Preserving/Documenting Lantern Slides: How do I not ruin them?

April 28, 2011 8:27 AM

My family has a collection of 35 lantern slides dating from the 1880-90's. They are black & white photographic images, with some handcolored. They are in reasonably good condition and I would like to somehow transfer them into a digital format. Is it OK to lay these on a scanner, or will strong light exposure risk damaging the slide images? Is there a better way to photograph or reproduce the images?

Also, the slides are fairly clean, but some have a faint patina of what looks like mold on the surface of the glass. Is it safe to clean them? I haven't taken any of the slides apart, but they seem to be constructed by fitting two pieces of glass together. I assume the image is fixed on the internal side and therefore it would be OK to wipe the outside with a damp cloth. Note, I have found some references on the internets indicating that this is OK, but I've also observed that lantern slides were an evolving technology from 1850 to 1950, and so the same recommendations might not apply to all slides.

The slide images were taken/assembled in India by my great grandparents, who were German missionaries there. Apparently my great grandfather used the slides to accompany lectures he did later in Germany and US about Indian culture and religion. I have an accompanying list of notes that he used for his presentation. Example, example.

Bonus: If I can somehow manage to transfer the images into a digital format, I would not mind donating the slides to a museum or research institution. Any ideas on who might be interested in such an acquisition?

posted by amusebuche to media & arts (12 answers total)

Williams College has one of the few art departments that still uses lantern slides. I am not sure about preservation/restoration but someone in the VRC department definitely would.

Disclaimer: I am a Williams College Art History major.
posted by DeltaZ113 at 8:33 AM on April 28, 2011

No matter what anyone says about cleaning the slides, to be safe I would first make sure you got good, clean scans of the entire collection before trying to clean any of them, just in case. As you said, this was an evolving technology, and there are always exceptions to every rule. Who is to say some of the slides weren't disassembled and incorrectly reassembled at some point? You can work a lot of clean-up mojo in Photoshop, once you have them scanned.

I don't see why scanning them with a good flatbed scanner would be any worse than exposing them to daylight, as long as nothing stuck to the glass. While most scanner lamps are fluorescent bulbs and do emit a certain amount of UV, I would think the relatively low power of the bulb and the brief exposure time would be no more detrimental to the slides than handling them in a bright, sunny room.

The trick is that you'll likely need a "slide scanner" or something with a backlit cover. Even with most brand-new copiers and dedicated scanners, normal 35mm slides don't scan properly without a backlight. Unfortunately, most consumer-grade scanners that do have backlit slide and negative adapters will only fit standard 2x2 35mm slides, or 35mm or smaller negatives. There are specialized film scanners that would probably accommodate your slides, but that could get pricey.

It's not too hard to make your own backlight for your scanner; a sheet of plexiglass, frosted, and some white LEDs and you'd be in business. It wouldn't be perfect, and certainly not color-calibrated, but your source images would leave a lot of room to wiggle.
posted by xedrik at 8:55 AM on April 28, 2011

Good point, xedrik. I had not considered taking a set of scans prior to cleaning, but this is excellent advice. Will have to either find a slide scanner with the right dimensions or figure out how to create a backlight.

And DeltaZ113, I am aware that a lot of universities have lantern slides in their historical archives, but wasn't aware that anyone still used them. I will see if I can contact someone at Williams.
posted by amusebuche at 9:54 AM on April 28, 2011

I've scanned hundreds of lantern slides using first an Apple One scanner and later a LaCie scanner with a transparency adapter. If you didn't want to invest in the technology yourself, I believe you could have the slides scanned commercially. Even the Kinkos here in my town will do this.

The church that sent your grandfather on his mission to India might want the slides and his presentation notes. Where did he go to school? That institution might appreciate them as well. The slide collection I scanned resides in the archives of Pittsburg State University in Pittsburg, Kansas. You might contact your college's library and ask them to help you find a permanent home for your collection.
posted by S'Tella Fabula at 9:59 AM on April 28, 2011

Since the slides are about 125 years old, I think I would trust myself more than someplace like Kinkos to do any scanning. So I will look into getting set up at home.

I am currently researching possible places for donating the collection. The church is one possibility, although we don't have detailed enough records to pinpoint exactly what church or organization this might be, though there seems to be an implied affiliation with the Leipziger Mission. We have no records of his schooling. For some reason, we ended up with the slides, but very little other documentation about the family's time in India. It seems it was common to send newly-ordained Lutheran ministers to foreign missions.

