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Author Topic: Repair Cement For Lens Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 11-20-2009 07:52 PM                     The best cement is of course no cement or just use todays modern cinema lenses. Balsam is fine for optics that are not exposed to alot of heat. You've all seen lenses that have been baked by large arc or xenon liht sources. The cement typically used today is a UV curable optical cement. It has much better properties than balsam and lenses re-cemented with the stuff actually improve. The cement also does not yellow over time. Summers UV Curable Optical Cement Mark  |  IP: Logged Tony Gallimore Expert Film Handler Posts: 108 From: Willis, Virginia, USA Registered: Jul 2009 posted 11-20-2009 08:48 PM                     Thanks!! I appreciate every ones input. As I mentioned initially, the cement source I found here in the lower 48 wanted to stick a huge shipping charge (much more than the cement itself) on it because it's considered hazardous material, at least that particular government version of balsam cement was. I'm not desperate to keep the lens, except in using the variable in my home theatre application, I really would never need to change the lens... just reset it for a flat print and change the aperture plate. Image size wouldn't be a major problem with my setup. Yes, it does sound pretty lame avoiding a thirty second lens change. I guess I became attached to it (the variable) back (in the carbon days) when I was working the cinema in the 70's and 80's before National Screen Service provided trailers in scope. We used the variable very successfully running flat trailers plus back then a cartoon as well as local commercials on film, up against a scope feature. We did a lot of curtain play with it making for a pretty nice presentation. Anyway, THANKS guys, I'll think on it a little more and then probably go for the new anamorphic.  |  IP: Logged Tim Reed Better Projection Pays Posts: 5246 From: Northampton, PA Registered: Sep 1999 posted 11-20-2009 10:52 PM                       quote: Summers Optical, Hatfield, PA 19440 Practically in my backyard.  |  IP: Logged Randy Stankey Film God Posts: 6539 From: Erie, Pennsylvania Registered: Jun 99 posted 11-20-2009 11:04 PM                     The balsam in on the site I found is just a chunk of purified tree sap. I can hardly think of a reason why it would be hazardous. However, you are supposed to break up the chunk of resin, mix it in xylene and heat it until it dissolves. That could be tricky. Seeing this subject come up inspired me to read up on the subject. There are several sites where people talk about repairing telescope lenses, rifle scopes and camera lenses. I see little reason why a projection lens would be much different. From what I've read there are two main hurdles to getting the repair right. First, is the proper preparation and application of the cement. Second is getting the glass aligned correctly. The xylene used to dissolve the balsam is flammable. If you have to heat the mixture to make the cement, that could pose a hazard. I have also read that you should mark the lenses before you take them apart. Old lens elements are oriented rotationally as well as laterally. Before computerized grinders were invented, there were imperfections which were compensated by rotating the two elements until they aligned. More than one person said that you should mark the lenses before taking them apart so you can get them back into the correct orientation. I also read that a lot of people still like to use balsam instead of UV curable cement because balsam is easier to remove than the synthetic. If you ever have to rework the lenses, it will be difficult to separate them again after using UV cement. With balsam, you can just drop them in hot water and they should come apart fairly easily. I'm not saying I'm an expert, here. I'm just telling about what I read. Like I said, you have nothing to lose by trying.  |  IP: Logged Frank Angel Film God Posts: 5305 From: Brooklyn NY USA Registered: Dec 1999 posted 11-20-2009 11:54 PM                        Can anyone explain why older lenses had to be cemented while modern lenses don't? Is it because they can get higher tolerances in the mounting body today so they are held together more perfectly? Just guessing. Seems like a big jump from needing to be cemented together to just being held that way mechanically.  |  IP: Logged Bernard Tonks Jedi Master Film Handler Posts: 619 From: Cranleigh, Surrey, England Registered: Apr 2001 posted 11-21-2009 03:10 AM                     quote: Pete Naples I was once told by a man who worked on Submarine periscope optics that (IIRC) perspex dissolved in Acetone was what they used. I don't know about the US or Canada, but here you'd have the devils own job trying to obtain Acetone these days. Nail varnish remover seems to be Acetone by the strong smell of it.  |  IP: Logged John Hawkinson Film God Posts: 2273 From: Cambridge, MA, USA Registered: Feb 2002 posted 11-21-2009 06:40 AM                     Acetone is the active ingredient in nail polish remover sold here in the US. Probably true in the UK too, though I'm quite surprised to find you can't purchase straight-up acetone at the local hardware store. Frank, if we take Mark's explanation, it is that modern lenses are cemented with UV-curing cement, which can withstand substantially higher temperatures and doesn't crumble and degrade like the old stuff did. So straightforward advances in adhesive technology. --jhawk  |  IP: Logged Stephen Furley Film God Posts: 3059 From: Coulsdon, Croydon, England Registered: May 2002 posted 11-21-2009 06:40 AM                     It used to be, or at least it used to contain a lot of acetone, but I think they use other solvents now.  |  IP: Logged Louis Bornwasser Film God Posts: 4441 From: prospect ky usa Registered: Mar 2005 posted 11-21-2009 07:29 AM                        Acetone can be purchased by the gallon at any Lowes or Home Depot. Louis  |  IP: Logged

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