Breaking the baffling B & L Balplan buffalo.

[BramHuntingNematodes]

Dissolving the existing optical cement in the ef lens assembly that has milked over, as described above.

[Hobbyst46]

Assuming that the previous optical cement is Canada Balsam, there are several potential solvents: benzene, chloroform, xylene, ether and ethanol are mentioned. In a lab, any of them can be tried, given a fume hood and protective equipment, but I believe that chloroform and xylene are especially potent (IMHO). Xylene is less volatile, not as heavy as chloroform and easier to use. Ether, as well as methylene chloride, might evaporate too rapidly to leave any residue that penetrates between the lenses and dissolves the cement.

For home use, I would try xylene, in an aerated space, and using minimum quantity. Benzene, ether, chloroform should be avoided in hobby use. Ethanol is - I think - less potent than the others.

I do not know if dimethyl sulfoxide or carbonate dissolves balsam. Note, that the sulfoxide freezes at ~13C and is quite viscous at room temperatures. Don gloves if trying - it penetrates into the skin.

[BramHuntingNematodes]

Very int we eating, thank tou.! It sounds like there are a few options. I even found some older Bix paint stripper hat is mostly methylene chloride. I don't know if it is balsam. The scope is from the 1960s or 70s and the delamination pattern is not the same as a characteristic balsam delamination I have on an ancient objective.

I don't have much experience with coated optics as most of my equipment is very old. This 60s scope is pretty Hi-Tech and new fangled! Are the coatings as good as gone if I use these chemical solvents ?

[Hobbyst46]

Very int we eating, thank tou.! It sounds like there are a few options. I even found some older Bix paint stripper hat is mostly methylene chloride. I don't know if it is balsam. The scope is from the 1960s or 70s and the delamination pattern is not the same as a characteristic balsam delamination I have on an ancient objective.

I don't have much experience with coated optics as most of my equipment is very old. This 60s scope is pretty Hi-Tech and new fangled! Are the coatings as good as gone if I use these chemical solvents ?

I believe that even old coatings are resistant against solvents, but, in the case I am wrong, then from this aspect too, xylene is better than dimethyl sulfoxide or carbonate.

[wporter]

No, coatings from the 60's should be immune to any of those solvents, being primarily magnesium fluoride.

(As for modern multicoatings such as are found on camera lenses, the types of coatings differ, so opinions and results differ, so it's best not to chance certain solvents on those. However, it's hard to imagine one of these coatings would be damaged by an alcohol, for instance, since those can be a component of most common lens cleaners)

[apochronaut]

I doubt if the cement is balsam. B & L used a synthetic cement of some type for at least some of the production from the Dyna era. All of the de-lamination I have seen has fairly consistent breakdown characteristics, similar to some of the characteristics of balsam , yet not the same. The cement is immune to ethanol.
I have used heat and mild pressure to some effect with doublets. Part of the problem is due to changes in the physical properties of the polymer but some may also be due to disadherence, so there is also physical separation.

I made up a jig, using a medication bottle and some pieces of precision cut wine cork. The compressible plastic cap liner that makes the bottle seal when locked, provides enough but not over pressure on the lens elements. Sealing the optic inside the medication bottle, stops it from being buffeted and disturbed , if the water starts to bubble.
Cut two separate wine cork surfaces to conform to the surfaces of the top and bottom of the optic to be repaired. Cut the other end of each cork , so that the optic can be suspended in the center of the bottle and when the bottle is closed the cap is quite difficult to lock, kerping a small pressure on the optic. The bottom surface of the bottom cork will need a relief , big enough to hold the rounded button that many such bottles contain on the bottom. It will take a few corks and a few tries to get it right. Fill the bottle with water.
Place submersed in s small saucepan and hold at 170 -180 for 1/2 hour or so. I have had success with several and several too, maintained a slight swirl of a hazy quality. I didn't retry the failed ones.
I have separated one really bad one in this fasion and found that the cement came from the glass quite cleanly.

[BramHuntingNematodes]

Thanks all! These are excellent and edifying comments. Since it seems that there is little danger of dissolving the coatings, I have put the assembly in some methylene chloride/ tuluene/ methanol paint stripper for overnight after scribbling some pencil lines on the side. If that doesn't work, I am advising my partner to retain wine corks for Apo's method. While some chemicals seem to be embarrassed of their poisonous nature, not so with methylene chloride. It smells unmistakably like death and confusion. It's outside in the shed in a loosely capped jam jar (jam was removed earlier).

