What kind of metal/alloy could this be

[Maurice]

Hello everyone,

I recently opened up a handle of an unmarked silver knife and found a soft heavy metal beneath a thick layer of silver instead of cement. might be a pure metal or an alloy. It is not magnetic in the least when holding a neodymium magnet close to the metal. It is easy to cut and can be manipulated by pliers or cut with some scissors. The cut edge is shiny and is not tarnished after a couple of days in the open air. At least no visible oxidation is forming.

I put a tiny piece in cold 30% HCl to see if it would react. At first the reaction was immediate, bubbles forming right away, but not so vigorous as Al or zink would. The solution is colorless.

The next day the bubbling is reduced a lot, but still bits and pieces are dissolving. Also There seems to be a black layer being formed on the remaining piece. The solution is still colorless

The second dag the bubbling has reduced some more and the black layer is now thick and covering the whole piece now. Besides that there is a little bit white precipitate that also has formed. It isn't fluffy, looks more course like fine sand then a very fine powder. The solution is still colorless.

observations so far:
- The black layer seems to be pacifying the metal beneath it and preventing the remaining metal to come in contact with the acid.
- Considering the reaction is much less reactive then Al The metal must contain at least one or more metals that are less reactive then Al or even Zink
- The solution stays colorless up till now
- Some white precipitate has formed at the bottom

Does anyone have an idea what metals or alloy might be used as filler for the knife handle instead of cement. Any idea what metal/alloy would pacify with a black layer in 30% HCl. And what might the white precipitate be that formed in the solution.

 

[g_axelsson]

Sounds like tin, i.e. pewter. The black layer is probably antimony, a contamination common in tin.

Try a drop on a filter paper and put a drop of weak gold chloride on it. If it goes black and purple you have made a lifetime supply of stannous.

Göran

 

[kurtak]

Its lead - before lead became a big concern as a toxic metal it was not uncommon for "some" companies to use lead as the fill on knife handle's --- & most commonly on the knife handles of silver "plated" silver sets but not on 925 (sterling) sets

I recently opened up a handle of an unmarked silver knife and found a soft heavy metal beneath a thick layer of silver instead of cement

Per the underlined - this also tells me that the knife handles are more likely silver plated rather then 925 silver

Three things that tell you knife handles from silver sets are silver plated & NOT 925 silver

1) - they are unmarked

2) - the shell is much thicker then the shell of 925 silver (2 -3 times thicker)

3) - the shell is filled with lead rather then filled with a resin (commonly found with sets made before the 1960s

Kurt

 

[kurtak]

Sounds like tin, i.e. pewter. The black layer is probably antimony, a contamination common in tin.

Try a drop on a filter paper and put a drop of weak gold chloride on it. If it goes black and purple you have made a lifetime supply of stannous.

Göran

The HCL is pasivating the lead --- no tin

Kurt

 

[canedane]

My guess, it is a Zink alloy. Try to melt it with some Sn and see what melt first. If i am right the Sn will melt first. Try the density and you will know if it are Lead.
Henrik

 

[Maurice]

I put the small beaker on a hot plate en set it to low-medium heat.

The piece that is plated dark grey/black seems to be a little smaller. The while course powder is now turned into white flakes and increased in numbers.

I'll do a few tests described in the responses and try some boiling water to see if the while flakes will desolve indicating it would be lead indeed.

The Thickness of the silver alloy on top of the unknown metal is at least 1 mm thick if not 2 mm. It is tarnisched as silver would tarnish. So I assume that it is a silver alloy, .800 or a little more.

I'll make a few images tomorrow so you have a better picture. I could do a volume measurement and calculate it's density see where I end up.

