Any suggestions to re-balsam lens cells...? or I'm dreaming!

[Miguel Coquis]

Hi there !
Will much appreciate any help to find a way to save a lens cell from suffering "separation" (balsame I suppose).
Big heads (and old wolves, also owls !!!)) might have an idea of how or who or where, avoiding making a hole on pants pocket... :)
Lens is a very nice Tessar barrel 500mm with a beautiful iris opening particularly intersting for portraits.
Thanks in advance,
MAC

[Steven Tribe]

Is this one of the many Krauss versions of the 500mm Tessar?

For you, my friend, the cost would be mostly postage!!

[Miguel Coquis]

Wow !
That brings hope. It is in fact a Carl Zeiss Tessar portrait aereal lens f:5
It is relatively light weight which represnts a must when working ulf.
Any more data, please ask.

[Kevin Crisp]

It doesn't look like balsam failure to me, that is not the usual look or pattern.

Your choices are to live with it or recement it. As to the latter, your options are professional (Focal Point in CO) or do it yourself.

Can you get the affected element out of the mount?

[Miguel Coquis]

Looks more like kind of glue. Will try to dismount rear to see if affected element can come alone.

thanks !

[Jac@stafford.net]

Separating balsam cemented lenses is as easy as placing them in water and gently raising the temperature until they slide apart. Rinse in water as hot and done.

Centering them for recementing is a real challenge. Suggestions from others would be appreciated.

[Steven Tribe]

I think it is an early synthetic glue, which often shears like this. Replacement with balsam is more reliably done than with UV glue.

I wish one could do the separation as jac describes! It can take up to two weeks with nasty solvents. Hot water over a long time may (and does!) cause horrible damage.

Lens designers did think about making glueing easy and there is always a "best sequence" for complex lenses.

[Miguel Coquis]

Separating balsam cemented lenses is as easy as placing them in water and gently raising the temperature until they slide apart. Rinse in water as hot and done.

Centering them for recementing is a real challenge. Suggestions from others would be appreciated.

I am not sure of trying...
Included are few Pics for the affected element. I have to say how much I am impressed of the fine craft on the construction of this lens.
Very fine tiny little screws retaining rings at different levels, everything comes alone once them unscrewed. And the glass is like a "gem".
So, what kind of cement, who would provide it ?
And centering for recementing...
This should probably must go to Denmark ;)

[Steven Tribe]

Separation system is the same for balsam and synthetics.

The problem with water is that it is absorbed into glass and is full of very active H+ and OH- which react with the strange combination of chemicals that go under the name of optical glass.

[Miguel Coquis]

I think it is an early synthetic glue, which often shears like this. Replacement with balsam is more reliably done than with UV glue.

I wish one could do the separation as jac describes! It can take up to two weeks with nasty solvents. Hot water over a long time may (and does!) cause horrible damage.

Lens designers did think about making glueing easy and there is always a "best sequence" for complex lenses.

Steven, can you develop a little more about replacement with balsam being more reliably done than with UV glue.
Many thanks !

[c.d.ewen]

Read S. K. Grimes' methods (binocular prisms & v-blocks) here (http://www.skgrimes.com/library/old-news/old-lenses-can-be-restored-by-re-cementing).

Charley

[Kevin Crisp]

The two pieces of glass appear to be physically centered, which is really good news.

I don't agree that boiling is the best way to separate balsam but this looks like UV cure cement so it doesn't matter what I think on that point.

1. Separate it with a soak in a solvent like MEK or acetone. Be aware of the fire/fume danger with both. Since you're half way there already, and it will wick its way into the gap by capillary action it won't take weeks, maybe a few days. As it works you will see the cement turning cloudy and you can follow its progress. When nearly all there you can probably slide them apart.

2. CLEAN the glass. And I mean clean. With acetone. Surfaces must be totally clean and lint free. A final wipe with acetone and cheesecloth works well.

3. Get a UV cure cement from Summers Optical. With an appropriate drop or two (it doesn't matter if it leaks out the sides, but if you come up short you have to clean and do it again) put the two back together on a very level surface. Pop any bubbles in the cement before you stick the glass together. Touching the bubble with the tip of the cement bottle has worked for me in popping them. Give the glue time to seep out to the edges. If you are almost there, you can smear the cement a little by sliding the elements around very slightly, but you risk air getting in there. Sometimes if you are almost there you can gentle push the elements together. There is a feel you develop for how much cement it will take for a certain size lens, and unfortunately you're doing your first one. You may end up cleaning them off and trying again if you come up short. There is a learning curve unless you get really lucky.

