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PSA: Balm separation repairs chemical warning!
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PostPosted: Sun Oct 01, 2023 6:38 am    Post subject: PSA: Balm separation repairs chemical warning! Reply with quote
Folks, those who like to fix old lenses and especially practicing those with balm separation:

Just a reminder to be cautious about chemical commonly used to separate elements.

It is knowledgeable in our circles that best way to separate elements that started to show "balm separation" is to use paint stripper containing methylene chloride, for example Goof Off paint stripper.
https://en.wikipedia.org/wiki/Dichloromethane

I personally use Goof Off close to ten years and have completed Balm Separation repairs on dozens of lenses. Recognizing how aggressive methylene chloride is - I always did separation and following wash only outside and stored Goof Off only in tightly closed original container in far corner of my garage.

I use two layers of nitrile gloves, and as soon as I feel cold similar to alcohol evaporation on the skin but through the gloves - I change gloves immediately.

Once I got small smudge of Goof Off on my palm, wiped it in two seconst and then got good wash. Years later I still have rough spot on my hand from that exposure. I can only imagine what inhaling that vapor can do to your lungs.

Methylene chloride is nasty, dangerous, deadly chemical that apparently linked to dozens of deaths. According to report by Reuters: "The chemical is linked with lethal brain and liver cancer, as well as non-Hodgkin lymphoma."

Apparently EPA trying to ban consumer sales of anything containing it, some stores voluntarily clearing their inventory.

If you are working on old lenses or using this chemical for anything else, please do your research first and be super cautious with it. I believe warning on these products is not adequate and not perceived by most consumers as it should.


PostPosted: Sun Oct 01, 2023 8:04 am    Post subject: Reply with quote
Your warning is appreciated. I know i got a bit cheeky with chemicals lately.


PostPosted: Sun Oct 01, 2023 8:31 am    Post subject: Reply with quote
Like 1 small Like 1 small


PostPosted: Sun Oct 01, 2023 9:03 am    Post subject: Reply with quote
Like 1


PostPosted: Sun Oct 01, 2023 10:20 am    Post subject: Re: PSA: Balm separation repairs chemical warning! Reply with quote
SalPro wrote:
Folks, those who like to fix old lenses and especially practicing those with balm separation:

Just a reminder to be cautious about chemical commonly used to separate elements.

It is knowledgeable in our circles that best way to separate elements that started to show "balm separation" is to use paint stripper containing methylene chloride, for example Goof Off paint stripper.
https://en.wikipedia.org/wiki/Dichloromethane


You're a bit late ...

Methylene chloride is prohibited in all consumer products - including paint strippers and the like - both in the US as well as in European countries for many years now (dunno about Ukraine, Russia, and China though). Probably your own "Goof Off" is many years old, as nowadays the "Goof Off" paint strippers do NOT contain methylene chloride any more (I just have been checking the data sheets). Usually it was replaced by a mix of non-chlorinated solvents including acetone.

Acetone is well suited for cleaning lenses, as long as the parts are made of glass and metal (some colors may come off). It has a low toxicity, but it "opens up" the skin allowing other pollutants to enter more easily. BTW acetone naturally is the main organis substance found in our exhaled air!!

Another even less problematic substance is propanol and iso-propanol (often used as a disinfectant as well). Works well for cleaning threads, for example, or for removing dirt from the outside of lenses.

Yes, I have studied chemistry, and I've worked for years in the chemistry/physics border zone (ion traps and mass spectrometry), thus I'm well aware of the potential damage caused by methylene chloride.

S


PostPosted: Sun Oct 01, 2023 10:37 am    Post subject: Reply with quote
In the EU methylene chloride (DCM, dichloromethane) has been banned for sale to the general public for some years now (since 2010).
Even paint-stripper for sale to the general public can no longer contain DCM.

It is still available for sale to professionals, but only upon registering details re. the profession and company registration number, as well as documented evidence of training in handling & disposal.

I recently saw a 2.5 litre dented metal container of the stuff available on eBay (an illegal listing for sure); tempting, but having read up on the health hazards I do not want to have 2.5 litres of DCM sitting in my garage in a dented rusty metal container, or one day I walk into my garage and never walk out.

Longer-term storage in plastic containers is prohibited on account of the aggressiveness of this solvent (even HDPE and PP are not completely resistant to it as far as I understand). It is sold in plastic containers but needs to be decanted into glass or suitable metal containers as soon as possible after purchase.

