Seeking advice on glueing the 45 deg mirror under the field aperture back in place (Zeiss) - Solved.

Everything relating to microscopy hardware: Objectives, eyepieces, lamps and more.
Message
Author
Hobbyst46
Posts: 3113
Joined: Mon Aug 21, 2017 9:02 pm

Seeking advice on glueing the 45 deg mirror under the field aperture back in place (Zeiss) - Solved.

#1 Post by Hobbyst46 » Mon Apr 16, 2018 9:10 pm

Hello all,

1)

In my Zeiss standard scope, The view of the condenser phase plate through the phase telescope disappeared, and apparently the illumination changed. I disassembled the field aperture unit and discovered that the 45 degrees mirror, that shifts the horizontal light beam upwards towards the condenser, has detached from its flat metal carrier frame. It is a 60-70 years old assembly! the original glue was perhaps asphalt, since it is black and shiny. The mirror was glued onto two thin (1mm thick) cork strips. Those are glued to the metal surface (I do not see with what stuff).

The mirror is an ordinary 35x40x3mm glass mirror and now I see that the silvered side is in bad shape- especially along the sides, where the cement was - and must be replaced.

Is super-glue the suitable cement for it? the problem with RTV and other silicone cement is the difficulty to smear a very thin layer. With super-glue it is easier. But I am not sure about its compatibility with ordinary mirrors, and the cork strips - who knows. I have no idea if I should replace the strips and with which easily available material, keeping the flatness and thickness as they are now.

Will appreciate advice!

2)
One more question to the experts.
Closing and opening the field aperture is less smooth than it used to be. I do not believe that this is related to the mirror being loose. Anyone ever disassembled this Zeiss standard part? I prefer not to take apart shutters and irises, but perhaps re-lubrication is a must? The three screws on top of the field aperture ring are very obstinate, and the screwdriver just fails.

Thanks in advance
Last edited by Hobbyst46 on Tue Apr 17, 2018 8:58 pm, edited 1 time in total.
Zeiss Standard GFL+Canon EOS-M10, Olympus VMZ stereo

apochronaut
Posts: 3831
Joined: Fri May 15, 2015 12:15 am

Re: Seeking advice on glueing the 45 deg mirror under the field aperture back in place (Zeiss)

#2 Post by apochronaut » Mon Apr 16, 2018 9:54 pm

I've done 6 or 7 on other type of scopes. If it is an ordinary mirror and not a first surface, using a super adhesive type of glue might potentially strip the aluminum backing. I prefer a more plasticky type of adhesive, putting enough on so that it builds a small bead covering a small strip on the back and all along the sides for extra purchase on that rough edge of glass. I've always used 5 minute epoxy, applied with a small spatula, flat end of a toothpick, tiny screwdriver, etc.

Hobbyst46
Posts: 3113
Joined: Mon Aug 21, 2017 9:02 pm

Re: Seeking advice on glueing the 45 deg mirror under the field aperture back in place (Zeiss)

#3 Post by Hobbyst46 » Mon Apr 16, 2018 10:00 pm

Thanks a lot, Apochronaut!
Zeiss Standard GFL+Canon EOS-M10, Olympus VMZ stereo

Charles
Posts: 1355
Joined: Mon Mar 02, 2015 11:55 pm

Re: Seeking advice on glueing the 45 deg mirror under the field aperture back in place (Zeiss)

#4 Post by Charles » Mon Apr 16, 2018 11:21 pm

All the field aperture mirrors on my Zeiss are not glued on. There should be a metal back plate which holds the mirror in place.

Also the iris should never be lubricated and should be kept bare metal. There are two sets of three screws on the top. The three very small screws on the ring which keeps the glass lens in place and then there are the three larger screws near the rim which will allow you access to the iris leaves if they need cleaning.