Thanks for the answers so far

 

[kurtak]

I recently opened up a handle of an unmarked silver knife

What we know --- ALL silver smiths that make silver flatware sets hallmark ALL pieces in the set including the knife handles - the common hallmarks are sterling (the actual word) or 925 or 800 --- on knife handles the hallmark is normally found on the very edge of the handle where the knife blade goes into the handle - the hallmark will be VERY small & hard to see/find - but it will be there

If there is no hallmark it is NOT silver but silver "plated"

The Thickness of the silver alloy on top of the unknown metal is at least 1 mm thick if not 2 mm

Per the underlined - the shell on a (real silver) knife handle will NEVER be that thick - the shell on a real silver knife handle is normally about the thickness of 3 or 4 pieces of paper (which is less then a millimeter) in other words "at most" a real silver knife handle shell will be around 1/2 mm thick & they can be thinner then that

And - that is one of the reasons why real silver knife handles are NEVER filled with another metal --- the temp of the molten metal being poured into the knife handle would cause the VERY thin shell of the handle to warp &/or deform

It is tarnisched as silver would tarnish

That because the "base metal" of most silver "plated" flatware is made of nickel brass which is an alloy of copper & nickel which is a silver/white metal due to the nickel "bleaching" the copper to a white metal - it is also often call "nickel silver" because of its silver/white color but there is NO silver in it

Nickle brass is "a bit" more gray then real silver - so if the silver plating has wore off it will "appear to look like tarnished silver

Everything you have said tells me its not real silver but silver plated

1) no hallmark --- more then likely not silver

2) more then 1mm "if not 2 mm" thick --- most likely not silver

3) filled with metal (instead of filled with a resin) --- it's not silver - (or at least it would be the first I have ever seen)

My answer is based on the fact that I have processed knife handles by the 5 gallon bucket full

That said - without actually seeing what you have I could be wrong --- but I doubt it - based on your description I think you will find they are silver plated handles & not real silver handles

Kurt

 

[Shark]

My findings have been the same as Kurt's. Depending on how you want to run silver plate you may not need to remove the blade. In an H20 cell I don't take the blades off. If I put them away for future processing I heat them gently and bang it against a vise until the blade pops out. Don't heat them fast, or over heat them, as they can spit a blade dangerously fast at times.

 

[grainsofgold]

We remove sterling knife blades often. Most are a pink resin that comes off easily. The others have a metal filler. Here’s two xrf readings from two samples of the metal filler.

Notice mostly lead , some Tin and Antimony.

Some have suggested heating and dripping off as much of this as possible then do a hard boil in HCL to remove the remainder from the Sterling. i have not tried this yet.
Has anyone ?

 

[jphayesjr]

Read Hoke.

 

[kurtak]

then do a hard boil in HCL to remove the remainder from the Sterling. i have not tried this yet.
Has anyone

With the lead being that high you are better served using HOT nitric instead of HCl

Kurt

 

[grainsofgold]

PROCEDURE WHEN TIN AND LEAD ARE PRESENT—ACID METHOD For your first refining of rolled, filled, or plated scrap, take clean stuff such as old spectacle frames, or old jewelry or collar buttons. Sometimes the thin outer layer of gold is firm enough to keep the acids from reaching the base metal core; therefore roll this scrap out thin, cut up the pieces and twist them to keep them from lying flat in the acid. In many cases the gold layer is so thin that this
precaution is not necessary.
If there are visible lumps of soft solder, cover the articles with
full strength hydrochloric acid, and heat to boiling until the solder loosens and can be scraped off. Then pour off the acid and throw it away, and wash the metal thoroughly to get rid of all traces of this acid. Wash till the washings have no more sour taste, or fail to turn blue litmus paper red. (See Chapter IX.)
Next, treat the metal with nitric acid and a little water, as usual. Since low grade scrap is mostly base metal, you will need much

72 REFINING PRECIOUS METAL WASTES
more acid than in Chapters V and VI, and there is much more chance that it will boil over, so add the acid slowly. This dissolves all the copper, silver, brass, zinc, iron, cadmium, and nickel, that the acid can reach. Tin is converted to the gelatinous tin paste. Lead turns into the scantily soluble lead nitrate; add a little more

 

[BlackLabel]

Why would someone dissolve the filler?
Peel off the silver dump the remaining filler.