Recementing lens element

[Jimi]

I have no idea where to put this, really, but here goes:

I have had the idea (on and off) to recement the rear element of an old brass Rodenstock (it's an Aplanat). It has balsam separation on the edge, and I am thinking of it as a project lens, as the element is very easy to take out. I guess sending it off to a specialist like John at Focal Point would be nice, but the value of the lens (apart from its sentimental value to me) is low. Doing it myself, I understand the risk of getting dust in there, and it not being centered, etc, so... maybe should I just leave as it is?

Where can I get some Vblocks (I guess they are called that?) or prisms to do the centering?

[imagedowser]

See "Protocol For recementing lens elements, by John Schneider, here, on "Lenses and Lens Elements"...

[Marc B.]

This might be one source for some Canada Balsam...when it comes time to re-cement.
I don't have any personal experience/connection with the company, just passing on some info for your project.

Marc

http://www.surplusshed.com/pages/item/b1077.html

Also, a related APUG Thread:

http://www.apug.org/forums/forum85/99375-canadabalsam.html

[Jimi]

Thanks for the information, gentlemen. :)

[Steven Tribe]

Dust and air bubbles are really not a problem. It is possible to check for success before the final "baking". And the two parts can be splilt and cleaned without difficulty and a new attempt made. Use of tooth floss, rather than V blocks is reccommended.
My experience of Aplanats/RRs is that they are quite easy - as long as the lens can be removed from the cell.
If it is just the single lens, I might be able to help you with Canada Balsam - considering you are local!

[cyberjunkie]

See "Protocol For recementing lens elements, by John Schneider, here, on "Lenses and Lens Elements"...

Where is "HERE"?
Not on this forum, i guess, since i have done a search and found nothing.
Maybe it's a book.
BTW, i found a series of four nice books, of which you can find many different editions (second-hand, i i got them from Amazon), which are about making yourself astronomic instruments.
I have the first three books of the series, and there are many paragraphs which are of great interest for the vintage lens enthusiast. In particular there are many infos about lens grinding and cementing.
I confess that i have read only a small part, and that weeding out what's unimportant can be quite tiresome, as most of the stuff is about telescopes and other astronomical matters.
Nevertheless, there are lots of infos that can't be found on other books/Web resources.
The title of the books is:
Amateur Telescope Making by Albert Ingall
There are at least five editions, over a good span of time, and 3 or 4 volumes (i must go by memory now).

have fun

CJ

[imagedowser]

Cyber, Look at the bottom of this page, under "Similar threads"

[cyberjunkie]

Cyber, Look at the bottom of this page, under "Similar threads"

My fault, my fault :(
I made a search, though, and didn't find that thread...

In the meantime i've made another search: browsing through my Amazon purchases, i found that "Amateur Telescope Making" was released in countless editions, i found a fourth edition that was printed during the fourties. There was a later revision, updated and revised, that was published on 1996. I hope that informations about lens work are still there, as most recent books on the same matter concentrate only on mirror making.
The complete set is made of THREE volumes, not four. I was wrong. Some recent ones are titled "Amateur Telescope Making, Advanced". I think it's the second volume.

have fun

CJ

[E. von Hoegh]

I have no idea where to put this, really, but here goes:

I have had the idea (on and off) to recement the rear element of an old brass Rodenstock (it's an Aplanat). It has balsam separation on the edge, and I am thinking of it as a project lens, as the element is very easy to take out. I guess sending it off to a specialist like John at Focal Point would be nice, but the value of the lens (apart from its sentimental value to me) is low. Doing it myself, I understand the risk of getting dust in there, and it not being centered, etc, so... maybe should I just leave as it is?

Where can I get some Vblocks (I guess they are called that?) or prisms to do the centering?

You can find V-blocks at McMaster-Carr.com.

[Kuzano]

My urge to DIY certain things is selective. What you are considering is a NO for me. I just received back a lens from John at Focal Point. Job done excellent, and turnaround quite fast. However, the element(s) that were separating were three pieces of glass. Price was slightly more than the value of the lens in a quick sale market, but I decided to have John repair it.

Sometimes it's not about the money. I don't say that because I have a lot of "scratch". I am retired on a fixed income, and my expenditures are well thought out.

However, sometimes I make a decision based on other factors... one of which is that I decide I just want to see the result of a project. If it works out..great. If it turns out that it doesn't work as I'd hoped, I am prepared for that risk.

When I think of some of the things I have spent money for over the years, the decision I made to fix the lens I already owned was spit in a bucket. I now have a known quantity, as opposed to going into the market and buying another unknown lens. I feel good about that.

