Uv glue for lens repair

[clie]

Steve

I'm planning to use UV glue on a Canon FL 58/1.2, this is my first attempt.
Can't find Canadian Balsam here in Australia so I managed to get 'Original Superglue' branded UV glass glue.
How many drops should I use? I read in different post ranging from 2 drops to 8 drops.
I'm also worried about how to get rid of lens bubbles?
Any tips from your experience will be great. Thanks

[Steven Tribe]

There is a better thread on recementing lenses.

No Canada Balsam manufacturers in Denmark either, but it is easy to get hold of through the internet. I have bought through different suppliers - always OK product. Do not buy the yellow solids for use with solvents.

2 drops (size?) sounds too little and 8 drops too much. Obvious a big Petzval uses more than tiny lenses.

[clie]

Hi Steve

I've managed to work out how much glue. I used Vegetable oil as a dry run as someone said it has the same consistency as Canadian Balsam. After several trials with veg oil, I gained enough confidence about how much glue to use. Then on the final step, I put a little more UV glue than I thought is needed, and when I put the two lens together, the glue filled the entire lens in less then 5 secs. Also, no bubbles either. The UV glue is great because it gave me about 30 mins to position the two lens before it started to firm up.
Now I just hope the UV glue last as it is a named brand that I bought from a large hardware store.

[Steven Tribe]

Well done!

Sounds like a very sensible "dry" run system.

I have just done a recementing job to-day on a big Suter Anastigmat (copy of the Dragor) with 4 lens in each cell. So first glass 1 & 2 are joined, then 3 & 4 and finally 12 is joined to 34! So lots can go wrong and you have to have concave surfaces to act as a balsam/UVcement reservoir. There are lens which have 5 components glued together.

[clie]

Wow. What a complex lens to reglue Also alignment of 4 lens will be a nightmare. Luckily you're an old experienced hand

[Drew Wiley]

See if Edmund Scientific will ship there, or has an outlet. They have all the right stuff.

[Nodda Duma]

Norland 63 is the most common UV optical adhesive for bonding doublets (at least in my experience). It is good for -15 to 60 C and retains a slight flexibility when fully cured (important for temperature shock). It transmits over a large spectral band and the optical properties are well understood. I've never seen a debond occur with this stuff.


But really the more important point for maintaining good bond over time is matching the thermal expansion coefficients of the crown & flint. If they differ too widely then the adhesion will eventually fail if the lenses are exposed to the real world.

[Steven Tribe]

But really the more important point for maintaining good bond over time is matching the thermal expansion coefficients of the crown & flint. If they differ too widely then the adhesion will eventually fail if the lenses are exposed to the real world.

Which is why a couple of modern lenses I have posted, just fell apart during shipment.

Balsam, which is not in contact with air, maintains a certain degree of liquid character through the centuries. Experience with synthetics is still limited to 60 plus years!

Also alignment of 4 lens will be a nightmare.

Not really! Makers did think about assembly techniques - and mounting techniques - so that they didn't make things more difficult than necessary for their staff. The biggest problem for lens overhaul is often mounting systems, where the possibility that the glass should be removable for servicing, without a lathe, didn't occur to many renown makers (D***m***r included).

[Nodda Duma]

Which is why a couple of modern lenses I have posted, just fell apart during shipment.

Balsam, which is not in contact with air, maintains a certain degree of liquid character through the centuries. Experience with synthetics is still limited to 60 plus years!

The Balsam bond joint in older lenses will fail for the same reason. The Contaflex (35mm format) wide angle Tessar attachment has a failure mode due to this for example...it is bonded with Canada balsam. Sometimes you'll come across WW2-era US Navy binoculars with a debonded objective doublet.

I've repaired a fair amount of old cemented doublets which had failed on the (Canada balsam) bond line.

Balsam is like pitch: flows slowly but is brittle. Stress and temperature shock will cause a failure. Most modern UV adhesives don't have this issue. That said they both have their place.

I kind of wonder if there may have been a manufacturing or design flaw there in your lenses...either improper cure or a gross oversight by the design team...or the lens being used outside it's intended temperature range. Since we don't know how the lens was assembled we can only speculate on the cause.

Interestingly enough, I have seen one assembly fail in the past not at the bond joint, but the actual glass failing and breaking near a bond line under extreme temperature testing. The bond stayed intact, but the stress in the glass caused a failure with an audible pop which left behind a thin layer of the flint bonded to the crown. I don't remember exactly what the adhesive was but it wasn't Canada balsam. It was pretty cool.

Interesting article on adhesives:

http://fp.optics.arizona.edu/optomec...sTutorial1.doc

The article is written by a student but it regurgitates info from people like Yoder, Vukobratovich, and Karow.

[John Schneider]

If you just tack it in place (45 seconds or minute or so of UV from a CF bulb) it isn't that hard to get it apart if you check it out and decide you are off center. Unless this cheap cement cures in the sunlight range, in which case it takes sunlight or a sun lamp.

I have never used balsam, but the UV cure cement from Summers has worked well for me.

It is hard to get right the first time. Or the second, or third. But once you get the hang of it this isn't that hard. Cleanliness is everything before applying
cement. Use really clean fresh acetone to get the lenses surfaces clean.

I have had good experience using Summers Optical products (type J-91 adhesive in particular) for jobs up to and including a 19" Dagor: https://www.optical-cement.com/cements/chart.html

Like Kevin said, your first time or two you won't be satisfied and you'll separate the elements and clean everything with acetone again, and then try cementing again. Being a UV-cured adhesive, it's easy to undo until cured.

I have not used Canadian balsam at all but this is probably a good source (based on my other dealings with them): http://www.surplusshed.com/pages/item/b1077.html

I've seen too many WWII binoculars with debonded prisms (British Barr & Stroud models seen to have a particularly hard go of it, perhaps because of their porro-2 construction) to want to try balsam (but YMMV).