Even handling a sufficient quantity without wearing gloves can cause enough of it to be absorbed through the skin that the person may die of carbon monoxide poisoning (DCM in the body metabolises to carbon monoxide). Normal household gloves are completely inadequate; DCM goes straight through that.

So yes, separating UV-cured epoxy-cemented lenses has become close to impossible. Canada balsam also has its drawbacks but it is far more convenient should repair/re-cementing be required.

For Canada-balsam cemented lenses DCM is not required at all; slowly heating will usually soften the balsam enough for separation; the older (harder) the balsam, the higher the temperature required. If it is very old, a prolonged soak of the doublet in acetone, isopropyl alcohol, or xylene will also do the trick.
The hardness of the balsam depends on the percentage of volatile terpentines still contained in the rosin; with time these will evaporate and very slowly the balsam will become harder, until eventually it fails under thermal expansion/contraction of the elements (which may look like crystallisation, but the rosin never really truly crystallises)

Anyone interested in the practical technical process of cementing elements with Canada balsam, including the preparation of the appropriate hardness of the balsam itself, I would recommend to read "Prism And Lens Making", F. Twyman, second edition, CRC press, 1952, pages 238-250, which was re-printed in hardback in 2017.
Anyone interested in the state-of-the-art techniques of optics manufacturing in the early 1950's should find this a very interesting book. Whilst dated, much of the techniques described re. grinding, centering, polishing, collimation, curvature measurement, etc. still apply today.


PostPosted: Sun Oct 01, 2023 11:38 am    Post subject: Reply with quote
RokkorDoctor wrote:

...
I recently saw a 2.5 litre dented metal container of the stuff available on eBay (an illegal listing for sure); tempting, but having read up on the health hazards I do not want to have 2.5 litres of DCM sitting in my garage in a dented rusty metal container, or one day I walk into my garage and never walk out.

The stuff is pretty smelly. No way you'd die before noticing it. But of course keeping it in rusty container is not a good idea.

RokkorDoctor wrote:
Even handling a sufficient quantity without wearing gloves can cause enough of it to be absorbed through the skin that the person may die of carbon monoxide poisoning (DCM in the body metabolises to carbon monoxide).

Well, sufficient quantities of ethanol or NaCl will kill you as well. Methzylene chloride is not highly toxic at all (it was used in endless quantities as a "good solvent" in the labs until about 1980), but long-term exposure may cause cancer.

RokkorDoctor wrote:
Normal household gloves are completely inadequate; DCM goes straight through that.

Correct.

RokkorDoctor wrote:
So yes, separating UV-cured epoxy-cemented lenses has become close to impossible.

Not correct. I recently did separate an epoxy-cured doublet without using dichloromethane. More on that later on.

S

PS there are also commercially available Epoxy-removers, based e. g. on Dioxalane and Methylal.


PostPosted: Sun Oct 01, 2023 2:21 pm    Post subject: Reply with quote
stevemark wrote:
I recently did separate an epoxy-cured doublet without using dichloromethane. More on that later on.

S

PS there are also commercially available Epoxy-removers, based e. g. on Dioxalane and Methylal.


I would love to know how you separated it; I have a doublet of a Bronica PS lens that needs separating, and everything has failed so far. The only thing I haven't tried yet is the Norland-suggested method of heating it to 200 degree centigrade for at least an hour, but the crown is really thin and I'm afraid of accidentally cracking it.


PostPosted: Sun Oct 01, 2023 4:07 pm    Post subject: Reply with quote
RokkorDoctor wrote:
stevemark wrote:
I recently did separate an epoxy-cured doublet without using dichloromethane. More on that later on.

S

PS there are also commercially available Epoxy-removers, based e. g. on Dioxalane and Methylal.


I would love to know how you separated it; I have a doublet of a Bronica PS lens that needs separating, and everything has failed so far. The only thing I haven't tried yet is the Norland-suggested method of heating it to 200 degree centigrade for at least an hour, but the crown is really thin and I'm afraid of accidentally cracking it.


There are specific expoxy-specific solvents. There used to be a specialized website...


PostPosted: Sun Oct 01, 2023 4:26 pm    Post subject: Reply with quote
RokkorDoctor wrote:

I would love to know how you separated it; I have a doublet of a Bronica PS lens that needs separating, and everything has failed so far. The only thing I haven't tried yet is the Norland-suggested method of heating it to 200 degree centigrade for at least an hour, but the crown is really thin and I'm afraid of accidentally cracking it.