4. Physically center the glass using machinists' V-Blocks.

5. Using an UV bulb (the compact florescent black light bulbs work) give it a short exposure. Maybe 30 seconds or so. You are just trying to hold the two parts tacked together. You can use a loose drop of the glue on a microscope slide to see how long that takes. Remove the blocks, inspect the evenness of the glue and the centering.

6. If good, then give it a good 30 minutes or so with the UV bulb. Turn it over and give it some more.

7. Clean off the edges with a very light wipe with acetone.

8. Reinstall in the mount.

There are special solvents made for the post-balsam cements, but they are very flammable, have to be heated, and there is a risk of breakage and fire. Be patient and stick with MEK or acetone.

[Miguel Coquis]

A shot with this old tessar on 14x17" negative:"le Vide Plein"

[Miguel Coquis]

[QUOTE=Kevin Crisp;1279099]The two pieces of glass appear to be physically centered, which is really good news.

Thanks Kevin for the complete protocol you just post !
I believe it would be very useful not only for me.

[Tin Can]

Kevin,

Thanks for the concise and useful post.

[Steven Tribe]

I have listed why I think UV glue is not a good idea for DIY before.
In short: expensive, very short shelf life, need protection for hands and eyes, mistakes ( which may become apparent after curing) means labourious delays, requires safe uv source when the sun doesn't shine.

I don't know whether you have done any lenses with old balsam separation Kevin, but the process you describe is quite inadequate for these! There are always deposited residues around the edges which are not soluable in either acetone or water.

[Jac@stafford.net]

I don't agree that boiling is the best way to separate balsam but this looks like UV cure cement so it doesn't matter what I think on that point.

It separates before reaching the boiling point of water at ~sea level.

As for the fanatical cleaning of the edges, use 800-grit wet/dry paper. Fer crying out loud, stop down 1/2 stop. And for finesse, we ain't gonna live long enough to suffer the consequences of the small stuff and your grandchildren will care less than nothing.

[Kevin Crisp]

I've had the best luck with this cement:

https://www.optical-cement.com/cements/cements/uv.html#anchor669157

I told Summers what I was working on and this was their suggestion. It does have a shelf life of a year, refrigerating it reportedly doesn't extend that, it does cost $36. They have cements with longer shelf life, but they require UV in the sunlight range so you're into getting a sun lamp instead of a cheap black light bulb. I think wearing gloves is smart and glasses too.

As to mistakes, yes getting the lens apart again if you fully cure it is time consuming. You might have to soak the elements for a week or two. It is much easier to separate them if you carefully inspect and find an issue, after just tacking them long enough as suggested. And if you have a bubble or incomplete coverage of the glue and you fully cure it, you've got your work cut out for you. I've got one protar where the cement did not quite fully get to the edge. Fixing it would have meant decementing the whole thing (4 lenses) and it works great as is and is stable so I've not redone it.

I have never tried using balsam to recement. I prefer not having to heat up the lens or cement.

[LabRat]

Big thumb's up to Kevin's post!!! That's what I have understood to do (but never got around to trying)...

A tip to tell what cement is holding it together; When held under a UV "blacklight" bulb, UV set cemented lenses have a VERY slight fog/glow look to them in the cemented area (even if they are assembled and you look into the front of the lens), where the balsam bonds do not glow...

Some light, even pressure is required while the cement sets... But difficult to apply correctly because the lens wants to slide around like a piece of polished ice on a convex mirror, and once pressure is applied for the first time, it cannot be released or bubbles can be drawn into the bond...

Using Canada Balsam for re-bonding is better, if the bond has to be re-done, VERY slowly heating/cooling it (to 140deg F), will release the bond so you can try again...

I would suggest sending it out for the service...

But I like the effect in the sample image!!! If the problem is bad and getting worse, send it out...

Steve K

[Kevin Crisp]

This person has an interesting method for separating balsam components, using a light bulb:

http://forum.mflenses.com/re-cementing-doublet-elements-with-canadian-balsam-t34467.html

I know because I discussed it with Mr. Grimes that he heated the elements dry and then slid them apart. Sometimes they broke.

The only method I've tried is: putting the element on scrunched up aluminum foil in the kitchen oven. Tilt it. Set the oven to 100F. Go higher slowly in stages about 10 degrees at a time. There will be a sudden moment when the kitchen smells like a clear cut forest. Check the oven for when the top element starts sliding off the bottom. Take them out and quickly help the separation with a tooth pick or two. Put them back in the oven and turn off the oven and let them slowly cool. I haven't broken any yet.

