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How did the old glass slides work? I think I have found a couple "thingys" that were used for glass slides back in the day, but I have no idea how they were projected.

I also have a pair of those old glass slide projectors from the 1920's, and have never fired 'em up, but the ones I have are AC carbon arc lamphouses with a power supply (just a resistive network in a ventilated steel box) to drop the incoming AC to the voltage the carbons were designed for... The uncoated carbons are huge (about 3/4") in comparison to the Suprex copper coated carbons used in most of the later carbon arc lamphouses for motion pictures... The lamphouses I have used no reflectors, just the light collected directly from the arc... The slide projector has a very simple back and forth slide holder which allows you to show one slide while manually loading the next slide you would be showing... The lens is also a very simple one element affair...

I also have about 200 of the hand painted glass advertizing slides which were used with these, and some are beautiful... Several years ago I made an adapter to fit these and used a huge enlarger at a local high school AV department to project them onto a large sheet of white paper... I videotaped about 25 of them to be included in a historical video I made for the local historical society...

Those projectors were still used in the local theaters well into the 1940's and I remember seeing those slides shown as a small child... Much like what many are using as pre-show advertizing today...

There is likely quite a bit of interest in lantern slides on the antique collectors market, especially if the subject of the ad is familiar and the condition is good. Some film archives may also have an interest and accept donations of slides:
http://www.geh.org/lantern.html
http://www.geh.org/ar/strip64/htmlsrc2/comingat_sum00001.html
http://amianet.org

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John P. Pytlak, Senior Technical Specialist
Customer Technical Services
Entertainment Imaging
Research Labs, Building 69, Room 7525A
Eastman Kodak Company
Rochester, NY 14650-1922
Telephone: +1 585-477-5325 Cell: +1 585-781-4036 Fax: +1 585-722-7243
E-Mail: This e-mail address is being protected from spambots. You need JavaScript enabled to view it
Website: http://www.kodak.com/go/motion

This probably won't surprise anyone here, but I'm still using my 4"x4" glass slide projector on a daily basis.

There are many different kinds of those projectors. The largest of them were called Brenographs, "a super magic lantern that not only projected song slides for the organ interlude, but an endless variety of scenic effects by means of multiple lenses and intricate fades and dissolves" as quoted by Ben Hall in the book The Best Remaining Seats. I have one of those, a slightly smaller model (but believe me, not small) that was called the Brenograph Junior. I don't use that as it is carbon arc. Too much of a bother. I use a much smaller slide projector called a Opticon. It uses a 1000 watt bulb. I have a few old ad slides, and many sing along song slides, but what I use it for on a daily basis is to project a message across the bottom of the screen that says "Concession Stand Closes in 5 minutes" which naturally is projected a little over five minutes before the stand closes for the evening. That slide that cost me $3.50 back in 1970 has brought in about $100,000 in otherwise lost concession sales over the past 35 years.

Well worth using.

"I use it for on a daily basis is to project a message across the bottom of the screen that says "Concession Stand Closes in 5 minutes" which naturally is projected a little over five minutes before the stand closes for the evening."

Although it certainly helps your bottom line, I hope you agree that projecting this across the bottom of the screen during the movie is not the best example of showmanship.

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John P. Pytlak, Senior Technical Specialist
Customer Technical Services
Entertainment Imaging
Research Labs, Building 69, Room 7525A
Eastman Kodak Company
Rochester, NY 14650-1922
Telephone: +1 585-477-5325 Cell: +1 585-781-4036 Fax: +1 585-722-7243
E-Mail: This e-mail address is being protected from spambots. You need JavaScript enabled to view it
Website: http://www.kodak.com/go/motion

Well John, this is one time where I think that you are 99% WRONG!

Usually the 5 minute notice comes on during the trailer of the final showing for the day. There are times when it comes on during the opening credits of the feature, before the story line begins, but I try to avoid that as much as possible. Once in a great while it will be used in the middle of a feature, but only during kiddie shows when the stand is kept open longer.

I would think that you of all people would remember that it was standard policy in many major theatres years ago to use those slide projectors to project daters across the bottom of trailers informing people as to when that film would be coming. Things such as Starts Friday, Special Holiday Show, Extra Late Show Saturday etc, etc. Sometimes they were used to page people during the feature, rather then make an announcement that would be disruptive. Don't you remember those little red paper slide inserts that you could buy from theatre supply houses that you put in your typewriter, and could then type a message on them, put them between the glass slides and project them on the screen?

That little line of copy comprising of five words sitting on the very bottom of the screen, just an inch or two above the bottom masking, appearing for 5 seconds, doesn't interfere with anyones enjoyment of the film. As a matter of fact, not one person, may I repeat, NOT ONE PERSON has ever complained about it over the past 35 years. Many people have actually told me they appreciate that they are informed as to the closing of the stand, otherwise they would have come out later to find it closed and been disapointed.

That IS SHOWMANSHIP. A way to present all facets of your programing in a professional pleasing and unabtrusive manner. It has actually become an expected part of the program to my patrons. They are the ones that ultimately determine what policies are continued, and this is one they want.

At a time when theatre owners think that presenting preshows filled with nothing but too many trailers, and obnoxious paid advertising, all strung together with no cohesive plan without daters, have no curtains, and don't utilize lighting as part of their presentation... you think that a little slide projected on the bottom of the screen will offend someone?

I'll let the patrons continue to make that call. I have the highest grossing subrun theatre in Pennsylvania. It obviously isn't chasing away many, if any, patrons. I think that if they have compared the showmanship at this theatre to any other theatre in Pennsylvania, that one little offense, if indeed it is one, doesn't even begin to compare.

I have no issue with projecting something under the image during trailers, or even the closing credits. But I personally would not like it if it occured during the story that I paid to see.

When I worked at a drive-in, I convinced my manger that making snack bar announcements DURING the film was not good showmanship. People commented favorably on discontinuing the practice.

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John P. Pytlak, Senior Technical Specialist
Customer Technical Services
Entertainment Imaging
Research Labs, Building 69, Room 7525A
Eastman Kodak Company
Rochester, NY 14650-1922
Telephone: +1 585-477-5325 Cell: +1 585-781-4036 Fax: +1 585-722-7243
E-Mail: This e-mail address is being protected from spambots. You need JavaScript enabled to view it
Website: http://www.kodak.com/go/motion

There used to be a cellophane film that was sandwiched between two pieces of carbon paper that one typed on called Radio Matte and then put between two pieces of glass

Gordon, I discovered some of those sheets also.