I actually have been heating the (small) doublet, but in a gradual way using an IR source. After estimated ten short bursts using an 1 kW IR source within 2-3 min I was able to separate the two lenses. The smell clearly was indicating "epoxy", and not "canada balm" at all ... thus confirming what I had read before about the "unrepairable" Sigma lenses (i. e. that they were epoxy-glued).

To remove the remaining resin the still warm (but not hot!) lenses were soaked in acetone which allowed me to clean them. Not perfect (would have required another heating I guess), but rather useable.

For time being I have re-assembled the Sigma zoom without re-glueing the lenses, and thus perfomance certauinly isn't "as new", but - of cours - way better than before cleaning/separating hte doublet.

Hope that helps ...

S

BTW I chose (indirekt) IR heating over conventional (direct contact) heating because I assumed the radiation would mainly be absorbed by the epoxy resin, and not by the glass, thus reducing the risk of thermal stress and destruction. Not sure if that theory is correct, though ...

BTW II: the heatened epoxy stuff may be a bit hazardous, thus wearing gloves probably makes sense.

PS Next lens may be one of the Sigma 5.6/400 APO teles I have ...


PostPosted: Sun Oct 01, 2023 4:39 pm    Post subject: Reply with quote
For military: Milbond Adhesive System / Milsolve Decementing Agent https://www.edmundoptics.com/f/milbond-adhesive-system-de2e7253/11386/ https://www.edmundoptics.com/f/milsolve-decementing-agent-c38bcb31/14093/

The Bonding of Optical Elements - Techniques and Troubleshooting http://web.archive.org/web/20070220153603/http://www.emsdiasum.com/summers/optical/cements/manual/manual.html

Welcome to the Summers Optical Homepage https://www.optical-cement.com/

Optical Adhesives https://www.edmundoptics.com/c/adhesives/644/#

Optical Cements and Adhesives - Photonics Marketplace https://www.photonics.com/Buyers_Guide/Optical_Cements_and_Adhesives/ca15800


PostPosted: Sun Oct 01, 2023 4:49 pm    Post subject: Re: PSA: Balm separation repairs chemical warning! Reply with quote
stevemark wrote:

You're a bit late ...

Methylene chloride is prohibited in all consumer products - including paint strippers and the like - both in the US as well as in European countries for many years now


Yes but no. US was and still way behind the rest of the world banning it. Somebody creative with search still can find some to buy. Here is the article that got me going:
https://autos.yahoo.com/us-sues-ebay-allowing-sale-183000343.html
Forget about coal driving, read the middle. So, everybody not automatically safe nowadays. Somebody can read old threads and become creative finding way to acquire Dichloromethane. This is a warning first of all for these people. Apparently even today you may find it on US Amazon. Often there is no problem to ship worldwide. For example I shop some stuff on Euro Amazon for stuff that is not available in US. Amazon does not filter restrictions on MSDS vs. local law. The only restriction or rather barrier is shipping cost. Some customs, like German, maybe more methodical about checking content of the parcels, but most are relatively transparent.

My bottle of Goof Off is dated when I just tried balm separation first time, almost 10 years ago. Maybe half liter metal flask. Over all those years I use maybe 5% of it. I have no plans to get rid of it, but I will crank up my precautions when using it. Maybe I have to acquire exhaust hood/cabinet, or use additional fan outside.
Sad/fun fact: it came with plastic spray bottle!

To separate group, epoxy or Canadian rosin/balm bonded, unfortunate there is no practical alternative I can find. I had marinated glass in pretty much anything that considered to be a solvent, for months. Nothing works but DCM. The most ever it took to separate elements is 5 days, some as fast as 2 hours. I had Leica lens from 1920 that was abandoned because front element looked like sandblasted. No common cleaning method worked, even acetone. So I dunk it into DCM. Turned out it was some organic stuff on the surface, that cleaned beautifully and glass was actually pristine. I do not see alternative to DCM. I would not try to heat to 200C. I think stress in the glass can cause problems before usable results, maybe even glass distortions that may degrade optical performance.

But I got too far into what should be separate thread.

Please be safe if using Dichloromethane, or just avoid it.


