Dating foreign postcards
Most old photo papers used silver in their emulsions.As time passes this silver tends to migrate to the surface of the print creating tell-tale metallic patches.At least 450 different real photo postcard backs can be found but as of this time there is a lack of accurate information regarding all their dates of use, or they were used in very limited quantities.Kodak controlled 80% of the paper market with their brands Artura, Azo, Aristo, EKC. Cyko by Ansco, Argo by Defender, and Kruxo by Kilborn comprised most of the remaining market.Sometimes a photographer might expose a logo onto the image or hand stamp a name to the back of the card. Numbering was an essential way of keeping tract of large inventory.
Though most of us today are familiar with the concept of photo grain, this is mostly because we have experienced very large prints made from small 35mm negatives.But even here the effect is more of a softening of detail than a observable texture.Early real photo postcards are small by their very nature and since most were contact printed, not enlarged, there is no visible texture.This could go on for generations, and it is not uncommon to find the same photograph attributed to three different artists.While today this would lead to lawsuits, copyright was uncommon and rarely enforced at the turn of the 20th century.
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The photosensitive solution used in this process soaks into the paper, so the original paper surface remains dominant in the final print.