[LabRat]

Another makeshift oven that heats/cools very evenly/slowly is a large cast iron skillet filled with clean sand, and another smaller heavy pan that is put upside down (into the sand) as a cover... This is put on a stove and heated for a long time until the smell comes out...

correction; I mentioned 140deg F before, but I might be confusing it with the melting point of gelatin...

Steve K

[Kevin Crisp]

It has been a couple years since I've separated one in the oven. I remember it was north of 200 degrees. I want to say they really started sliding most of the way off at 230. So maybe boiling water would work. The skillet technique sounds a lot like what the late Mr. Grimes described to me over the phone.

[ruilourosa]

Hello!

I´ve been experimenting with some cheap zoom elements and some really busted lenses from the 30´s (german and japanese lenses). Boiling in water never separated any lens, nothing really happened apart from diluting the black paint around some lenses!

a one week dip of acetone separated most of the older ones.

a two to four week dip of diclorometane separated the rest of the lenses.

UV optical adhesive can be bought cheap on bay bay! and if the one you bought does not work unglue it and repeat with a different one.

centering... well you will have no problems centering that lens: put the concave element down, pour some glue, just a tiny in excess and put the convex element over it, if
you press a little the glue will act like a lubricant and self center the lens, or you can adjust the borders the best you can... i never had a problem with centering.

i have done 3 or 4 lenses, mostly not mine but i glued an angulon 165 that i use regulary, and it works really well.

I did however had tons of problems with dust, dandruff or whatever, be cautious!

[Steven Tribe]

Now this is good advice! Mirrors my experiences completely.

You can soften new balsam with heat, but old balsam is often very dry and gets even more solid when you heat. Problems with allignment is just an old wives' tale - even with four lenses.

[c.d.ewen]

I don't recall if someone mentioned this or not, but one usually scribes a mark on the outside edge of the two elements before separating, so that on reassembly they can be realigned the same way.

Charley

[Steven Tribe]

I don't recall if someone mentioned this or not, but one usually scribes a mark on the outside edge of the two elements before separating, so that on reassembly they can be realigned the same way.

Charley

Nope!
Everything is symmetrical and spherical. Marking is probably a good idea with complex cells, spacers and lens groups.

The typical thickness of the double convex in an achromat is less than 1mm. I have never seen allignment marks in any achromat which has obviously been redone earliar.

[Miguel Coquis]

Thanks all for the "savants" comments. It is really a interesting subject, optics....!
BTW, any info about refractive index differences between different glues (synthetic, ecologic, balsams...)?
Warm regards,
MAC

[Nodda Duma]

Personally I would not use Canada balsam, especially if you think UV adhesive is being used now. There are thermal and optical performance reasons for this.

Norland NOA 61 or NOA 68 is what we call out for bonding of doublets depending on the temperature requirements. Those adhesives have been used throughout the industry for years and years. I've never had any issues with that adhesive under temperature testing much more extreme than you'll likely ever see. Part of it also is when designing optics I'm careful to ensure the glasses that make up the doublets have thermal expansion coefficients within 2 ppm / C of each other. These doublets with failing bond joints likely don't have glass types as closely matched thermally. Even so, NOA 61 should hold up over the life of the lens if used correctly.

If you use a UV adhesive, purchase a dentist's UV cure wand. When you go to set the adhesive, give it a 3-4 second cure from about 1-2" away. Then verify centering. Once you're satisfied, UV cure exactly as the manufacturer describes in the instructions. Note: Taking longer to cure is better, assuming you can maintain constant temperature.

*Highly recommend* measure the runout before you debond the doublet and use that measurement as maximum acceptable runout when you rebond. Use a radial bearing and a test indicator setup or some other suitable method to measure. Note: A V-block won't really work.

If you already debonded the lens, ensure runout is 0.003" or less when you put them back together. That's a pretty typical centering tolerance for lenses in these types of applications.

If you have any confusion about this advice or feel you're not up to it, then send it out to be repaired professionally. Otherwise you will degrade the optical performance compared to what you had before. Of course in the end it's your lens to do what you will with. :)

[Kevin Crisp]

If you have a lens where an element is much wider than what you attach it to (sitting on top, like a toadstool) then you won't think centering issues are old wives' tales. Assuming old wives were into this sort of thing. Some of the Wolly wide angles are like that. Some protars are like that.