The delamination looks different from balsam, which always to me looks like the old 80s Nickelodeon logo ala:




The doublet was difficult to photograph, but looked more like a bleary milk with spots:

[BramHuntingNematodes]

And sorry if this got a little off-topic. The Dynazoom is an intriguing ancestor to the Balplan, and maybe some documentaion about B&L cement failures of the earlier area might be useful to someone.

[apochronaut]

Synthetic cements became necessary but not common after the war, as the inadequacy of balsam's shock, humidity and solvent resistance became glaring. The military spearheaded research into alternatives. The first in the 40's were two part polyster compounds; resin and hardener, followed by uv cured polyster and urethane types in the 60's.
The cement failures with these scopes are in groups. The second doublet in the 20X planachros for instance. You get a foggy 20X planachro and it will always be that doublet. The first in the 100X iris planachromats.
Lens elements are made in batches, so obviously something went wrong with a certain batch of cement used to make the batch. If I had to hazard a guess, I would put the finger on some material used in the dispensing devices. A silicon lubricant or perhaps some other lubricant that made it's way into the cement and eventually reacted enough with it over time to cause hazing, crystallization or even gas bubbles. Perhaps even certain wavelengths of light exacerbated the process.

This is the first time I have seen it in one of the telescope lenses, though but I haven't been around too many of those Dyna flat field heads. I.Miller probably has a new lens in stock still, since they bought up a lot of B & L's surplus at the dissolution of B & L by Leica.

[BramHuntingNematodes]

I have certainly been "buffaloed" by this lens! Over the last week I have tried soaking for 24 hours in isopropyl, lacquer thinner, acetone, xylene, methylene chloride in both Bix paint stripper and a new bottle of "Attack" epoxy solvent, thermal shocks in each of these as described on the Norland site around the 12-hour mark, and in each of these, slight shear pressure was differentially applied to the two elements using a small spring clamp. I used Apo's Lens Boiling Apparatus (ALBA) twice, for 30 minutes then later for one hour. The only progress I have made is that the lens is now cloudier than before.

I was disappointed by Microscope Central's customer service on two occasions, after putting in a formal request, emailing, then later chatting I have only received a "we're busy and don't have the time to either look for it or even give you a quote you requested on an item listed publically on our website." Sheesh!

Ebay has some heads from Dynazoom models, and while I thought most parts were the same across the Flat Field and non-Flat Field model, the ones I see are missing the cylindrical element I am trying to fix entirely.

So...the last thing I can think of would be to heat the lens assembly to much higher temperatures, perhaps 350-400 F, in an oil bath. Does anyone have any tips for this? I believe I am supposed to let the assembly cool slowly while still in the oil. My plan was to to turn off the oven and walk away for a few hours.

[Hobbyst46]

Unless the oil is silicone oil, it is probably inflammable. So, not to be overheated.
Are you sure that the cloudiness is not between the two glued glass elements ? if so, perhaps the cement has been penetrated by any of the solvents.
As a possible alternative to the messy hot oil, why not try a heat gun ? I mean, the hair-drier-like machines that produce very high (but regulated) temperatures that can weld plastics.
They easily reach 400F and much higher.

[BramHuntingNematodes]

The cloudiness is definitely between the elements. I have a heat gun, but am wary to use it if it might damage the lens-- the oil has some more thermal inertia. Does anyone have experience with heat guns for lens separation?

[MicroBob]

The fact that the lens group got cloudier in the process tends to tell that it is the cement layer that causes the problem, and this is good. Nearly all glues become soft or disintegrate between 100-200 °C. So I would heat with a heat gun as Hobbys-doron suggested and prepare myself to twist the hot lenses apart immediately. Ordinary leather gloves (minus the angle grinder dirt) will do. Once the solvents can attack the whole surface it will be much easier to revove the glue residues. Depending on the lens shapes It would be an idea to mark the orientation by scribing at the border with a file or tungsten carbide scriber.

BTW: I just bought an B&L Dyna Zoom, albeit a simple one than yours. It is probably one of ten in Germany since we have nearly no amaerican microscopes here.

Bob

[BramHuntingNematodes]

OK. Then I shall steel myself and blast away.

[wporter]

While you could use your hands to push the hot glass lens elements apart, what I did once, successfully, was to place a spring clamp diagonally across the corners of the two elements to get a shearing force, then submerged the whole thing in water to boil slowly (although I suppose you could use any solvent that wouldn't dissolve your clamp). Nothing happened right away during the boil, but as it was cooling, I came back a few hours later and the two elements had slid apart; whatever they had used as cement was very tenacious. As I recall, the cleanup was done relatively easily with xylene, although soaking it for three days in xylene hadn't worked, oddly enough.

