Re-silvering mirrors?

[Tin]

Another thing though. Aluminium oxidizes with time. You will really want to stick with silver

Yes, aluminum oxidizes with time, but silver tarnishes much much faster, especially in places where the pollution level is high (sulphur dioxide, hydrogen sulphide). That is why silvering telescope mirrors are only done by amateur beginners. Nowadays, there are commercial labs that does aluminising that the more advanced amateur telescope makers would use their service rather than doing silvering themselves. In the old days, of course that was another story. Silvering was the only means available to amateurs.

 

[mooge]

haven't had much time recently but I left the test piece in the solution and I noticed that the silver seems to have tarnished. Or something. it's a dark sort of colour... actually, I've never gotten a good metallic silver out of it. maybe my solutions are bad? what's going on?

and the silver nitrate solution stains pretty bad. I've had black specks on my fingers for the past like three days. Worse is that I got some on the kitchen table. somebody isn't too pleased...

 

[Tin]

haven't had much time recently but I left the test piece in the solution and I noticed that the silver seems to have tarnished. Or something. it's a dark sort of colour... actually, I've never gotten a good metallic silver out of it. maybe my solutions are bad? what's going on?

and the silver nitrate solution stains pretty bad. I've had black specks on my fingers for the past like three days. Worse is that I got some on the kitchen table. somebody isn't too pleased...

I couldn't give you a good answer for the first part of your question. Perhaps it was due to impurities of some sort. did you use clean equipment, pure chemicals, and distilled water? Those are the probable culprits that I can think of off the top of my head. I had never experienced such bad results.

With regards to the staining, those are caused by silver deposits. You can clean those with dilute nitric acid. And of course remember to wear a pair of vinyl gloves next time you do this again. Also the silver nitrate solution do not keep for too long, so next time around you should just make up as small a portion as is needed.

 

[mooge]

AHA! this looks promising!

what changed? I don't really know. it's a bit colder today, maybe 21 degrees instead of 25. I put the B solution in before the A solution. I didn't agitate as much. and I cleaned the glass with hand soap (oh yes).

curiously, the non-glass side is a coppery sort of colour (seen on the edge of the glass there; I'm coating both sides and wiping one). perhaps from copper contamination? I used a copper-plated key to get the silver nitrate crystals out of the impossibly tiny bottle... and there was definitely some reaction going on and I guess a bit of copper entered the solution. Not really a dealbreaker I suppose because it only occurs on the less important side...


tomorrow, time and transmission tests. Heck, I'll do some right now.

exciting! (well sort of...)



also perhaps worth noting: this solution is a week old. and it works! well, sort of.

 

[kuzano]

Certo6 on eBay

Certo6 on eBay

I seem to recall Jurgen re-silvering a mirro for me on a Mamiya Six rangefinder. He has for certain replaced the bellows on two of my Mamiya Six folders and I have one to re-assemble that I am pretty sure he did the mirror in the range finder, as a separate job, sent to him specifically for that purpose.

Time flies when you're losing traction on your memory:bang:

 

[mooge]

never mind time trials... until 10 or 11 minutes, nothing happens, and at 15 minutes, the coating's too heavy.

and anything before 15 minutes, the coating is too uneven.

look and see I guess. and prepare that surface!




I've got quite a bit of solution though... it's maybe 3mL of each per trial, and I made 200mL of each. makes me wonder what else I could silver.
my watch? nah.
my glasses? nah.
my brother's brand new iphone 4? YES.

 

[mooge]

More silvering today, with the prism from the M2 finder.

I didn't bother timing this time; it varies if you're sloppy like me and don't measure out a perfect 50/50 of the A and B solutions. I just put the prism in, and checked every so often to see what was happening.

One of the factors that seems to contribute to surface quality / evenness of the silver is the temperature-- I guess it's the uniformity of the temperature of the glass that determines the uniformity of the silver deposition? I don't really know. But when I ran the prism under water (cold seemed to be better), the surface tended to be more uniform. which is not that uniform at all; in fact, uniformity seems to be one of the large hurdles in this experiment.

Old Canada balsam was cleaned off with acetone (someone's suggestion, sorry I don't remember who). it's worth noting that the prisms are covered in paint... and acetone dissolves paint. be careful...

Another observation: some aluminum refused to come off the prism so it served as the reference for the silver coating. it seems like for a given reflectivity of light, the aluminum is brighter than the silver. This is really weird. But that's what I observe: in the corner where the Al is, the image and reflection are brighter and in the silver region, the image and reflection are weaker. not good news!


