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Poitevin discovered that a bichromated gelatin-covered plate could be used to produce prints after being exposed to light through a negative. First, a plate was rendered light-sensitive by coating it with warm potassium or ammonium bichromated gelatin and heating it at a steady temperature in an oven until dry.
After nearly two and a half hours, a negative was placed between the plate and a light source, exposing the gelatin layer to ultraviolet light, and hardening the exposed areas.
In addition to using its own archive of original negatives, the Albertype Company also reproduced photographic images taken by other companies or individuals.
The Albertype Company was created to take advantage of the commercial applications of the collotype, a type of printing which used photographic negatives.
Albert presented his improved collotype process at the 1868 Photographic Exhibition in Hamburg.
Immediately after the introduction of his innovations, companies were able to produce about two thousand prints from each plate using etching presses and hand rollers.
Towards the end of the nineteenth and in the early twentieth century, improvements in mechanical presses and a switch to the rotary collotype, a high-speed process using an aluminum plate, meant that up to five thousand collotype prints could be produced daily.
Sources: Historical Society of Pennsylvania and the Metropolitan Postcard Club of New York City ANC - American News Company This company worked out of 119 Nassau Street, New York, NY between 18 and claimed to be the largest publisher and distributor of books, magazines, newspapers, and postcards in the United States exclusively through their national network of affiliated news agencies.
Collotypes were important to the industry of photographic reproductions because they were fairly cheap to produce, and their range of tones permitted exact reproductions of photographs through a photomechanical process.
They are also noted for their ability to accurately reproduce drawings, prints, and watercolors, and are still in limited use to this day.
An early type was their Sepia Delft series printed in dark high contrast tones.
This was followed years later by their Blue Tone cards that were similar to their lower contrast black & white albertypes except for their color.