GaryB
Posts: 77
Joined: Tue Sep 05, 2017 10:33 am

Re: Seeking advice on glueing the 45 deg mirror under the field aperture back in place (Zeiss)

#5 Post by GaryB » Tue Apr 17, 2018 3:37 am

One other thing with superglue, it can frost enclosed surfaces as it dries, ruining the mirror, lenses and iris. The cork might be for expansion with temperature changes and the 'glue' might well be bitumen. Post a picture of the parts, it'll be easier to advise.

Hobbyst46
Posts: 3113
Joined: Mon Aug 21, 2017 9:02 pm

Re: Seeking advice on glueing the 45 deg mirror under the field aperture back in place (Zeiss)

#6 Post by Hobbyst46 » Tue Apr 17, 2018 6:14 am

@Charles
@GaryB
Thanks. Here are photos. The brownish color of the strips (carrier frame, middle item) is the part of the corkstrip that is not covered with the black bitumen/asphalt.
On the field aperture, only the relevant screws are visible. They are obstinate and resist my screwdriver. The tiny black screws that retain the glass are hidden in the background.
I wonder if there is a simple way to align the mirror as accurately as possible while gluing it to the carrier.

Update: The glazier, who kindly cut for me replacement mirrors for a small fee, suggested that I use either contact cement or silicon rubber cement. Both are somewhat flexible even when hardened, but contact cement bonds the parts together immediately such that post alignment becomes impossible. Epoxy is better in this respect but, once hardened, is difficult to remove if neccessary. So, having already dropped superglue, it all depends on the possibility of alignment while the cement has not yet hardened.
Attachments
mirror (back side) carrier and field aperture.jpg
mirror (back side) carrier and field aperture.jpg (125.97 KiB) Viewed 4435 times
mirror (front side) carrier and field aperture.jpg
mirror (front side) carrier and field aperture.jpg (131.78 KiB) Viewed 4435 times
Zeiss Standard GFL+Canon EOS-M10, Olympus VMZ stereo

MichaelG.
Posts: 2586
Joined: Mon Apr 10, 2017 8:24 am
Location: NorthWest England

Re: Seeking advice on glueing the 45 deg mirror under the field aperture back in place (Zeiss)

#7 Post by MichaelG. » Tue Apr 17, 2018 8:47 am

Looking at the original construction, and its failure, I cannot believe that the mirror alignment is hyper-critical.

I would probably clean off all the cork and adhesive and substitute some of the adhesive foam, in pads or strips, that is specified for fixing domestic Mirror Tiles.

Edit: This might be the ideal material ...
https://www.wholesaleglasscompany.co.uk ... -08mm.html

MichaelG.
Too many 'projects'

Charles
Posts: 1355
Joined: Mon Mar 02, 2015 11:55 pm

Re: Seeking advice on glueing the 45 deg mirror under the field aperture back in place (Zeiss)

#8 Post by Charles » Tue Apr 17, 2018 10:47 am

The position of the mirror is not critical. The angle of the frame and screwing in the back plate will give you the proper angle. The cork backing with the back plate and not glue, is what keeps the mirror in place. I think the 'glue' you see, is what is holding the cork in place. You may need to replace the cork.

For the screws, you need to make sure you have the proper fitting screw driver. The slots are more slender than regular screw driver blades. If you can't find a proper fitting screw driver, you may need to file down the blade to fit.

Hobbyst46
Posts: 3113
Joined: Mon Aug 21, 2017 9:02 pm

Re: Seeking advice on glueing the 45 deg mirror under the field aperture back in place (Zeiss)

#9 Post by Hobbyst46 » Tue Apr 17, 2018 12:11 pm

Thanks again Apochronaut, Charles, GaryB, MichaelG for the kind and rapid help.

I decided against fast glue, contact glue, removal of the cork strips, and against using oil or other liquids on the aperture ring..
Found in the cupboard a 1" double-sided, spongy, 2mm thick, heavy-duty mounting tape (an imitation of a 3M product I believe). Cut a large piece that can sit on the back of the mirror between the cork strips. Now the mirror is affixed to the tape, it does not rest on the cork strips since they are only 1mm thick. This is temporary but. if proves to withstand the test of time and heat, may become a long-term solution. I also checked, with an accurate thermocouple thermometer, the heating effect of the 10W LED that seats quite near the mirror. When the lamp is on and at 100% duty cycle, it raises the temperature of the mirror frame by 10C at most.
Time to acquire a set of professional car-garage screwdrivers. So far, the flat screwdriver blade of the Swiss Army Knife and Watchmaker's screwdrivers did the job...

