Topic: Ambrotypes - Images on glass
Ambrotypes became popular in New Zealand in the mid 1850s. They look similar to daguerreotypes, but the images were made on glass plates. The plates were coated with a substance called collodion, then dipped into silver nitrate to make a light-sensitive surface.
Compared with daguerreotypes, both sitting for and processing an ambrotype photo were easier. Sitters had to remain still for less time for the photo to be taken, and the process of developing the image was more reliable. It was still only a one-off image, though, and still quite expensive.