A note on downloading the PDFs: most of these files reside in a Dropbox cloud, so depending on your platform and browser and PDF reader plugins you might have, it might take a couple clicks on “download original” or some such. Also, some of these are very large files so downloader beware!
“On the Use of Collodion in Photography” (Frederick Scott Archer, in The Chemist, 18 February 1851)
The Collodion Process on Glass (Frederick Scott Archer, 1854)
Ambrotype and Photographic Instructor (M.H. Ellis, 1856; 1.82mb)
A Treatise on the Positive Collodion Process (Thomas Sutton, 1857; 23.2MB) *Recommended for state-of-the-art 1850s*
The Silver Sunbeam (J. Towler M.D., 1864)
A Manual of Photography (Mathew Carey Lea, 1868)
Handbook of the Practice and Art of Photography (Hermann Vogel, 1871; 124.6 MB)
Trask’s Practical Ferrotyper (1872)
The Chemistry of Light and Photography (Hermann Vogel, 1882; 18.6 MB)
The New Recreation: Amateur Photography: A Practical Instructor (D.J. Tapley, 1884) *On dry plate, but a delightful glimpse into the social history and practice of late 19th-century photography; a fun easy read — with pictures!*
The Photographic Negative (W.H. Burbank, 1888; 95.8MB)
The Photographic Image: A Theoretical and Practical Treatise of the Development in the Gelatine, Collodion, Ferrotype, and Silver Bromide Paper Processes (P.C. Duchochois, 1891; 10.5MB)
The Ferrotype and How to Make It (Edward M. Estabrooke, 1903; 9.8MB)
Collodion and the Making of Wet-Plate Negatives (Kodak, 1935; 12.3MB)
Original Patents for Headrests (ZIP archive, courtesy of Borut Peterlin)