You can eyeball it with great care and sliding something around the edges to check for uniform spacing. Some people will gently install it in the mount, tack it with a little UV exposure, then take it out and check it. If you find the lens (before separation) to be less than perfectly aligned, you've got a quandry. Did somebody in 1924 screw it up at manufacture? Or does physical centering give you optical misalignment? Without fancier equipment like a laser table that Mr. Grimes used, I don't know how you answer that.

On dust, I use a little 12 volt computer fan to blow across the lens as I work so nothing settles on it. Put a piece of poly fluff on the intake side for filtering.

The good news that is stopping down to typical LF apertures eliminates or masks a bit of imperfection. Your work doesn't have to be perfect for the lens to be saved and perfectly useful. If you can afford it, send it to Focal Point they do outstanding work.

[Jac@stafford.net]

You can soften new balsam with heat, but old balsam is often very dry and gets even more solid when you heat. Problems with allignment is just an old wives' tale - even with four lenses.
Both points well taken, Steve. I guess I lucked out separating my lens, and was intimidated by persons discussing smaller lenses.

[Kevin Crisp]

Having thought about it, I don't think in an oven they slide apart until over 300 degrees. So boiling would never do it. I am about to tackle one so I will closely check for the temperature at which the elements slide apart.

[Jac@stafford.net]

Having thought about it, I don't think in an oven they slide apart until over 300 degrees. So boiling would never do it.

But it did.

[Kevin Crisp]

I'll try that first.

[Old-N-Feeble]

SIDESTEP: Is there any concern regarding boiling lens cells in extremely hard water? Would distilled water be better?

[LabRat]

As explained to me, the tough part is to unseat the elements to get them apart... The first thing is to check what is being used to bond them by using a "blacklight" lamp and seeing the glow/haze with a UV cure cement... Canada balsam will soften with just heat (unless as Steven mentioned, the balsam is old and hard)... But a UV cure bond requires a solvent soak, and usually at a higher temperature... (and MEK evolves heat, so there is heat involved...) The trick is how evenly that heat is applied, and allowed to cool... And polishing and re-coating processes involve heat... All this is hoping that the glass was well tempered without flaws and strains... (I was even concerned that a chip or scribe mark might be a source for a crack to form!!!) But I think that the glass started life as a molten mass, and all heat being even (for even expansion/contraction) and well tempered, it should be OK (but with the ever looming possibility that it can or might crack)...

I had been buying VERY cheap surplus lenses that had many flaws to practice operations & procedures on, come the day I had to do some serious optical work on a lens... The biggest headache I thought I was to encounter was a nice old Turner Reich 15" that had some minor separation/yellowing at the edges, that I assumed would get worse... But 35 years later, it hadn't changed, so I learned "if it ain't broke, don't fix it"...

Steve K

[Kevin Crisp]

There are a number of people who appear to have successfully separated modern lens cements with boiling water.

I would say separating the elements is relatively easy. Getting them clean, and centered, and recemented is the hard part.

[bobm4360]

Xylene is the solvent of choice for microscope users when dealing with balsam.
Ymmv,
Bob

[Steven Tribe]

I would say separating the elements is relatively easy. Getting them clean, and centered, and recemented is the hard part.

I have to say that I, based on numerous operations, find the reverse is the case. And much time is involved with separation compared with assembly.

The major problem is the build-up of solids around the edges which makes turning or pushing the lenses apart impossible before a lot of the old balsam has been dissolved through edge "bleeding".

[Steven Tribe]

Xylene is the solvent of choice for microscope users when dealing with balsam.
Ymmv,
Bob

As microscope slide makers have a more unbroken tradition ever since the 19th C than photographic lens repairers, their opinion means a lot. Xylene/Xylol isn't pleasant to work with!

[Kevin Crisp]

Put the lens in the oven, turn up the temp 10 degrees at a time, eventually the kitchen smells like a forest and the lenses slide apart. I push them all the way apart with toothpicks then let them slowly cool. I don't see what is difficult or time consuming there. It is technically no more difficult that dealing with a very slow cooking pizza. If your comment pertains to trying to use solvent to get them apart, I can't comment since I've not tried that on a balsam cemented lens. This seems easier than dealing with Xylene.

[Bernard_L]

@ Miguel Coquis.
The lab where I work uses UV curing glue. It is discarded every 6 months, as per manufacturer's recommendations. You can have, for the cost of postage, a just-discarded bottle of glue, provided you wait for the right time. Or, the one that was discarded last January, and kept in my fridge since then. I already sent some to a guy in Norway to re-cement something in the RF assembly of a 35mm camera, and he reported success.

