What happens if silver gets too hot?

I guess turkey season is coming soon, but you'll have to wait for the full moon for the were-turkeys. :)

cheers T.Alan

Yep it will oxidize and become porus. You should melt it only until it become fluid and takes on the appearence of liquid mercury. Add some borax as a cover flux to keep the oxygen from the molten silver. Stir with a carbon rod and the crap(dros) will float on top in the borax so you can remove it befor casting or pouring your silver

Melt the Silver under a flux. When cold it reacts with oxygen, but then hot it really reacts rapidly. Any chlorine in the mix and it will steal the silver.

Melt from below and have a flux surface. If possible pour from below and let the flux/dross float down to the bottom...

Martin Martin H. Eastburn @ home at Lions' Lair with our computer lionslair at consolidated dot net TSRA, Life; NRA LOH & Endowment Member, Golden Eagle, Patriot"s Medal. NRA Second Amendment Task Force Charter Founder IHMSA and NRA Metallic Silhouette maker & member.

Ben wrote:

Jewlers melt from the top, and without it being "under" flux all the time. Just a light coating of flux is all that it needs, and a neutral flame.

"the bubbling" may have been due to the borax he put in, and the crucible being brand new, from another of his questions.

Nice if you can do it. I expect the next questions will involve cent. casting machines, which effectively do pour from the bottom, but are heated from the top.

Only if alloyed. Pure silver isn't prone to oxidation, although it has the capacity to absorb 9 times its volume is oxygen, which it expels as it solidifies. If working with alloyed silver, the copper does oxidize, yielding porous castings. The metal tends to have a burned copper look about itself in that condition, and doesn't clean well in a pickle.

Add some

In the case of melting pure, all that is required is for the crucible to have a film of clean borax melted and well distributed. As there should be no oxides for the borax to absorb, it acts as a lubricant you get a clean pour, leaving nothing behind. It's very desirable to not have an excess of borax, so it doesn't pour off with the silver.

Harold

Not true. Silver doesn't react with oxygen easily, not at any temperature. Silver is difficult to oxidize, as I've already mentioned. It sulfates, which is the brown familiar color we've all seen on silver that needs to be polished. It does absorb oxygen when molten, but readily gives it up when solidifying. The only effect is that when it expels the oxygen as the silver solidifies, it tends to leave tiny spires on the surface of the silver. Alloyed silver isn't prone to this reaction, the alloy reacts with the oxygen, so the silver doesn't absorb it.

A flux cover isn't a good idea, but a covering of charcoal is very good---it reacts with free oxygen and prevents the silver from absorbing it.

Yep-----it's a well known process of refining large volumes of gold to a high degree of purity---- (It's known as the Miller chlorine process in the refining world).

Pouring from below is a good idea always, but I'd avoid a flux cover for many reasons, one of which is flux is exceedingly hard on crucible life. Only a thin film for lubrication is recommended.

Harold

To expand on this, you can tell if your silver is alloyed with copper, by heating it and letting it cool in air, with no flux on it, if the surface turns black, it has copper. Sterling will fairly much come out of an investment black, fine will pretty much come out silver (a matte gray)

Jim

jk

Thanks Jim/all, this makes sense. The silver did stay silver but all I did was melt and pour in a bucket of water. No surface tarnish at all, very bright. I haven't actually cast yet and that's when I expect the grayish finish that'll have to be pickled and then buffed off. One step at a time though still tweaking my furnace at the moment. Found some good castable refractory and ceramic wool locally. Let it set 24 hours then baked in my oven all day starting at 150 and bumping it by 50 degrees every couple hours until I hit 500. Not a crack to be seen even after bringing it to working temp in the fire...but my design was flawed so I'm waiting on my re-cast to set.

One thing about this hobby I'm learning each seemingly simple step seems to turn in to a whole project in itself. And there's so damn much to learn! Fun though. Just looking forward to my first successful cast at this point.

Have a good one.

- Ben

Right - but Jewelers are experts by the time they are doing it.

It is obvious that the current user isn't expert and doesn't know a neutral flame from a hot one.

If he put borax in it - it would melt and surface. It is the flux. It may not be the best and it is likely ok. Silver is touchy.

Martin

Martin H. Eastburn @ home at Lions' Lair with our computer lionslair at consolidated dot net TSRA, Life; NRA LOH & Endowment Member, Golden Eagle, Patriot"s Medal. NRA Second Amendment Task Force Charter Founder IHMSA and NRA Metallic Silhouette maker & member.

jk wrote:

| >Melt from below and have a flux surface. If possible pour from below | >and let the flux/dross float down to the bottom... | Nice if you can do it. I expect the next questions will involve cent. | casting machines, which effectively do pour from the bottom, but are | heated from the top. | >

| >Martin | >Martin H. Eastburn | >@ home at Lions' Lair with our computer lionslair at consolidated dot net | >TSRA, Life; NRA LOH & Endowment Member, Golden Eagle, Patriot"s Medal. | >NRA Second Amendment Task Force Charter Founder | >IHMSA and NRA Metallic Silhouette maker & member. | >

| >

| >

| >

| >Ben wrote: | >> Another newbie question. Yesterday to get a feel for what it's like to do | >> some very basic work with molten metal, I melted a silver bar and poured in | >> a bucket of water to create shot. A couple things I hadn't anticipated | >> happened. One was that the silver bubbled where the flame touched it. I | >> read it might "roll" but nothing about what appeared to be surface of the | >> button actually boiling. Is this normal? Can you oxidize silver by getting | >> it too hot like what happens to an aluminum can in a camp fire? | >>

| >> I'm a beginner and have never even seen anyone do this, just going off what | >> I've read here and in a book. Trying to minimize loss of material through | >> my learning process. | >>

| >> Thanks all, this group has been an AWESOME resource. | >>

| >> - Ben | >>

| >>

| >

If you increase the application of heat to a melting silver it will reach a point where it will boil just like any liquid. Any more heat at that point will cause a violent boiling action and possible ejection/explosion of melted matters just like what you observe with the escaping magma from a volcano. I don't see any reason why you would want to keep on increasing the heat on an already melted silver anyway. Jeweler's practice is to increase the application of heat on the silver with flux until it totally melts and then MAINTAIN the heat at the melting point in order to pour the fluid silver into a mold or whatever.

Harold, et al,

Might I presume this thread is about melting silver with a torch ?

Bob Swinney

Yup, I used MAPP/Oxy. First timer here and wanted an explanation of what I was seeing. Getting better with practice it seems the trick is hot enough so it doesn't solidify during the pur but not too hot either. A lot better now with timing and coodinating the crucblie lift with right hand while torch still heating with left. So far so good, long ways to go thouhg.

- Ben

Actually it is one of the first things I learned, and was certainly no expert. jk

messagenews:1172027312 snipped-for-privacy@sp6iad.superfeed.net...

I noticed that the antimony man

rowell ladles, which have a tube welded or cast into one side, open at the top edge and open down near the bottom on the inside. This allows the user to pour from the bottom.

Are there crucibles made the same way? Or is that a bad idea, would metal spurt out the tube if gas is evolved in the metal?

Yes------they're named bottom pouring crucibles----and work accordingly. I've used them in a size 8. There's no reason for gasses to cause an eruption of metal----the crucible is open to atmosphere and is free to outgas as required. The spout is heated while the metal is melting, so it has little reason to create any gasses when it sees molten metal.

Harold