Before the invention of the dry plate, photography was a rather messy business. Plates were generally dipped in collodion mere seconds before the actual photograph was taken and then placed in the camera within the confines of a dark-tent to ensure that the collodion was exposed to no light. After the picture, the plates were removed and literally rushed back to the dark-tent for carefully controlled exposure. Even then, pictures often had blemishes and imperfections caused by the running liquids on the plate.
The first "dry plate" was crafted by one Richard Hill Norris in Manchester in 1856. This plate was coated in gelatin, which enabled them to maintain their reflectiveness and exposure powers for up to 6 months. This process was further perfected by adding albumen to the mixture, allowing for an even faster drying process. Finally, Richard Maddox devised the first truly dry plate from silver coatings and collodion in 1871.
These plates took longer to develop than simply selling collodion, and Maddox never took his idea commercially. However, other innovators began devising alternate concoctions, all of which sped up the drying procedure. By 1880, Charles Harper Bennett had created an emulsion process that allowed his silver-collodion-gelatin mixture to become especially light-sensitive - a picture could be developed in just 1/30 of a second.
Over the years, a number of commercial businesses patented formulas for dry plate creation, involving aluminium, bromine, mercury, and tin. All of these businesses thrived, but none of them did so well as the ambitious George Eastman, whose knowledge of machinery and production enabled him to build several machines to speed up the dry plate creation process.
First, he built a machine that would apply the gelatin mixture evenly across a plate. He went into business with a family friend in 1881. (Interestingly a bad batch of gelatin caused the company to temporarily go bankrupt until Eastman, a former banker, secured a loan to keep them in business!) But Eastman's most famous contribution to dry plates was his use of flexible film - able to be rolled up in tight canisters for easy transportation. By 1890, Kodak had become the most popular business in America, and the dry plate was a fixture of photography.
In today's digital age, the use of physical film is becoming rarer and rarer. What an amazing step forward from the days of running around in dark-tents with wet plates and hand-held gunpowder flash bulbs!