If you are interested, send me a PM

[Old-N-Feeble]

Oh... now you've opened a big can of worms. You're gonna get hit a many requests. LOL!!

[Pierre 2]

Just found this link which should be of great interest, whatever bonding material is used.

http://web.archive.org/web/20070220153603/http://www.emsdiasum.com/summers/optical/cements/manual/manual.html

Pierre

[Randy]

After separating two elements a couple years ago (soaked for about 7 days in acetone) I just put a drop of vegetable oil between them and put the lens back together. No messing with glue / balsam. Sold the lens a year later and it was still clear. Told the buyer to just clean and replace the oil if it ever discolored. I think that may be a "Galli" trick...but not sure where I got it.

[Tin Can]

After separating two elements a couple years ago (soaked for about 7 days in acetone) I just put a drop of vegetable oil between them and put the lens back together. No messing with glue / balsam. Sold the lens a year later and it was still clear. Told the buyer to just clean and replace the oil if it ever discolored. I think that may be a "Galli" trick...but not sure where I got it.

That sounds very easy. Too easy. :)

I will try it sooner or later.

Why not?

[Steven Tribe]

Oil is the early telescope achromatic system. Another system was three very thin pewter strips at the edge of the lens. I had an early Frauenhofer telescope with this system which still worked OK.

[Bernard_L]

Another system was three very thin pewter strips at the edge of the lens(...) still worked OK
Balsam is specifically used because it has an index of refraction close to that of glass. Not so with air.

[RSalles]

MC,

Last time I planned to send a Voightlaender with balsam separation to this guy the service was rated at US$150.00,
https://www.facebook.com/CLAmanualfocuslens

Cheers,

Renato

[Steven Tribe]

Sending things for repair across trade barriers is full of problems and you are automatically under suspicion for attempted fraud.

[RSalles]

Yes, money laundry of 150 US bucks.

:)

Renato

[Nodda Duma]

Balsam is specifically used because it has an index of refraction close to that of glass. Not so with air.

Close to classic crowns and flints (1.5-1.6 or so). Not so much close to more modern glass types with indices of 1.7 or greater. For photographic objectives it's not as important. Very high performance designs have to account for the difference or they can run into trouble.

[Steven Tribe]

Miguel's lens does use Canada Balsam as the cement and should be as good as new in a few days. The edges have been blackened as is the custom these days. The first thing the solvent did was to remove the black , showing that the French tradition for pencil writing on the edges continued up into the 20th century!

I think that these later balsam jobs must have contained an additive or have been subject to refining, as there is no sign of the usual yellowing of the dried out edges. No quite so smelly, either.

[Steven Tribe]

And this is what the OP's lens looks like this morning!

It has a wonderful mount and the pencil 15 on the lens edge matches the marked XV on the aluminium mount. It also has a hole drilled through the mount in order to insert oil if the thread was difficult.

[Peter De Smidt]

Nice work!

[Miguel Coquis]

Magnifique !!!
Thanks a lottttttt... Steven for bringing this cell back to its original purpose, clean and save from "glucoma".
Will post more pics once the lens group will be mounted on its barrel.
Bravo LFF !

[R. Peters]

A friend used to re cement lenses. He'd put them together after applying cement, then roll the re cemented cell on a flat table so the edges were lined up. As I understand it, some lenses have elements that need to go back together exactly as they came out. Not only in the right order, but even in the same position (clockwise) relative to the other elements. The story goes that only one or two people could assemble a Dagor and align the elements to cancel out shortcomings. Which is why both front and rear cells carry the serial number. This also leads me to believe you might want to mark the edges of each element in the cell on the side as well as the mount so that the elements end up in the same position they were in before, relative to the other elements in the cell (Like their position on a clock). And so that the whole cell (front or rear) ends up in the same position it was in before, relative to the other cell. Modern lenses are mostly ground by computers, or so they tell me, so such concerns probably don't exist in modern lenses. Maybe someone else has more or better information.

[Steven Tribe]

This "rolling" of lenses sounds possible for some designs, but many post- rectilinear component lenses have a lens which is insert in a concave "hole" which finishes quite a few mm from the lens edge. Many Petzvals and fast Aplanats/RRs have very thin edged double convex lens which would not be suitable. The sense of touch is surprising good at noting irregularities.

I can't say much about later designs, but neither Petzvals or RRs are sensitive to the exact distance between cells. I just can't believe the comment about Dagor assembly, There are absolutely no adjustment possibilities in their cells.

[R. Peters]

The adjustment as explained to me is within each cell, turning each element against the next, not distance between elements.