In any case, I can't help feeling like donation to a church might result in the slides being boxed up in a cellar somewhere and forgotten (which is no better than they are now). I feel like they might be of more use and relevance to an educational or historical institution. But who knows? I'll continue to look into this.
posted by amusebuche at 11:52 AM on April 28, 2011

Perhaps the George Eastman House might have some answers on this. Main page.
posted by Rashomon at 12:52 PM on April 28, 2011

Yes, contacting anyone at either the WCMA or the VRC is your best bet. Please MeMail me if you have any questions or need any contact info, the departments are very small and exceptional at this type of work.
posted by DeltaZ113 at 1:13 PM on April 28, 2011

As this page notes,

Like photographs, lantern slides are layered structures. They are composed of a glass support layer, with an image-forming material (usually silver particles) embedded in an emulsion layer that has been adhered to one side of the glass. In some cases, a second sheet of glass is laid over the emulsion layer and attached to the lantern slide by wrapping the edges with binding tape.

Hopefully your slides have the cover glass to protect the image. If so, you can probably clean the two outer glass surfaces safely, if you're careful to avoid letting any liquid get between the two sheets of glass.

However, if your slides are just single sheets of glass, then one side of the glass has the image stuck to it with emulsion. This is a very fragile layer and can easily be irreparably damaged by moisture, scratches, or abrasion.

So, yeah, probably a good idea to consult with some lantern-slide pros before you do anything.
posted by exphysicist345 at 3:51 PM on April 28, 2011

Yes, exphysicist345, while the slides vary slightly in their size and construction (some are just taped, others are mounted in cardboard frames), they all seem to be double-plated and are of the same thickness. But I am quite concerned about disturbing any of the images, so will make sure I get some expert advice before I attempt to clean them.

Thanks everyone for all the answers so far. I hesitate to mark "best answer", since all have been informative. You've helped me identify some good resources, and reassured me that I'm on the right track. If anyone else has any expertise or information to add, please feel free to offer further thoughts.
posted by amusebuche at 6:19 PM on April 28, 2011

What a wonderful heirloom. Could you try some compressed air, I wonder how much of the debris would come off that way?
posted by Nickel Pickle at 6:50 PM on April 28, 2011

Update: Over the past week I've had some luck contacting staff at Williams College and the U. of Chicago Film Studies Center. In case anyone else comes to this thread for information about lantern slides, I thought I would share the information I'd collected:

*** There are standard sizes that can help to identify the source country of the slides: In 1889 the International Congress of Photography in Paris established standard dimensions in lantern slides for Continental Europe (3.35x3.95 in.), Great Britain (3 1⁄4 x 3 1⁄4 in) and the US (3 1⁄4 x 4 in.)

*** Lantern slides are projected upside down and backwards in a slide carrier that fits between lenses. There may be markings to indicate the front of a slide as a projection guide.

*** It is safe to clean the outside surfaces of the glass. Unfortunately, mold on the emulsion is a common problem.

Suggested cleaning method for lantern slides:
1. Wipe glass with photo-clear towel to remove loose dust.
2. Next, wipe with non-abrasive wipes (Ped Pac, lint free ultra soft).
3. Apply a small amount of 91% Isopropyl alcohol to the wipe.
4. With even stroke wipe the remaining dirt from glass
5. Gently wipe the glass again with the non-abrasive wipe to dry

During this process, it often becomes apparent that the tape used to seal the glass plate sandwich is rather fragile due to the ageing adhesive in the tape. Labels (a critical source of information about the slide) are also fragile due to ageing adhesive component. If necessary, resecure original tape with silver tape (Delta 1 Silver Mylar 1/4").

For interior mold, you can correct it in photoshop if it is minor without too much difficulty.

*** Scanning is perfectly safe and recommended method of documenting the slides. Light from scanning will not damage the image; it is too short a duration to have that effect.

*** For scanning, make sure to remove the cover on the inside of the lid of the scanner, as that will allow light to pass through the slide from above and below. Leaving it in place will give you a blurry image. In the settings, set it film/positive film; 8 bit for B&W. We use a standard resolution of 300, with the pixel size of the image set as close to 3000 x 2000 as possible. Other sources may suggest a higher resolution, but it is the pixel dimension that is important to us. We go higher for exceptionally high quality slides. We don't turn on the "dust removal" setting, as it will remove some of the fine lines in the image, reducing the quality of the image. We don't find the need to change the focal position of the sensor, as is suggested in some sources, as the above directions work well for us - try first following the above directions and see if that doesn't improve the scanned image; if not, it has been suggested to reset the focal position to 1.0 instead of the default of 2.5.

*** The Image Permanence Institute of the Rochester Institute of Technology and
Chicago Albumen Works in Housatonic, Mass. were suggested as two potential sources for more information on lantern slide management.

*** The Library of Congress’s American Memory website has a history of lantern slides.
posted by amusebuche at 9:09 AM on May 5, 2011

Thanks again for your help, everyone. This project is becoming very interesting.
posted by amusebuche at 9:10 AM on May 5, 2011