PostPosted: Sun Oct 01, 2023 5:12 pm    Post subject: Reply with quote
visualopsins wrote:


Not being fancy, once I've tried super cheap LOCA sold for phones/LCD repairs, I no longer have to spend what sold as specialized optical lens glue as balm alternative.
It can be cured with sun light, or you may construct light source of appropriate wavelength, you can find right LED on Ali/Ebay. (EPROM eraser UV light does not work for LOCA, need very specific wavelenght).

I've studied my results with LOCA very carefully, I had couple restored lenses that I had chance to compare vs. originals, and in every case lenses restored with LOCA glue had better index matching/lesser internal reflections of the doublet, than originals, essentially become brighter.

Again, if balm separation is hot topic here - maybe we should start separate thread to share best practices?


PostPosted: Sun Oct 01, 2023 5:24 pm    Post subject: Re: PSA: Balm separation repairs chemical warning! Reply with quote
SalPro wrote:

Please be safe if using Dichloromethane, or just avoid it.


Occasional use in a well ventilated place certainly is no problem at all.

MAK (German abbrievation for "maximum allowed concentration at worling place") is 0.185 g / m3 air - eqivalent to 33g (or one ounce) in my current living room. That's a lot. And you'd be officially allowed to breath that all day long, every day.

"Derived no effect level" for skin contact is about 5 g per day (for long-term damages, that is. Level for acute damage would be considerably higher).

S


PostPosted: Sun Oct 01, 2023 6:37 pm    Post subject: Reply with quote
stevemark wrote:
I actually have been heating the (small) doublet, but in a gradual way using an IR source. After estimated ten short bursts using an 1 kW IR source within 2-3 min I was able to separate the two lenses. The smell clearly was indicating "epoxy", and not "canada balm" at all ... thus confirming what I had read before about the "unrepairable" Sigma lenses (i. e. that they were epoxy-glued).

To remove the remaining resin the still warm (but not hot!) lenses were soaked in acetone which allowed me to clean them. Not perfect (would have required another heating I guess), but rather useable.

For time being I have re-assembled the Sigma zoom without re-glueing the lenses, and thus perfomance certauinly isn't "as new", but - of cours - way better than before cleaning/separating hte doublet.

Hope that helps ...

S

BTW I chose (indirekt) IR heating over conventional (direct contact) heating because I assumed the radiation would mainly be absorbed by the epoxy resin, and not by the glass, thus reducing the risk of thermal stress and destruction. Not sure if that theory is correct, though ...

BTW II: the heatened epoxy stuff may be a bit hazardous, thus wearing gloves probably makes sense.

PS Next lens may be one of the Sigma 5.6/400 APO teles I have ...


Thanks for the info, I may have a go; Norland advise heating it slowly in a bath of mineral oil, I don't have a suitable IR source. My worry is that no matter how slowly and carefully I heat it, the differential rate of expansion between the flint and crown is enough to crack the very thin crown before the cement becomes sufficiently soft to allow for creep.

Not much to lose really anyway; the doublet is completely unusable as it stands. It looks like the cement has gone slightly opaque, from what I have read this can happen if the cement was contaminated in the factory.

What I find curious is that someone else had the same problem with the exact same doublet of the exact same model Bronica PS 35mm FishEye lens. My late copy of this lens would have been manufactured a few years after Tamron acquired Bronica, just before they discontinued the Bronica SLRs; I have personally never heard of or experienced a similar problem with older (pre-Tamron) Bronica PS lenses, which may just be a coincidence.


PostPosted: Sun Oct 01, 2023 6:44 pm    Post subject: Reply with quote
RokkorDoctor wrote:

Thanks for the info, I may have a go; Norland advise heating it slowly in a bath of mineral oil, I don't have a suitable IR source. My worry is that no matter how slowly and carefully I heat it, the differential rate of expansion between the flint and crown is enough to crack the very thin crown before the cement becomes sufficiently soft to allow for creep.

Not much to lose really anyway; the doublet is completely unusable as it stands. It looks like the cement has gone slightly opaque, from what I have read this can happen if the cement was contaminated in the factory.


I haven't done much research into this, but I have access to methylene chloride since I am a fully qualified chemist. If you want you can sent me the doublet and I'll soak it. If it doesn't work you still can use heat & (slight) force.

PM me if you're interested.

