Hi all,
Most of my old Zeiss Plan(apo)chromat (dry) have relatively large front lenses. They have a polished, concave center and the surroundung area is frosted, rough glass.
I have now looked at some Nikon objectives. The plan lenses have the same concave center area but the surrounding glass is covered by a thick layer for black varnish/sealant. Presumably this is to block out stray light.
I now have a used Nikon Fluor 40/0.85 Corr objective in which the black varnish has been completely stripped. Normally, it should be there as seen on this image: http://i1217.photobucket.com/albums/dd3 ... ea78ca.jpg
Can anybody say how important the black varnish is for the function of the objective? I don't have an unstripped one to compare it to.
Anyone know what it is made from? The front lens seems an odd place to use a varnish or any kind, since the users will use aggressive solvents like xylene to clean them - few materials are not dissolved by it.
On the other hand, even my Leitz 50/1.0 Oil objective has that black varnish around the front lens - if it is that robust, how could anybody strip it completely from the Fluor 40/0.85?
Kind regards, Ichthy
Nikon objective front lens: Black varnish
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Ichthyophthirius
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The black varnish on the Leitz could be black high temp ie ceramic or vitreous enamel.
You could replace the black varnish with a two component black epoxy (which you might have to formulate yourself but it would not be very difficult)
Epoxies are pretty xylene resistant unless soaked (they tend to swell). But solvent could penetrate the bonding layer and pop the whole coating off in one piece.
There are all kinds of "stained glass" coatings at my local art supplies store. Some of these want to be baked in the oven, but not at vitreous enamel fusing temps (which are cherry red hot) but rather about 250 degrees F or so. These probably utilize the ovens heat to drive off all the carrier solvents and also to promote polymerization and bonding to the substrate.
Unfortunately higher temps than you might want to expose lens cement to.
You could replace the black varnish with a two component black epoxy (which you might have to formulate yourself but it would not be very difficult)
Epoxies are pretty xylene resistant unless soaked (they tend to swell). But solvent could penetrate the bonding layer and pop the whole coating off in one piece.
There are all kinds of "stained glass" coatings at my local art supplies store. Some of these want to be baked in the oven, but not at vitreous enamel fusing temps (which are cherry red hot) but rather about 250 degrees F or so. These probably utilize the ovens heat to drive off all the carrier solvents and also to promote polymerization and bonding to the substrate.
Unfortunately higher temps than you might want to expose lens cement to.