Oh and a few notes on cementing with balsam:
1. make the jig before cementing... holding sliding prisms in one hand while bending wire with the other isn't so simple
2. one drop of balsam is probably too much already
3. taping over the surfaces of the prisms isn't a bad idea ( at least so far)
4. don't touch the optical surfaces if your fingers have balsam on them



so right now I've got a possibly acceptable mirror surface and the prisms are reunited at last (at least temporarily), next is some dry time (bake them??) and then some testing. if it's okay, it goes in the M2. if it's not, it gets separated and then re-silvered...

 

[Sarcophilus Harrisii]

Interesting discussion. Thanks for sharing your exploits.
Cheers
Brett

 

[mooge]

Okay.

So I also cemented the doublet that came apart (between the beamsplitter and framelines). The convex lens is asymmetric (sort of wedge-shaped) so I'm not really sure how it goes together. (more on this later).

Both beamsplitter and doublet were 'baked' in a dead car we have on our driveway. Temperature in the sun is maybe 60 degrees with the outside temperature being 24 or so. Baked for two days, the balsam is pretty hard; durable enough for fitting anyways.

Fitting was today and... it wasn't great.
First of all, the rangefinder-- rather cloudy and copper tinted (definitely copper contamination!), and oddly enough, the RF patch and framelines are tinted blue. Kind of cool. but the big problem is that there's virtually no contrast.

Second problem is that of range. I was going to put the camera together anyways and use it for a couple of days, but the RF won't focus down to 0,7m, so I can't even do that. I suspect it's due to some skew in the doublet, but I really don't know for sure. I spent a lot of time messing with the beamsplitter position to get it to work, but nothing really did.

So now both beamsplitter and doublet are sitting in acetone. The moment I put the beamsplitter in, the acetone started to go black. Great. So I have to repaint the prisms. And then there's the doublet-- I need to reposition one element but also I'll have to cement the concave element back into the metal frame.


man can be defeated, but not destroyed?








(^ it's ugly and it doesn't work.)

 

[mooge]

Well well well well well well well. Well.

I'm running out of time so I've slapped something together and that's what I'll be bringing on a 1.5 month trip. It's dark and tinted a disgusting shade of brown but it works. barely.

I made new A and B solutions, this time without copper contamination. And I don't think they worked; I only got a layer of silver maybe 3 times out of those solutions. I never filtered the precipitate out of any of the solutions and apparently it did have an effect on whether the reaction would work or not. And apparently the reaction does not like agitation. I really have no clue what I'm doing though.

More randomness-- some silver (not the copper silver) stuck to the prism and wouldn't come off. Usually the silver comes off with a wipe of a finger. This time it didn't. Fingernails didn't work either. Stop bath (weak acid) didn't help either. So I just left it there.
I couldn't get the uncontaminated silver solution to work (too much / not enough ammonia?) reilably so I used the new B solution with the old, copper contaminated A solution. A couple tries later, I got a splotchy, dirty silver layer that could work. So I cemented the prism together.

I didn't put enough balsam (too much last time) so to add to the unevenness, there's a scratch of missing silver from me trying to spread the balsam out. I baked the prism and the doublet for three days in a car. And it wasn't that sunny even.

Re-aligning, I came across the same problem as last time-- establishing the right range. Apparently I have no understanding of how the RF mechanism is supposed to be adjusted either, because the grub screws seem to draw the beamsplitter towards the machined rails that sit against the silvered prism face. So I kind of wedged it in with a shim of paper (I do this all the time, and like to claim that's another reason why I would make a good engineer) and tightened the screws gently. Now the mask behind the negative lens and in front of the splitter doesn't fit. Oh well.

But yeah, it works. It seems okay (well, just dark and brown) in lower light but if it's bright and your pupils are stopped down (so to speak), you can see all the unevenness of the silvering. It's gross, I'm not gonna lie.

My polaroid 250 has a much much better finder-- better contrast and brighter. Even my Kiev has a brighter finder. That's sad. But neither of those can take my Nokton 35.

What's sadder still is it's probably easier for me to buy another beater for $300 and fix it up (without removing the aluminum coating) instead of waiting five years for CRR to free up and then paying them $300.


So don't make the same mistake I did!
(unless you understand chemistry)...

 

[mooge]

And here's proof. The brown cast is not apparent due to a certain kind of magic known as "auto white balance".

In the end though I guess I shouldn't complain-- before, the finder was dim (ish) and lacked contrast; now it's just dimmer and the contrast of the RF isn't really any worse. Maybe even better. But it is at least a stop dimmer and this disgusting sort of uneven brown.



( And it's a stage 88 if you were wondering. With some dead notes... )

 

[Guest]

Some help

Some help

Hi, is this the part you are looking for¿?
If it's not, try Edmund Scientifics. Write them an email to see if they can source you with a similar part, given I doubt they will provide you with the same one.
Also, mailing Leica for spare parts it's ideal. There's an official dealer in NY they will redirect you from whom you can source original parts.

I hope this helps.

Marcos.