Phase contrast returned, so back to the marine organisms!
Zeiss Standard GFL+Canon EOS-M10, Olympus VMZ stereo

User avatar
75RR
Posts: 7593
Joined: Sun Oct 12, 2014 2:34 am
Location: Estepona, Spain

Re: Seeking advice on glueing the 45 deg mirror under the field aperture back in place (Zeiss)

#10 Post by 75RR » Tue Apr 17, 2018 12:45 pm

Sorry - bit late to the party.
I have taken mine apart. It had no glue, just pressed against the cork strips by the backing plate.
Your solution should be fine, I suspect the cork has lost a bit of its thickness.
Time to acquire a set of professional car-garage screwdrivers.
You need something more delicate than that.
I gave up on my car-garage screwdrivers [though I still used them on the car of course] and bought some Wiha.
Precision tools for a precision instrument. Very happy with the purchase.
Attachments
Wiha(1).jpg
Wiha(1).jpg (172.71 KiB) Viewed 4395 times
Zeiss Standard WL (somewhat fashion challenged) & Wild M8
Olympus E-P2 (Micro Four Thirds Camera)

Hobbyst46
Posts: 3113
Joined: Mon Aug 21, 2017 9:02 pm

Re: Seeking advice on glueing the 45 deg mirror under the field aperture back in place (Zeiss)

#11 Post by Hobbyst46 » Tue Apr 17, 2018 1:08 pm

Thanks 75RR for your help.
I will look for these tools or equivalents if I cannot find them locally. Do you know if Wera tools are good enough?
Zeiss Standard GFL+Canon EOS-M10, Olympus VMZ stereo

User avatar
75RR
Posts: 7593
Joined: Sun Oct 12, 2014 2:34 am
Location: Estepona, Spain

Re: Seeking advice on glueing the 45 deg mirror under the field aperture back in place (Zeiss)

#12 Post by 75RR » Tue Apr 17, 2018 1:13 pm

Wera are also very good. Got mine here: https://www.kctoolco.com/
Zeiss Standard WL (somewhat fashion challenged) & Wild M8
Olympus E-P2 (Micro Four Thirds Camera)

MicroBob
Posts: 2389
Joined: Sun Dec 25, 2016 9:11 am
Location: Northern Germany

Re: Seeking advice on glueing the 45 deg mirror under the field aperture back in place (Zeiss)

#13 Post by MicroBob » Tue Apr 17, 2018 7:47 pm

Do your replacement mirrors have the same thickness as the original?

Hobbyst46
Posts: 3113
Joined: Mon Aug 21, 2017 9:02 pm

Re: Seeking advice on glueing the 45 deg mirror under the field aperture back in place (Zeiss)

#14 Post by Hobbyst46 » Tue Apr 17, 2018 8:31 pm

MicroBob wrote:Do your replacement mirrors have the same thickness as the original?
Hello Bob. Yes, a 3.0-3.1mm thickness. Cut from scrap but high quality mirror, cost about 3$ a piece.
Zeiss Standard GFL+Canon EOS-M10, Olympus VMZ stereo

PeteM
Posts: 1424
Joined: Tue Dec 06, 2016 6:22 am
Location: N. California

Re: Seeking advice on glueing the 45 deg mirror under the field aperture back in place (Zeiss) - Solved.

#15 Post by PeteM » Tue Apr 17, 2018 10:43 pm

Not sure about your Zeiss, but many microscopes use a first surface mirror to avoid the possibility of a double reflection of the filament.

Hobbyst46
Posts: 3113
Joined: Mon Aug 21, 2017 9:02 pm

Re: Seeking advice on glueing the 45 deg mirror under the field aperture back in place (Zeiss) - Solved.