S


PostPosted: Mon Oct 02, 2023 10:14 am    Post subject: Reply with quote
stevemark wrote:
RokkorDoctor wrote:

Thanks for the info, I may have a go; Norland advise heating it slowly in a bath of mineral oil, I don't have a suitable IR source. My worry is that no matter how slowly and carefully I heat it, the differential rate of expansion between the flint and crown is enough to crack the very thin crown before the cement becomes sufficiently soft to allow for creep.

Not much to lose really anyway; the doublet is completely unusable as it stands. It looks like the cement has gone slightly opaque, from what I have read this can happen if the cement was contaminated in the factory.


I haven't done much research into this, but I have access to methylene chloride since I am a fully qualified chemist. If you want you can sent me the doublet and I'll soak it. If it doesn't work you still can use heat & (slight) force.

PM me if you're interested.

S


Thanks for the offer Stephan, but there is another doublet in that same lens that is developing the same issue. I think I have to bite the bullet and try the heating method, so I have a new technique mastered for whenever I need to separate epoxy-cemented lenses. Experimenting is part of the fun and whilst not exactly common, that lens is not particularly rare or valuable.

I will use another modern scrap-lens to practice on first, to see how well it works, although I assume there is no guarantee that what works for one epoxy works equally well for another.


PostPosted: Mon Oct 02, 2023 11:01 am    Post subject: Reply with quote
There is probably an answer I'm missing by not reading the appropriate sources first, but are the anti-reflective coatings on the front and rear of a doublet effected by the process? Submerging in water and boiling etc.

I know the temperatures required to coat a lens are at least double of 200c, but still.


PostPosted: Mon Oct 02, 2023 12:53 pm    Post subject: Reply with quote
eggplant wrote:
There is probably an answer I'm missing by not reading the appropriate sources first, but are the anti-reflective coatings on the front and rear of a doublet effected by the process? Submerging in water and boiling etc.

I know the temperatures required to coat a lens are at least double of 200c, but still.


You are a more talented man than I am (or one with an autoclave) if you manage to heat something to 200c by boiling it in water. Thats why mineral oil was suggested Wink

They are modern vacuum-deposited hard coatings and shouldn't be affected. I'm not sure about the effect on the latest oleophobic coatings, which might well be damaged, but those haven't been applied to the doublet I am looking at.


PostPosted: Mon Oct 02, 2023 1:32 pm    Post subject: Reply with quote
Hah, sorry, vague memory is no excuse for that basic oversight of mechanics... Embarassed

What I may have been misremembering is people putting it in the oven to separate.


PostPosted: Mon Oct 02, 2023 4:38 pm    Post subject: Reply with quote
At least as you use "normal" optical glass there's no need to coat the cemented surfaces of doublet. I fact canada balsam was chosen for cementing lenses precisely because of its relatively high refractive index of 1.52 - 1.55.

I have no idea whether the cemented surfaces of a doublet might be coated for other reason though. The Sigma doublet I have been separating was not coated at the inside, and the cooating of the outside surfaces remained intact. As I said, I had been heating the doublet with IR though, thus keeping the temperature of the glass relatively low - and the glass was not immersed in oil of course.

S


PostPosted: Mon Oct 02, 2023 6:33 pm    Post subject: Reply with quote
It is not so prohibited that I cannot order it easily online:



PostPosted: Mon Oct 02, 2023 6:52 pm    Post subject: Reply with quote
D1N0 wrote:
It is not so prohibited that I cannot order it easily online:



There are a few places I can order it here in the UK as well. Unfortunately, whilst you can order it on-line, they won't actually send it out until you prove your status as a professional user and fill in a declaration of use form.

Unless the seller you found is breaking the law, they'll have to do the same. I would hazard a guess that unless you can prove the correct professional credentials after ordering, they would refund you and cancel the order.


PostPosted: Mon Oct 02, 2023 7:12 pm    Post subject: Reply with quote
D1N0 wrote:
It is not so prohibited that I cannot order it easily online:


You can try to order anything for sure:
https://www.lipomed-usa.com/en/halluzinogene

Would you get it? Probably not.

S


PostPosted: Mon Oct 02, 2023 7:27 pm    Post subject: Reply with quote
stevemark wrote:
D1N0 wrote:
It is not so prohibited that I cannot order it easily online:


You can try to order anything for sure:
https://www.lipomed-usa.com/en/halluzinogene

Would you get it? Probably not.

S


Why go online when I can just go to a local smart shop: https://www.google.com/search?client=firefox-b-d&q=smart+shop+groningen Or visit the woods with a mushroom almanac :p
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