Daguerreotypes can be restored by skilled conservators, although this may not always be advisable, as the images are very fragile and there is always some risk of damage.
Preservation can be aided by the replacement of the matt and glass. However, the original glass contributes to the look of the object and is often retained. Layers of clear mylar can be used between matt and glass and behind the plate, together with improved sealing. The Library of Congress web site (see Resources) gives some detail on their approach.
