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Thread: How I did it: new balsam for a sick RR

  1. #11

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    Re: How I did it: new balsam for a sick RR

    CLEANING AFTER SEPARATION

    The two component lenses (flint and crown) will look very messy after this separation. The small amount of balsam used is enough to create a very lumpy appearance. The cleaning may have two stage as there can be edge deposits which are not soluble. Using protective gloves, take the lens up and clean with xylene impregnated paper towels. The deposit does not come away from the surface easily and mechanical rubbing is necessary to get it on the paper. Throw away the papers quite quickly as you soon reach the stage where you put more back on than you remove with each stroke. The quality of the cleaning papers should increase as you get near the surface.

    You may discover a whitish deposit at the very edge. I have no idea what this is (perhaps sugar?) but must be a result of the decomposition of the complex mixture which balsam is. To be honest, I loosened this with my finger nail edge.
    I enclose photos which show the general appearance of the crown/flint set, both before and after cleaning. The white edge is also shown.

    Hope someone is finding this account useful or amusing!

  2. #12

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    Re: How I did it: new balsam for a sick RR

    Quote Originally Posted by Steven Tribe View Post

    Hope someone is finding this account useful or amusing!
    i am ! i have a soft spot for Suter lenses. i have several. i love them. i would like to see yours. i have the series B #6 and #8 (early serial numbers) and a petzval that are my favorites.

    if you need more practice i have some lenses to send you....LOL

    eddie

    Edit: to add the picture of my baby....
    Last edited by eddie; 7-Feb-2010 at 07:11. Reason: add picture
    My YouTube Channel has many interesting videos on Soft Focus Lenses and Wood Cameras. Check it out.

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  3. #13

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    Re: How I did it: new balsam for a sick RR

    I understand it is a good idea to mark the edge of the lens being separated with two light marks at 90 deg to each other on the edge, with a fine sharpening stone, to make it possible to re-register the lens in it's orig. alignment during re-cementing. Is this necessary?

  4. #14
    ARS KC2UU
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    Re: How I did it: new balsam for a sick RR

    Quote Originally Posted by Steven Tribe View Post

    Zylene/Zylol is a standard product available locally.
    Steven: Don't forget that the Zylene you are describing (yes it is a good solvent) is spelled with an "X" in the US: i.e., Xylene.

    If one goes looking for Zylene here there will be confusion. Bob G.
    All natural images are analog. But the retina converts them to digital on their way to the brain.

  5. #15
    ARS KC2UU
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    Re: How I did it: new balsam for a sick RR

    Quote Originally Posted by Steven Tribe View Post
    But they can be split quite easily with methylene chloride (carefull - a wicked solvent).
    The good news with methylene chloride is that it is so irritating that one is not likely to work with it for long voluntarily and be badly exposed.

    The bad news is that carboxyhemoglobin and formaldehyde are produced in the body as it metabolizes and formaldehyde is a carcinogen. i.e., as a result methylene chloride (a.k.a., dichloromethane) is also considered to be carcinogenic.

    Further bad news is its vapor pressure is so high that it tends to go right through standard respirator cartridges very quickly.

    My advice; If you decide to use it make sure there is excellent ventilation to keep the vapors out of your breathing zone.

    Regards. Bob G.
    All natural images are analog. But the retina converts them to digital on their way to the brain.

  6. #16

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    Re: How I did it: new balsam for a sick RR

    Thanks for the feedback!

    Xylol/Xylene is spelt that way here, too! Sorry about the careless slip!

    "I understand it is a good idea to mark the edge of the lens being separated with two light marks at 90 deg to each other on the edge, with a fine sharpening stone, to make it possible to re-register the lens in it's orig. alignment during re-cementing. Is this necessary?" No, the lens are spherically gound/polished so there should be no problem with allignment at 13, 79 or 271 etc. degrees to the original glue position which was quite random. More useful would be micrometer measures of the distance from the edges of the flint to the crown and the distance the flint sticks up above the surface of the crown. I tried but found the job beyond my skills with a micrometer. There is good reason to believe that a pair suffering from separation no longer has the original orientation.
    I have decided to enclose a later section about optically checking the success of the
    positioning of the lenses.

  7. #17

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    Re: How I did it: new balsam for a sick RR

    I am not sure how easily methylene chloride (CH2Cl2) is available anymore. It used to be the active component in really effective paint removers. Perhaps "wicked" was an understatement. The commericial product was rather gel like so there was time enough to place a dollop in a glass container (not plastic here) close the lid and retreat quickly inside.

  8. #18
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    Re: How I did it: new balsam for a sick RR

    Well paint stripper is still available in the UK, that's mainly methylene chloride.

    Ian

  9. #19

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    Re: How I did it: new balsam for a sick RR

    PROPERTIES OF CANADA BALSAM AND HOW TO GET IT ONTO THE CONCAVE SURFACE.

    This section is based on a period of about eight, mostly very unsuccesful, attempts. I followed the recommended procedures as well as trying out thinning the balsam. This series of experiments was mostly to get a methods which avoided air bubbles. In summary, Both lenses need to be warm, the balsam cool and the balsam needs to be "melted" into the centre.

    Proper balsam is stiff and will only just "pour" or "fall" out of its container. It has a very strong aroma which is about as dangerous as walking past a row of freshly felled trees! In the container, there are no signs of air bubbles. However, once formed, they stay there for a long time.

    Attempts to use a small quantity of xylene thinner (less than 5%) produced a more rapidly flowing substance - with few air bubbles - which allowed a succesful bond with cold lenses. Unfortunately, a permanent haze appeared throughout the cement layer.
    Conclusion: use Canada Balsam and warm lenses.

    I began to realise that the first application of the balsam is crucial. The wrongly applied balsam, even on warm concave surfaces, produces quite a few air bubbles. Photo 1 shows the typical results of wrong application. The amount deposited is much more than necessary!

    The way to apply the balsam is to facilitate a direct physical contact between the hot lens and the balsam so that the balsam warms instantly and seeps down onto the lens. I have tried this with both the container itself and a thickish (5mm - 10mm) glass rod. It takes just a few seconds for this to allow enough balsam to spread out in the centre. Working with a pipette or allowing drops to fall from the container doesn't seem to work at all (Photo 2).

  10. #20

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    Re: How I did it: new balsam for a sick RR

    My only experience with Canada Balsam is for making geological sections. You need to cook it enough so it hardens, but not so much that it discolours. According to my lab reference for geological section making, around 3 minutes at 85C would do it. This is for low mas items like 3x1 microscope slides and small blocks of rock. The usual test was to pick up a small bead on a mounting needle and see if it hardened when it cooled.

    Air bubbles can be led to the edge with a needle while the cement is fluid. The trick is to let the balsam flow. Trying to stir it or push it tends to add bubbles. Making sections we could push bubbles ahead of the specimen by lowering on one edge first and then forcing out the cement. Again, not something that will work with curved lens surfaces, though capillary action should help.

    We used a lot of thermoplastic mounting medium (Lakeside 70C) because it was a) cheaper, and b) did not need to be cured so precisely (both good qualities when training students). We usually cleaned mounted and covered slides in methylated spirits with an old toothbrush and a single edge razor blade. Not the sort of thing to do casually with old optical glass!

    Xylene is nasty stuff. It will help remove epoxy resin, though.

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