#16 Post by Hobbyst46 » Tue Apr 17, 2018 11:01 pm

PeteM wrote:Not sure about your Zeiss, but many microscopes use a first surface mirror to avoid the possibility of a double reflection of the filament.
I am not sure either, this microscope has a history about which I know nothing, except that for several years at least, it was routinely maintained by the local Zeiss agency technicians. Had they replaced a mirror, they would have done it according to the strict Zeiss manual. In fact, I am lucky that the second surface mirror works - I dislike handling first surface mirrors since they are so sensitive. Thanks for the input.
Zeiss Standard GFL+Canon EOS-M10, Olympus VMZ stereo

MicroBob
Posts: 2389
Joined: Sun Dec 25, 2016 9:11 am
Location: Northern Germany

Re: Seeking advice on glueing the 45 deg mirror under the field aperture back in place (Zeiss) - Solved.

#17 Post by MicroBob » Wed Apr 18, 2018 7:52 am

I can have a look into a GFL mirror unit. Since the Zeiss GFL mirror unit has one frosted lens surface, it might have been no problem to use a standard mirror in the design. Changeing from one type to the other would be a problem though.
Newer surface mirrors are not really that sensitive.
Polaroid cameras and microfiche readers are cheap sources for first side mirrors.

Hobbyst46
Posts: 3113
Joined: Mon Aug 21, 2017 9:02 pm

Re: Seeking advice on glueing the 45 deg mirror under the field aperture back in place (Zeiss) - Solved.

#18 Post by Hobbyst46 » Wed Apr 18, 2018 8:39 am

MicroBob wrote:I can have a look into a GFL mirror unit...Newer surface mirrors are not really that sensitive.
Polaroid cameras and microfiche readers are cheap sources for first side mirrors.
If not too much trouble, I would be glad to receive more accurate and specific information about the mirror. I have the Zeiss manual (in fact, brochure) for it and for the similar W and some other standard models, did not find specific reference to the mirror - let alone to maintenance! Thanks in advance.
My experience with first surface involves silver- and gold- coated IR mirrors. Just one more wipe with a Q-tip and...
Zeiss Standard GFL+Canon EOS-M10, Olympus VMZ stereo

User avatar
75RR
Posts: 7593
Joined: Sun Oct 12, 2014 2:34 am
Location: Estepona, Spain

Re: Seeking advice on glueing the 45 deg mirror under the field aperture back in place (Zeiss) - Solved.

#19 Post by 75RR » Wed Apr 18, 2018 11:31 am

can't give any technical details but can confirm they are first surface mirrors
Attachments
first surface mirror 2.jpg
first surface mirror 2.jpg (89.19 KiB) Viewed 4303 times
first surface mirror.jpg
first surface mirror.jpg (92.32 KiB) Viewed 4305 times
Zeiss Standard WL (somewhat fashion challenged) & Wild M8
Olympus E-P2 (Micro Four Thirds Camera)

Hobbyst46
Posts: 3113
Joined: Mon Aug 21, 2017 9:02 pm

Re: 45 deg mirror replacement of Zeiss illuminator - temporarily solved.

#20 Post by Hobbyst46 » Wed Apr 18, 2018 12:42 pm

Thanks a lot 75RR!

Wow, that changes the picture (pun).
The original cork strips are indeed thicker than on my mirror frame.
Apparently, a guy who once fitted a replacement mirror on my scope decided to use a second-surface mirror instead, and might have tempered with the strips as well.

Questions:
1. I have a hand-held Jencons diamond-coated glass cutting "knife". The size of a credit card, 5mm thick. Can it cut a first-surface mirror without damage to the coating?

2. @75RR, would you be so kind as to provide the dimensions of the original mirror and the thickness of the cork strips.
Zeiss Standard GFL+Canon EOS-M10, Olympus VMZ stereo

apochronaut
Posts: 3831
Joined: Fri May 15, 2015 12:15 am

Re: Seeking advice on glueing the 45 deg mirror under the field aperture back in place (Zeiss) - Solved.