[apochronaut]

Although I have not attempted to repair that doublet as old as yours from B & L, some were pretty close. The repairs using a hot water bath were 50/50, with a couple excellent and a couple of failures, developing a cloudiness as you noted. It does indicate that there is some degree of water invasion into the cement. One would think it had a natural origin? In the cases where the repair tactic failed though, the cement became pliable enough at only the boiling point maximum, for the elements to separate and then the cement easily peeled off.
It is possible that B & L used more than one cement over the years. You mentioned a whole string of solvents you have tried but you did not mention 100% ethanol?

At any rate; it seems like an awful lot of effort. Have you phoned Microscope Central and asked to talk to one of the senior Millers? I believe there may be 3 generations there still. Mike would be the one to talk to. Harvey, may have retired or be in only intermittently. He was there when the B & L lines were a happening thing but I think Mike was as well. His son, Sean I believe is his name, was not. I'll bet they have that lens. You will possibly need to quote the part # 311959-073.

Other option as you mentioned is a lens from a derelict head. Any of these look promising?

https://www.ebay.com/itm/B-L-Bausch-Lom ... Swqc5c7uiV
https://www.ebay.com/itm/BAUSCH-LOMB-BI ... SwsIBdRDNW
https://www.ebay.com/itm/Bausch-amp-Lom ... Sw0UdXwJkV
https://www.ebay.com/itm/BAUSCH-LOMB-MI ... e2715322d8
https:/

[BramHuntingNematodes]

Thanks Apo, you're support and expertise is appreciated. After having looked at eBay for some time at these old heads I think perhaps the lens I am looknig for is the part # 311811-028 AB assy. Here is where it's at:





I should hope they do have this lens, as I believe I must have well and truly destroyed this one. It may be the entire head is now junk. In addition to haziness, it looks like the inner meniscus surface of the lens is made of frosted glass? and was coated in some material, which has now half fallen apart (even as the glue that binds the elements holds tight).

From top:


from bottom:


Pretty sure it really is two peices:


The frosted surface:



I have never heard of this type of construction before. I hope I have not destroyed this old scope after a single tantalizing look through its 10x!

Perhaps I should give central a call. I don't know how delicate the collimation process is as mentioned in the manual. Maybe it's impossible. Anyway, this has been a somewhat dispiriting misadventure-- probably should have just looked for a Balplan!

[apochronaut]

Not frosted glass. It is utilized as a common rear lens for all the objectives. I think above it there is possibly a further lens, that is a magnifier? I don't know the Dyna Flat Field scopes as well as the Balplan but in the Balplan, the lens was redesigned into one unit. Why would you think that the rest of the head is now damaged?

[BramHuntingNematodes]

The rest of the head seems to be in perfect condition, but none of its objectives will work without this lens, right? There is a rough texture to this lens, and the gunk on the back is on the exterior. It's strange to me. The common rear element! That's why it's not on any of the non flat-field heads-- would it be on a flat field Dynoptic?

[BramHuntingNematodes]

On a positive note, I did find the last ball bearing!

[apochronaut]

The rest of the head seems to be in perfect condition, but none of its objectives will work without this lens, right? There is a rough texture to this lens, and the gunk on the back is on the exterior. It's strange to me. The common rear element! That's why it's not on any of the non flat-field heads-- would it be on a flat field Dynoptic?

Without it, and if you also remove the CF lens assembly; you have a head for the 160mm Dynoptic/Dynazoom. Yes, the same telescope lens assemblies are in the non-zoom version.

[BramHuntingNematodes]

The rest of the head seems to be in perfect condition, but none of its objectives will work without this lens, right? There is a rough texture to this lens, and the gunk on the back is on the exterior. It's strange to me. The common rear element! That's why it's not on any of the non flat-field heads-- would it be on a flat field Dynoptic?

Without it, and if you also remove the CF lens assembly; you have a head for the 160mm Dynoptic/Dynazoom. Yes, the same telescope lens assemblies are in the non-zoom version.

I have been denied three times by I.Miller, alas! They would sell me a head for $250, but not a lens. I suppose I can't expect too much for the penny ante I am bringing to the table.

Another perhaps insane question: as there seem to be several sad Balplan corpses going for less than $100 at the auctions, is it possible that one of these might contain the rear element lens that is compatible with (i.e. could be put into) the flat field Dynazoom? The diameter of the DZ lens is, as near as I can tell, 7/16ths of an inch. I would look elsewhere for information after having already asked so much, but this is a question probably only a small handful of people in the entire world could legitimately speculate on, maybe only a slightly larger handful have ever been able to.

[apochronaut]

Miller are foolish about parts. They are always shooting for top dollar. I don't think the Balplan set up for that optic is the same. I will look for sure tomorrow.

