Leica LTM Woods metal or Wismut

Leica M39 screw mount bodies/lenses
Dear Michael,

The late Colin Glanfield worked this one out 20 or 30 years ago, but neither he (nor I) knew about Wismuth; we thought it was just Woods metal. Part of the trick, of course, is an alloy with a very low melting point; Woods metal, as I recall, is liquid in boiling water. Thanks for the link and for vastly more information than was hitherto available.

Cheers,

R.
 
Roger,

I've been pondering Wizmuth and think it may transnslate into Bizmuth which, if I remember correctly is somewhere out on the fringe of the periodic table and a name I came across when involved in a jewellery project involving inlays years ago. Don't really want to go much further in case I am barking up the wrong tree...lets see what others have to say.

Michael
 
A (or the) major component in all the low-melting-point alloys of which I am aware is bismuth, but I don't know of any that contain silver. Wismuth is, it seems, merely the German for bismuth.

Cheers,

R.
 
Bismuth is certainly a major constituent of low melting alloys. Just for reference, Wood's metal is:

Bismuth 50%
Cadmium 12.5%
Lead 25%
Tin 12.5%

(I assume these percentages are by weight and not mole fraction.) It has a melting point of 73 to 77 °C. The melting points of the individual metals are:

Bismuth 271 °C
Cadmium 320.9 °C
Lead 327.4 °C
Tin 231.9 °C

As far as I'm aware, Wood's metal and my family surname have no connection, although I am a chemist...
 
The link mentions the use of Nitro-cellulose lacquer as being integral to the engraving process.

Nitro-cellulose lacquer is great stuff. It was used to paint '57 Chevys and '57 Stratocasters. Jackson Pollock was also fond of its qualities, fast flowing, quick drying and glossy. The fumes will give you(and everyone in your town) a headache, though. Anyone who is re-painting classic Leicas these days should definitely be using it. One of its best qualities, long known to electric guitar enthusiasts, is how beautifully it wears. In the U.S. it was sold by DuPont under the name "Duco"(long since gone). These days it is banned in most states for industrial use, but still available to individuals.
 
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Woods is one of the Eutectic alloys - it is characterised by having a melting point lower than each of its constituent parts - also check out Fields metal, which is also a bismuth alloy, and melts at a lower temperature again.

I have yet to try it, but you are suppsed to be able to make something approaching Fields metal by melting together equal weights of bismuth and tin/lead solder. For the experimenter, the solder should be easily available, and shotgun pellets are almost pure bismuth these days. I'm told you can do it in a stainless steel spoon with a hand blowtorch.

Who's going to be first to try it? :D
 
So , this is the infill on my 1st / 2nd batch Leica II ' twins ' ? .... and why it is '' smeared '' with age ?
 
Wow, that`s some "good reading" :D

Yes, I`m been aware of the "WoodmetalWismuth* technique for a while now, all the Grey painted IIIC`s and the IIIC K`s had filled engravings, anything that`s white or deep, is touched up/repaired.

I just got a tip, about a man in Australia who`s restoring pre 1950 Painted Leica`s, and is accessable only by snail mail, so I`m writing soon.....

I would love to see someone do a paintjob finish as good as originals on a 1930`s Leica, these cameras were 100% Nitro-Lack and were the same paints used when shooting the first VW beetles that rolled out of the factory for the REME in 1946, a deep (you can shave yourself like a mirror) lacquer, that was stumph untill you pollished it up and then it looked that glass!

Boy!!!! Them`s were "the good ole daze"! ;)

Tom
 
So, on the basis of the above, the principle of tickling the engraving with a little heat to 'bring it up' sounds feasible.

Problem will be the state of the paint and looking around for something to practice on.

So I'm after a top housing or similar that has been butchered in some way (shame, there was a box full on Ebay a few months ago) that can act a gineau pig.

Broken rangefinder? Ploot? The more I think about it I realise that this technique is only used on a few small items.

Not sure wether to try a soldering iron from behind or just a tiny touch with a small flame from the top.

Mind you I have some pretty dreadful camera bases that wouldn't look much worse if they were burnt!

Michael
 
TopPlate76.jpg


Here`s details on the top plate on a 1945 IIIC K Grey, it had lot`s of wear and tear and
was well by far the worst condition of any Grey K`s I`ve ever owned, it`s interesting, though that you can see where parts of the "woodsmetal" have completely fallen away....

But also in being very hard to photograph (the Grey paint cameras) the filling is really an off while color and not as bright as in the photos and it get`s this look by simply aging.;)

My 1942 IIIC/IIIFBD Grey Conversion, had it`s top refreshened at the factory in the early 1950`s and you can clearly see that by then the factory had gone to filling up engraving tops with white paint :(

Tom

PS: ohh BTW The serial numbers been censored too for online safety :)
 
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Tom, this is the woodsmetal finish. Admittedly worse for wear but it shows the process better than an immaculate one. Please take note of the P in DRP, you can see the infill quite clearly. The deterioration of the black cellulose close to the engraving is quite common

It looks to me like the K camera you show has paint of some sort that has been discolored over time by contact with the brass beneath. This is similar to the postwar so-called 'white dial' conversions where the white tends to go off colour.

Michael
 
Michael,

Unfortunately, I can't see your pic - could you check it's posted OK?

Thanks ;)

Oh - and on Woods metal, we're talking melting at 98 deg C, so you would have to be pretty handy with a torch to avoid it all running off onto the floor :eek:
 
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Dralowid said:
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Tom, this is the woodsmetal finish. Admittedly worse for wear but it shows the process better than an immaculate one. Please take note of the P in DRP, you can see the infill quite clearly. The deterioration of the black cellulose close to the engraving is quite common

It looks to me like the K camera you show has paint of some sort that has been discolored over time by contact with the brass beneath. This is similar to the postwar so-called 'white dial' conversions where the white tends to go off colour.

Michael
Click to expand...

Yes, that was a very well used camera ~ that spent alot of it`s years in a case, which didn`t help the condition/aging process....
(a US Army Major, photographed postwar Germany with it) ~ *in mid/late 1945*

I have another three cameras coming soon in the mail, I`ll be posting photos.

Tom
 
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