#21 Post by apochronaut » Wed Apr 18, 2018 1:09 pm

You can use dental photographic mirrors to cut mirrors from. The stainless steel ones are obviously first surface and give close to 100% reflectivity.
https://www.ebay.com/itm/Dental-Orthodo ... Swp-RaTv9s

Hobbyst46
Posts: 3113
Joined: Mon Aug 21, 2017 9:02 pm

Re: Seeking advice on glueing the 45 deg mirror under the field aperture back in place (Zeiss) - Solved.

#22 Post by Hobbyst46 » Wed Apr 18, 2018 1:25 pm

apochronaut wrote:You can use dental photographic mirrors to cut mirrors from. The stainless steel ones are obviously first surface and give close to 100% reflectivity.
https://www.ebay.com/itm/Dental-Orthodo ... Swp-RaTv9s
Thanks for the idea. Stainless is easier handled than glass...However, I do not find the dimensions of this dentistry mirror.
I imagine that if it is very thin, I could perhaps attach it to the glass mirror that will serve as mechanical support.
Zeiss Standard GFL+Canon EOS-M10, Olympus VMZ stereo

MicroBob
Posts: 2389
Joined: Sun Dec 25, 2016 9:11 am
Location: Northern Germany

Re: Seeking advice on glueing the 45 deg mirror under the field aperture back in place (Zeiss) - Solved.

#23 Post by MicroBob » Wed Apr 18, 2018 1:44 pm

Hi Doron,

Zeiss frequently made small changes to the instruments so I would suggest to first try to find our how well the old mirror works. It might be original for your specific microscope.
If you install a small object in the middle of the frosted lens you might be able to see through the microscope whether it actuall is visible in the middle.
You could also test whether a piece of paper on the field iris shows the dot at the right position. The difference between front side and back side of a 3mm mirror at 45° is 4,24mm, so easily visible.

Glass cutting: The mirror coating may make the surface somewhat slippery so that you could easily get off track when cutting the mirror.
Is it a glass based mirror? I would make a few test cuts on old slides before I would tackle the job.
It will probably not be visible it your cuts are not completely precise.
Theory is that for thin glass you would use a cutter with a small wedge angle. Use oil on the cut and break it of quickly after scoring it.

Bob

apochronaut
Posts: 3831
Joined: Fri May 15, 2015 12:15 am

Re: Seeking advice on glueing the 45 deg mirror under the field aperture back in place (Zeiss) - Solved.

#24 Post by apochronaut » Wed Apr 18, 2018 1:51 pm

Hobbyst46 wrote:
apochronaut wrote:You can use dental photographic mirrors to cut mirrors from. The stainless steel ones are obviously first surface and give close to 100% reflectivity.
https://www.ebay.com/itm/Dental-Orthodo ... Swp-RaTv9s
Thanks for the idea. Stainless is easier handled than glass...However, I do not find the dimensions of this dentistry mirror.
I imagine that if it is very thin, I could perhaps attach it to the glass mirror that will serve as mechanical support.
The dimensions are large enough for your purposes. There are 6 or so shapes, designed to photograph certain sections of the mouth but even the smallest one is larger than you need, at around 100mm x 50 and 30mm. Search, stainless steel orthodontic photographic mirror and various shapes will come up, even sets. The prices are ridiculously low. There are also glass versions, which are not first surface, and oddly a few of the stainless listings, actually show pictures of glass mirrors??
The thickness of the stainless is not provided but you can see from the photographs that it is pretty heavy gauge. These are designed for autoclaving and continual reuse, so they can't be thin enough to easily bend , plus they are actually nickel/chrome plate on stainless. Reflectivity, very high.

Hobbyst46
Posts: 3113
Joined: Mon Aug 21, 2017 9:02 pm

Re: Seeking advice on glueing the 45 deg mirror under the field aperture back in place (Zeiss) - Solved.

