For most people, photographs are digital files that pop up on a screen, pictures you can copy, send, post and view with the touch of a finger.
But what if a photograph were an image bonded to a metal surface in a demanding process that resembles a chemistry experiment? Something that feels heavy in your hand, that you can hang on the wall, that your ancestors might be looking at 150 years from now?
That kind of photograph would be a tintype, one of the earliest forms of photography. While the technology had its heyday during the Civil War, it's now being resurrected by some young photographers looking to create something with more gravity than another cellphone selfie.
It's the specialty of Carla Alexandra Rodriguez, a 30-year-old artist who has been using the tintype technique to create evocative studio portraits and fine art images.
Rodriguez, who grew up in Houston, came to Minnesota to study photography at the Minneapolis College of Art and Design (MCAD). From the beginning, she was attracted to older, analog forms of photography that required chemicals and darkrooms.
"The harder it was to do, the more I liked it," she said.
One of the hardest and oldest technologies is tintype, a complicated and somewhat touchy technique invented in the mid-1800s.
Also called wet-plate photography, tintype involves coating a metal plate with collodion, a syrupy solution of cellulose nitrate dissolved in ether originally used to dress wounds. When the plate is dunked in a bath of silver nitrate, the surface becomes light-sensitive. The plate is then put into a holder and inserted into the back of a large-format camera.