include starting in a cavity and then letting the melted metal roll down an inclined charcoal pad until it solidifies. You can also let the melted metal drop into a container or water. This will form a lot of different interesting shapes depending on the height you drop it from and the depth and temperature of the water. The cool thing is that, if you don’t like what you get, you can redo it. This is a deep rabbit hole that you can go down into for days. Have fun…Rob
Great advice Rob! I was going to say the same things.
One thing I’ll add is that sometimes the most effective way to get perfect balls is to use casting grain. Not as much fun for sure, but if you have casting grain sitting around, it’s a quick solution.
Jeff
More often than not, I want to create little silver balls that are the same size. For me, the best way to do this is to use jump rings and keep a record of the size (gauge and diameter) and the number needed to create the desired size ball…Rob
From Jewlery Making and Design, Cirino and Rose, first published 1918:
“…we can apply [to a pendant] small shot varying in size as shown in fig. 24. These shot are made by taking round wire (No.20 gauge) and cutting it in lengths to give the required size. These small pieces of wire are placed on the charcoal block and, after being coated with borax are heated to the melting point. This causes them to roll up into shot.” Emphasis added.
This is nearly what Rob has suggested. If you make depressions in the block for each jump ring (which is just an easy way of measuring out the length...and you can use smaller gauge wire, too, as needed) they will not roll off the block. If you use the borax or other barrier flux, you can pickle as needed and then they are ready to solder onto whatever. These shot may have a very slight flat on the bottom, but that is an advantage if you are going to solder them onto something. Am I belaboring the obvious here?
One could also look back on this forum for threads related to making granules for granulation. It's done similarly except that the jump rings are placed in granulated charcoal and melted in a kiln, then sieved out of the powdered charcoal...which you can make by sanding or filing barbeque charcoal. I don't remember the exact temp, but you can find it in the discussion or in some jewelry texts. Consult your local library or openlibrary.org.
-royjohn
Apologies for the lousy formatting! I can’t seem to fix it by editing.
-royjohn
I’m not making granulation balls. What I meant was I get some scraps and I melt some in a concavity in a charcoal block. It makes a ball of molten metal. I roll it flat to use for some other purpose -sorry I should have been clearer. After I have pickled it it is still not shiny but a bit rough as that film is still there. Should I sand it off? Is this normal or am I doing something wrong?
It won’t be shiny after you pickle it. If you are lucky, it will be a snowy white depending on how strong the pickle is. If it isn’t snowy white, boil it in a strong pickle. This will remove any glassy flux deposits. Then you can grind, sand, polish or just burnish it depending on the finish that you want when you incorporate it into some new piece. What you are seeing to start with is pretty normal depending on how it is pickled. There is a lot going on here. A ball of metal made this way is like a rough casting. You need to work on the surface to get it to where you want it. If all you have are little balls, you can press them in a dapping die to refine the surface and make it curved. It is my personal preference to grind and sand after pickling to remove any fire scale. Then polish with tripoli and rouge to make sure that you have a blemish free high finish. At this point you can leave it alone, texture, patina or any combination that serves your design needs. You seem to be looking for absolutes. There are very few in what we do. Good luck and have fun…Rob
First of all, no not looking for absolutes. I asked a question to find out whether I was doing something incorrectly eg should I add a sprinkle of borax or is this film on the molten metal that appears when it melts perfectly normal.
Thank you
Hi,
I have experienced what you are talking about, but not often…so I would not say it is what you should normally expect…
(how much silver are you melting? is it clean sheet and wire?)
i think i would
- pickle, rinse, dry
- sand off the rough surface
- and then forge with a hammer (usually to about 50% of original thickness…(i am not sure what you are starting with or what thickness you want to result in)
- then anneal
- then roll down further if needed…
i think i would definitely remove “film” before forging or rolling…
hope that helps…
julie
Thank you Julie that’s what I really wanted to know.
Liz
What Julie describes is standard treatment for an ingot that you have poured from scrap. Which is apparently what you really want to do rather than do make small metal balls or beads. I am glad that you got your question answered. These discussions often go in different directions than the OP planned. A lot of information is shared and people who may not be comfortable asking a question have gotten an answer as a result. You might consider collecting your scrape until you have enough to melt it in a crucible and pour it into an ingot mold. This way you can make sure that it is well mixed, you have been able to remove trash and impurities with a graphite rod and it is hot enough to pour without getting it too hot to drive off the zinc that is part of the alloy. Make sure that your mold is oiled and hot enough for the oil to stop smoking and then pour. Once you have an ingot, treat it as Julie suggested that you treat the small pieces. Good luck…Rob
Casting ingots and milling it out into usable metal stock can be a difficult and frustrating process. There are many variables.
To clarify, you’re not using an ingot mold, you’re melting scrap metal open faced onto a charcoal block. That path works, but it tends to make bumpy ingots that can be harder to hammer and mill out with a rolling mill.
That said I have a friend who makes what he calls bread loaf ingots. He melts a small blob of scrap silver or gold on a charcoal block and while it is still red hot and malleable, he lightly squishes it with tweezers to make a bread loaf shaped piece of metal that he can roll out in his rolling mill. I’ve watched him do it and he makes it look really easy. I’ve never seen any one else do this. I’ve tried his technique with marginal success, but I’m sure if I kept on practicing I’d get it. I always use two part steel ingot molds for making ingots to mill out. That’s what works best for me.
Here’s a recent thread with a slightly similar question that might have some helpful info for you.
Best of luck and keep asking questions!!
Jeff
Hi,
also…regarding sprinkling borax, here is my generalized understanding (not instructions really)…
so…borax is used to coat crucibles…then while the metal is melted some borax is sprinkled on…the crucible is “swirled” around and the borax in the melt, and the borax coating the crucible, attracts/ sticks to/ picks up” impurities, which sticks to the borax on the crucible…a graphite stirring rod can also be used to stir the melt and attract/ pick up borax laden impurity sludge…
i was thinking that if you are melting small raisin or grape sized melts, that borax might not be easily applied…?…i may be incorrect…
perhaps the “scale” on the surface is copper oxides…or…?
julie
As a test, I had a large piece of scrap sterling silver that I coated with flux and melted in a charcoal depression. Just before the metal was fully melted, there was a flash of what looked like charcoal dust moving around the surface of the melt that then disappeared. I pickled then rinsed the melt and put it back onto my scrap pile. As an aside, I also discovered that I must have introduced some carbon steel into my pickle because the pickled piece of silver was completely copper plated. Now I have to replace my pickle…Rob
Hi W melts are not usually as small as that. More like 15-30gms
Rob that’s interesting- I didn’t think of coating it with flux.
Sorry your pickle got contaminated.
Thanks!