#25 Post by Hobbyst46 » Wed Apr 18, 2018 2:08 pm

Thanks Apo' for the idea. Is well worth trying. I ordered it.
Do you recommend that I cut it on a milling machine to avoid distortion and damage to the coating, or is there another way?
Zeiss Standard GFL+Canon EOS-M10, Olympus VMZ stereo

User avatar
75RR
Posts: 7593
Joined: Sun Oct 12, 2014 2:34 am
Location: Estepona, Spain

Re: Seeking advice on glueing the 45 deg mirror under the field aperture back in place (Zeiss) - Solved.

#26 Post by 75RR » Wed Apr 18, 2018 2:15 pm

Cork is about 1-1.5mm thick
Mirror dimensions are - note that there are slight differences between the two mirrors:
Both rest snugly on their respective base, they are not however interchangeable. Note that the square mirror base has a larger indent at the top than the beveled one.

35.6 x 41 x 3.2 (Beveled mirror)
36.1 x 40 x 3.2 (square mirror)
Attachments
Mirror-4.jpg
Mirror-4.jpg (57.58 KiB) Viewed 4276 times
Mirror-3.jpg
Mirror-3.jpg (57.27 KiB) Viewed 4276 times
Mirror-2.jpg
Mirror-2.jpg (55.12 KiB) Viewed 4276 times
Mirror-1.jpg
Mirror-1.jpg (55.11 KiB) Viewed 4276 times
Zeiss Standard WL (somewhat fashion challenged) & Wild M8
Olympus E-P2 (Micro Four Thirds Camera)

MicroBob
Posts: 2389
Joined: Sun Dec 25, 2016 9:11 am
Location: Northern Germany

Re: Seeking advice on glueing the 45 deg mirror under the field aperture back in place (Zeiss) - Solved.

#27 Post by MicroBob » Wed Apr 18, 2018 2:23 pm

You could cut the stainless steel sheet with an angle grinder with a 1mm cutting disc. Many light passes to avoid heat and distortion and protecting the front surface is important. About as good as on the milling machine (which doen't like sheet metal very much).

Hobbyst46
Posts: 3113
Joined: Mon Aug 21, 2017 9:02 pm

Re: Seeking advice on glueing the 45 deg mirror under the field aperture back in place (Zeiss) - Solved.

#28 Post by Hobbyst46 » Wed Apr 18, 2018 2:43 pm

Thanks Bob.
I have a Dremel-like tool. Protect the coating with thick cellotape.. Or perhaps I can sandwich the metal plate between wood plates and cut through...
Zeiss Standard GFL+Canon EOS-M10, Olympus VMZ stereo

MicroBob
Posts: 2389
Joined: Sun Dec 25, 2016 9:11 am
Location: Northern Germany

Re: Seeking advice on glueing the 45 deg mirror under the field aperture back in place (Zeiss) - Solved.

#29 Post by MicroBob » Wed Apr 18, 2018 8:12 pm

Cutting wood with an abrasive wheel generates lots of smoke - I would prefer the tape.
You can glue a strip of wood on the tape as a guide.

Have you tried whether you really need a first surface mirror?

apochronaut
Posts: 3831
Joined: Fri May 15, 2015 12:15 am

Re: Seeking advice on glueing the 45 deg mirror under the field aperture back in place (Zeiss) - Solved.

#30 Post by apochronaut » Wed Apr 18, 2018 9:05 pm

Hobbyst46 wrote:Thanks Apo' for the idea. Is well worth trying. I ordered it.
Do you recommend that I cut it on a milling machine to avoid distortion and damage to the coating, or is there another way?
Do you know anyone with a shear? Make an oversize shirt cardboard cover, tacked in at least 8 spots around the perimeter with a tiny dab of some glue.
Mark your dimensions on the cardboard + a bit for dressing. Do some tests on a waste area first. Cut with a shear and finish it with a good fine file.

Good quality hand shears should do about as good a job, if the gauge is light enough ; about up to 16, for long ones. Leave enough extra so any small deformities, can be filed or ground away, down to the finished dimension.

I guess, first see what the gauge is. From the picture, it looked to be about 16.

Post Reply