Observing Preservers
Preservers. Not exactly Life Preservers, but in a sense serving the same purpose. In case mounted images, such as daguerreotypes, ambrotypes, and early tintypes, the preserver was a thin brass (or more specifically, ‘pinchbeck’) element, folded around the edges of the image, cover-mat, and glass cover.
How would such a contrivance ‘preserve’ the image? Well, when removing the three components (or, rarely, two) from the case, the preserver holds the three together, so they do not slide about and scratch the image.
The preserver would also help hold the image more securely in the case, I suppose. It might help further restrict the flow of air over the surface of the image as well, slowing the chemical degradation such as tarnishing, that is dependant on oxygen — but it was far from being a hermitic seal.
Those who have studied daguerreotype cases cite the absence of preserver as an indication of early provenience, specifically 1839-49 (of photographic images, only daguerreotypes were placed in cases in those years). After that, preservers were supposed to be ’simpler’ in design 1850-55, and more ornate after 1855. Most ambrotypes and early tintypes date from 1855 or later, so they usually have the more ornate preservers. Nobody defines exactly how to distinguish ’simple’ from ‘ornate’ — so in this study we distinguish four levels of complexity, describe and define each, and look at the temporal distributions for each.