I am curious why you do not consider any of the heads or complete stands that I sent links to? Most were quite cheap.. Did you try dropping that lens in 100% ethanol?

[BramHuntingNematodes]

One of the stands might be a flat field, but the heads don't appear to be, lacking the lens I need to replace.

Of all the solvents, I don't keep any ethanol. I could try it, but really the exterior surface of the meniscus lens well and truly is so roughened as to not be able to see through it. I think there was some layer on top that rendered it transparent and smooth that I have destroyed. I could take some pictures with the old Dynoptic. If I end up purchasing another I will give it a good examination to see what it's supposed to look like.

[apochronaut]

I'm really sorry. one of the links was the wrong one. Try 372649884592 for a head. The two stands I linked to,are sporting longer objectives than the 160mm B&L objectives were. One has very poor pictures but the profile of the objectives is that of the older straight shrould Flat Field acromats. In one picture for the other stand, a 40X Flat Field achromat is evident. It would be unusual for one of the 160mm Dyna stands to have been fitted with the Flat Field objectives but not impossible.

I sometimes will ask for further pictures in order to clarify some important details , and most sellers are pretty good sbout supplying them.....or just what is written on the parts.

Ideally, finding a new doublet would be ideal but I don't think it will be inexpensive. I once had a Balplan that had a chip on the edge of the telan lens. You could just barely see a blur at the periphery with the 100X objective. It's up inside the head and travels as the interpupillary adjustment is made, in order to maintain focus. I did not have much of a choice but to buy one from you know who. $65.00 for one lens + shipping. It makes buying into a cheap derelict stand as a parts unit, a rather attractive option. You never know when you will need something else. You did mention early on that the 10X was o.k. on your scope and that the 40X not. I would be suspicious that the 40X might also have a problem? You might need one of those.

One complicating factor is that the stands were clearly identified during the time when there was production overlap; when the 160mm version and the Flat Field version were both being made. There is evidence though that later, probably after the 160mm Dynas were discontinued, they produced them without the Flat Field designation above the nosepiece. I have seen more than one....many in fact, so the Flat Field heads are probably not necessarily marked as such.

New York Microscope may also have been a fairly voluminous B & L dealer. You might try them. Martin Microscope also became dealers, albeit a bit begrudgingly, after Cambridge and then Leica forced an AO-B&L merger, for a while. Although Martin were solid AO dealers for years, they did later do some B & L service. They are pretty good about finding odd older parts, if they have them. Aaron, is a good guy. I know they do have some B & L stuff.

[BramHuntingNematodes]

Ideally, finding a new doublet would be ideal but I don't think it will be inexpensive. I once had a Balplan that had a chip on the edge of the telan lens. You could just barely see a blur at the periphery with the 100X objective. It's up inside the head and travels as the interpupillary adjustment is made, in order to maintain focus. I did not have much of a choice but to buy one from you know who. $65.00 for one lens + shipping. It makes buying into a cheap derelict stand as a parts unit, a rather attractive option. You never know when you will need something else. You did mention early on that the 10X was o.k. on your scope and that the 40X not. I would be suspicious that the 40X might also have a problem? You might need one of those.

That's absolutely true, and as an economics question it does seem to make sense when the marginal cost over just the part is a few dollars but includes an entire set of objectives, eyepieces, less rusty parts. I have a stereozoom head I got from wstenberg without an arm-- it's a pity they don't fit in the Dyna stand!

Thanks again. I have contacted the above marketers but also quietly resigned myself to purchase that scope you have listed.

[microb]

Could you give dimensions and use a collimated beam of light to find the focal length for red, green, and blue? I'm curious what the corrections might be. But if there is no big frequency difference, then maybe a surplus doublet can be found. Is it planar convex? Or is it a negative doublet?

[apochronaut]

Maybe , read through the thread. The telescope lens system on those is unique and has a specific multiplying factor applied to the objectives; which are incomplete semi-objectives. While I am not 100% sure what the role of that doublet is in the total system, it seems likely that is mostly applies final corrections but it also has to bring the image to focus at the lens above it, which is most likely a 5X magnifier. The objectives in the microscope are 20% of the marked magnification.

[BramHuntingNematodes]

Maybe , read through the thread. The telescope lens system on those is unique and has a specific multiplying factor applied to the objectives; which are incomplete semi-objectives. While I am not 100% sure what the role of that doublet is in the total system, it seems likely that is mostly applies final corrections but it also has to bring the image to focus at the lens above it, which is most likely a 5X magnifier. The objectives in the microscope are 20% of the marked magnification.

In addition, our example lens is badly damaged.

[microb]

So I dug up the B&L that I have, and it has just one lens. But the assembly is different from yours.