Bottom line, what I am saying is, it sounds like this is a bit of an experiment for you on this particular lens, and perhaps the challenge of DIY. However, I endorse Focal Point. The money.... would rather have a qualified repair and get the results I am looking for. Certain pride in that. Your question might be, to yourself, "what do I reasonably expect as results from this lens, with a quality repair at what price?" Second question might be, "Am I OK to lose what image quality I have now if I TFU the recementing?" and last, if my time is money? (an often overlooked question for most for hobby type functions), how much am I actually spending to research the repair, separate and clean the lens elements, gather the tools and equipment, and forge ahead with the repair.

Personally, I can still bill myself out for $50 per hour (nominal... not too low, but below market) doing computer tech'ing as I have for the last 20 years. So, a $300 repair, I can cover in 6 hours of computer work.

So, I'd farm that job out in a heartbeat. Recementing my own lens would be a minimal source of pride, AND it's not likely I am going to go into the business and compete with John at Focal Point.

[Jimi]

Thanks for the further comments and thoughts. Maybe I am doing it the wrong way around, but I am thinking farming it out would cost me $150-200 for the work and maybe another 50 for shipping, and I guess that is why I would be on the fence. If I was to try recementing, I think this lens is as easy as it can get (I don't say it is too easy though, many things can go wrong) - there is a threaded ring that screws out and the lens element is very easily taken out. It's also only two elements.

I would have no qualms about sending the job out if the lens was more valuable or multicoated, me risking wrecking the coating and so on. It's a balance as you say, Kuzano.

[Peter De Smidt]

Give it a shot. You could use a modern UV cure lens cement instead of the Canadian balsam.

[Old-N-Feeble]

Give it a shot. You could use a modern UV cure lens cement instead of the Canadian balsam.

That's precisely what I would do... replace the balsam with UV activated cyanoacrylic glue.

[winterclock]

http://www.popsci.com/archive-viewer?id=PyEDAAAAMBAJ&pg=147&query=lens An old how to on re-cementing lenses. I seem to recall seeing something about re-flowing the cement on delaminated lenses by boiling them, but can't remember where.

[J. Fada]

I have done a few lenses now and it isn't all that difficult. Make sure you mark the lens before you separate the elements. I use a pin to score a line on the edge which works fine and makes it easy to realign the elements. I think you are better off using Balsam instead of the UV glue until you get some experience. I pretty much guarantee that it won't be right the first time you do it. If you use UV cement you will be cursing up a storm trying to get the elements back apart. You will need some small v-blocks. If you soak the elements in Acetone they will eventually separate. I bake the elements with the balsam in the oven for a couple of hours between the v-blocks and then when I take the lens out of the oven I make sure it is aligned and let it cool. I have restored by this method a couple of Computar enlarging lenses which are prone to horrible separation and they are spectacularly sharp now living up to their full potential.

The other down and dirty way is to bake the elements as they are melting the Balsam that is already there. If you get lucky it will fix the problem. If not, no loss. You still need to make sure they are aligned though using v-blocks. If it doesn't work they should come apart easily while the elements are warm

[Steven Tribe]

Stick to Balsam. I gives you the opportunity of doing many attempts without difficulty.
The thread I have on it is labelled:
"How I did it: new balsam for a sick RR".
This is quite extensive.

[imagedowser]

+1 on Steven..... balsam is much easier to reverse.

[Vick Ko]

NO NO NO
Never use cyanoacrylate glue anywhere around optical glass. NASA banned it from their labs.
It creeps and outgasses, and coats all other glass surfaces.

...vick


That's precisely what I would do... replace the balsam with UV activated cyanoacrylic glue.

[John Koehrer]

+1


http://www.popsci.com/archive-viewer?id=PyEDAAAAMBAJ&pg=147&query=lens An old how to on re-cementing lenses. I seem to recall seeing something about re-flowing the cement on delaminated lenses by boiling them, but can't remember where.

I've tried this and it worked pretty easily, lots easier than separating & recementing.
Try it, boiling water isn't that expensive.

[Carsten Wolff]

So that wouldn't work on reasonably new lenses I guess then? When did the big manufacturers change from Canada Balsam (to....)? I have a few 1960 -1970s lenses that may benefit: I just don't want to try it in case modern cements start to bubble, go cloudy, or otherwise make a greater mess when heated....
I did a Canada Balsam replacement on a big old Petzval and that was actually pretty easy. The trick is to use the right amount :) and to center the glass properly. Still looks good after a few years; I sealed the edge about a month after recementing with black laquer to prevent humidity affecting the balsam in the long term. So +3 on Steven.