I just acquired my first half-plate daguerreotype. Half-plate is roughly 4.25 x 6.5 inches in size. Daguerreotypes get truly impressive once they exceed 1/4 plate size. In the second photo of the plate alone, you can clearly see the delicate hand-coloring of his face and hands and the tablecloth on the table to his left in the photo.
This is the plate as it was delivered. It has the original heavy flint glass installed (2.5mm thick!), and you can clearly see the dust and other schmutz on the inside of the glass. It did have its original paper seals, but they were in poor condition, having broken in some places. The preserver looked to have never been opened, either (the preserver is the gold-colored copper foil border around the image that further seals the edges). I decided to open the preserver and examine the state of the seals, to see if it was worth breaking them to clean the glass.
You can see the seals themselves on the left- after a century and a half, the cheap paper tape with a most likely acidic glue was in very poor shape, and not sealing the plate at all. I removed the seals and cleaned the glass. I have temporarily (until I can get a replacement piece of modern borosilicate glass) reinstalled the original flint glass. The reason for replacing the glass (I will keep the original glass with the plate for reference) is that part of the reason the schmutz was on the inside of the glass plate was that the glass itself had impurities and weaknesses that allowed moisture to migrate to the inside of the packet over time. Putting the original glass back on the packet and sealing it up would be undermining your preservation efforts.
When the new glass arrives I’ll replace it and re-seal it with Filmoplast P90, an archival tape, and back the plate with a sheet of acetate for additional protection. At a later date I’ll have the plate professionally cleaned.
Cleaning the glass and re-sealing the packet are restoration activities I feel reasonably confident in my skills to perform. Cleaning the actual plate is something currently way beyond my skills and knowledge – it’s one thing to putter around with modern, reproducible, replaceable objects, another thing entirely to attempt cleaning on an unique original a century and a half old that if damaged or altered is effectively lost forever.