Depending on conditions, the rates of deterioration of the materials that make up a daguerreotype package (e.g., copper, silver, paper, brass, leather, velvet, silk and glass) can vary substantially. One of the most common problems found by conservators is glass deterioration.
Glass deterioration often makes the daguerreotype appear dull and hazy. This does not necessarily mean that the plate itself has deteriorated. A number of the daguerreotypes from the Library and Archives Canada (LAC) collection that were prepared and treated for exhibition showed distinct signs of glass deterioration
Glass deterioration can occur as a result of fluctuations in either temperature or humidity. There are a couple of ways in which this type of degradation can manifest itself. One is cracking, which is when tiny hairline cracks appear on the surface of the glass. The other is chemical decomposition, which affects older glass with a higher concentration of sodium oxide, causing the glass to appear hazy or cloudy.
Keeping the original glass of a daguerreotype is always encouraged, and in cases where the glass is in an early stage of deterioration, e.g., it appears hazy or foggy, it can possibly be cleaned and reused. Treating this type of deterioration is relatively straightforward: the glass is removed, cleaned with distilled water and a neutral soap, rinsed with ethanol, then left to air dry. When placed back onto the daguerreotype, the plate will immediately appear brighter and clearer. Continue reading