The introduction of lantern slides in 1849, ten years after the invention of photography, allowed photographs to be viewed in an entirely new format. As a transparent slide projected onto a surface, the photograph could be seen, not only by individuals and small groups, but also by a substantial audience. This new larger scale expanded the utility of photography, changing it from an intimate medium to one that was appropriate to entertainment and educational purposes.
The practice of projecting images from glass plates began centuries before the invention of photography. As early as the seventeenth century the Magic Lantern, or Sciopticon, was used to project painted images on glass for children’s picture shows and for religious displays. (1. Baldwin, p.58) In the 1840s, Philadelphia daguerreotypists, William and Frederick Langenheim, began experimenting with The Magic Lantern as an apparatus for displaying their photographic images. Because the opaque nature of the daguerreotype disallowed its projection, the brothers looked for a medium that would create a transparent image. They employed the discoveries of the French inventor, Niépce de St. Victor, who had discovered a way to adhere a light sensitive solution onto glass for the creation of a negative. By using that negative to print onto another sheet of glass rather than onto paper, the Langenheims were able to create a transparent positive image, suitable for projection. The brothers patented their invention in 1850 and called it a Hyalotype (hyalo is the Greek word for glass). The following year they received a medal at the Crystal Palace Exposition in London. (2. Layne, p.44)
The Langenheims envisioned their slides as forms of entertainment, charging a fee to watch their picture shows. (3. Layne) However, within a few years, lantern slides began to fulfill a variety of purposes. While entertainment remained an important function well into the twentieth century, lantern slides had the greatest impact on educational lectures, especially in visual disciplines. They played a vital role in the development of disciplines such as art and architectural history, making possible the detailed study of objects and sites from around the world. (4. Leighton, p.107-119)
The first lantern slide producers made their slides using albumen-coated plates and, after a short period, switched to wet-collodion plates.(5. Spindler) The introduction of dry plate processes, as well as mass-produced lantern slide kits, made the slides easier for amateur photographers to produce and also made them more accessible to schools and universities. (6. Spindler)
Besides the photographic medium itself, the process for creating lantern slides remained primarily the same throughout their one hundred year history. There were two ways of printing the images: the contact method and the camera method. The first dictated placing the negative directly on the light-sensitive glass. This required that the negative was the correct size to produce the 3.5x4 inch slide. For larger negatives, the camera method was necessary. Using a camera with a long bed and bellows, the negative and glass were both placed in the camera and printed by exposing the glass to daylight or artificial light. After exposure in both cases, the latent image was developed out with chemicals. After the plate was dried, the image could be hand-colored using special tints. The slide was finished with a mat and a glass cover and was taped to seal the enclosure.(7. Elmendorf)
The finished product was placed within a lantern slide projector to be viewed on a wall or screen. The first projectors used oil lamps for light. By 1870, limelight, produced by burning oxygen and hydrogen on a pellet of lime, offered a better, although more dangerous, form of illumination. In the 1890s, the invention of the carbon arc lamp, followed by electric light, provided a safe method for displaying the lantern slide image. (8. Spindler)
Use of lantern slides lasted throughout the remainder of the nineteenth century and until the 1950s when their popularity began to decline with the introduction of the smaller 2x2 transparencies.(9. Spindler) Finally, the discovery of the Kodachrome three-color process made 35mm slides less expensive to produce than lantern slides.(10. Freeman, p.336) Although their production ended over 40 years ago, many academic slide collections still house and use glass slides. In some cases, the views that they represent are either drastically changed or no longer exist and thus they are invaluable images of the world during the nineteenth and early twentieth centuries.
For further information, see Bibliography for Lantern Slide History