Glad I found this. I've a 600mm APO Voigtlaender Skopar that need this done to it. Never had any luck with the later cements. Wrecked a 240mm f5.6 Rodenstock messing around with it. Hot water? go figure.
Glad I found this. I've a 600mm APO Voigtlaender Skopar that need this done to it. Never had any luck with the later cements. Wrecked a 240mm f5.6 Rodenstock messing around with it. Hot water? go figure.
Joseph - I redid a big Suter aplanat (A no. 4). I spent hours gouging out a channel to remove what I thought was a lathe turned down edge. Finally, I realised that there was an L shaped washer where the protruding edge had been pushed down inside the barrel casing edge!!
Completely impossible to see - even with the black enamel removed. It might be worthwhile checking yours for the same assembly method.
I don't think this warm "manipulation" will work with balsam. The balsam will be discoloured by now and the separated solids will prevent movement.
Thanks Steven-
It sounds like I'd be better off leaving it as it is-
just stopping down by one removes the offending edge-
It would be good to re-cement, not least to improve the value, but a description that includes 'some separation' might be preferable to one that reads 'gouged'...
Re-reading, removing the black paint would seem to be an important step-
impossible to verify with the group contained within the brass assembly...
How would I mount a smaller lens on top of the bigger ones...I'd have to center them very well?
This will have to be moved over to the "new" DIY section.
Mounting a smaller lens on top of a larger lens is not difficult. This is quite a common construction, for instance, Protar series VII. The spherical surface will fit precisely in the "hole". Just press home around the edges until the edge of the smaller lens has the same distance from surface of the larger lens.
I've done a number of lenses with the boiling water trick, until I discovered furniture stripper is less stressful (both for the glass and for me). I just put the lens assembly into a glass jar with a tight lid, enough MEK-based stripper to cover plus a bit, and let it do it's magic. On a large modern UV-glued lens, it might take as long as a week, but eventually I swirl the jar a bit and find the lenses are floating separately. A judicious poke with the tip of a pencil might speed up the separation a bit, and the advantage of the stripper is that the lenses only need a minimum of wiping to clear the gunk off, and a rinse in alcohol before re-gluing.
I was going to start a new discussion but since this one's been revived -- thanks, Albert -- here goes.
Years ago I was given a 58/5.6 Grandagon ex-Graflex XL. The glass was clean in the sense that there were no scratches or fungus but both cells had major separation. Both had rings of fire around the periphery, the rear cell had silver spots near the center. Many Rodenstock lenses from that era have similar separations.
I tried it out anyway. It shot quite well and is one of the shortest lenses that will focus to infinity on a 2x3 Pacemaker Speed Graphic. Unfortunately putting it on the camera is a pain because the rear cell is too large to pass through the front standard. The procedure is: unscrew rear cell, attach board with shutter and front cell to the front standard, put the rear cell back in the shutter from behind the camera. Reverse to take the lens off the camera.
After I got 65/8 Ilex that went on the camera without all that fiddling I put the Grandagon in the drawer. I recently took it out. It seems to have healed itself. The rings of fire are nearly gone and the silver spots in the rear cell are nearly invisible.
This is not supposed to happen. Separation is permanent. Do any of you have badly separated lenses that seem to have healed?
Short answer is no. But I have only experience with Balsam, where entry of air means that the balsam degrades into a whitish coating on the two lens surfaces. When the balsam is still in good condition, when warmed it will become more fluid and expand a little and could "repair" edge damage.
But please don't try with hot/boiling water. The heat transfer into the glass is very rapid with water and you create internal stress. Use an oven.
Separation with synthetics is a very different barrel of fish. It is more loss of adhesion with air gaps in the realm of light's wavelengths - hence Newton's rings. I can easily imagine this might heal itself. The flecks you mention sound like macro-crystal growth, which I have also seen in balsam. Crystals can also change in appearance.
I used acetone, fingernail polish remover. Removed lens cell from lens and soaked it for about a week. I could see the balsam dissolving as I checked it daily. Eventually slid apart easily.
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