Archived posting to the Leica Users Group, 1999/08/02
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]David, What you have managed to wear down to is the nickel plating under the black chrome. Another couple of 1000's of rolls should reveal the brass! The black chrome is applied over a layer of nickel on the brass, this serves as a sealer and it also makes the black chrome salt (Eloxal, a Leitz product) adhere better. To my knowledge, there were no recessed housings made from zinc-alloy and I suspect that the flush windows were a design feature that was necessitated by the casting. Recessed windows would have forced the manufacturer of the top-plate to make a casting form that split down the middle, otherwise the form would not release the finished casting. This would have resulted in a "spine" down the center of the top-plate and further machining. My old M4-P has a couple of brassy patches on it were the nickel plating has been worn through. The black chrome is sensitive to wear and you can quickly get the "silver" edges on a body but the nickel is quite tough and resists wear quite well. The reason you don't see this on the chrome bodies is that it has the same color as the chrome finish and it is also possible that Leitz applied the chrome directly to the brass. The black chrome is a different compound than the regular chrome plating. Black chrome plating involves nasty stuff like hydrochloric acid and cyanide (not in the same bath though!) and very strong electrical charges going through it. Definitely not a kitchen counter job. Tom A Subj: [Leica] re: m4-p questions Date: 8/2/99 11:48:41 AM Pacific Daylight Time From: duffdl@uswest.net (David L. Duff) Sender: owner-leica-users@mejac.palo-alto.ca.us Reply-to: leica-users@mejac.palo-alto.ca.us To: leica-users@mejac.palo-alto.ca.us Hello Tom A. and group. Tom's answer got me looking at my M4-P which has been showing what I would call "zincing" (similar to brassing?) for years. My camera #1605xxx, has the old, recessed windows of the earlier M4-P's and M4-2's, not the flush windows of the M6. But the "zincing" is definitely "silvery", not brass colored (like under the chrome of my M3 and IIIf's). So my question, do flush windows necessarily indicate a zinc top plate? Or is there a silvery coating under my black chrome before I get down to the brass? Just for my own info. Thanks, David Duff, BS, CFA, xCRA, LHSA, MOUSE.