PREAMBLE
The Daguerreotype is a paradox: even if it is the most fragile among all the photographic medias, it is very common to find some of them aged of more than a century and a half and, in a pristine stage of conservation.

Unfortunately, other ones are is a poor shape; this is the case of many French daguerreotypes. Fading portraits without contrast, the surface is scratched or tarnished, some oxydation areas are visible, etc...

GOLDEN RULES
If you must remember something, it must be these three points :

MAIN CAUSES OF DAMAGE OF A DAGUERREOTYPE
The daguerreian image is inscribed on a thin plate in copper which has been covered of a silver layer (3%), then polished such as a mirror before being sensitized according to the process described by Daguerre.

The daguerreian image inscribed on the surface of the silvered copper plate is extremely sensitive to the external attacks. The air humidity, dusts, brush, nails, finger prints... even the slightest contact with the image is enough to immediately induce tarnish or scratch, unfortunately irremediable.
In order to avoid such a risk, the daguerreian image must be always covered with a cover glass with which it must remain interdependent and sealed.
 

This is a frequent issue and the resulting damages remain visible even after all required measures have been taken. When the cover glass is broken, its parts remain in place due to the sealing paper which hold them together, giving a false feeling of protection.

Due to the friction between the glass parts, a microscopic glass powder will settle along the glass fissure and abrade the surface of the image. Air and dust will also rush into this crack and induce tarnish.

More insidious are the damages linked to the nature of the old glasses used for protection. With the passing years, some bubbles of solvent resulting from the glass deterioration, appear in its structure. When they explode, these solvent fumes are inducing on the surface of the image, a tarnish spot which will enlarge itself with time.

REPLACEMENT AND RESEALING OF A COVER GLASS
Very often, the replacement and resealing of its cover glass are enough to stop the causes of the progressive deterioration of a daguerreotype. In addition, the general cleaning of the dag that is done at the same time, conducts to a spectacular improvement of its look.

     1. a bottle of distilled water
     2. air spray for dust removing  
     3. a decimetre
     4. archivist gloves
     5. a towel made of 100% cotton
     6. a container
     7. a roll of Filmoplast ® P90 2 centimeters wide (*)
     8. the daguerreotype to be repaired
     9. two spring clips
    10. a pair of scissors
    11. a flat knife (not represented)

     (*)  The Filmoplast P90 is available in all good stationeries and is chemically neutral.
          Avoid common scotch tapes which are totally inappropriate for the restoration purpose as they contain solvents and acids.

The aim is to remove the daguerreotype from its environment of display.

If the dag is French (see on the left), it is generally presented with a maroon or blue passe-partout, decorated with a golden edging, and mounted within a frame of black or gold color and in a Napoleon III style. As these frames are quite rare, it is recommended to take care about them during the dag removal operations.

If the dag is American or English (see on the right) , it is presented with a brass mat and displayed in a special case decorated with velvet. Other presentations are also possible : wooden frame in Japan, cardboard frame in Mexico, etc...

Remark : when it exists, a passe-partout is always taken in a sandwich, between the daguerreian image and the protection glass.

In order to remove an American or English dag from its case, we usually use a thin strip. You must be very careful not creating a too excessive pressure in order to not break the cover glass or the edges of the case.

Some daguerreotypes, especially American ones, have an additional brass frame which hides the paper ensuring the sealing of the daguerreotype. In order to remove this brass frame, gently straighten out its borders as indicated on the opposite photography.

 

 

When the dag has been removed from its frame or its case, it is possible to precisely measure the size of its cover glass. Even if the sizes of dags have been standardized, it is frequent that these ones do not match the expected dimensions... Due to this, it is safer to take yourself the exact measures of the cover glass which needs to be replaced.

You must be very careful when doing that; if not, you are taking the risk to impact the quality of the sealing and more, to face the impossibility to replace the dag back into its original frame or case.

When you will visit your mirror dealer, ask him to cut a new cover glass having the exact dimensions you have measured. The glass must be of an extra-clear and non-reflecting quality and having 2 mm thick.
Important, for security reasons, ask the dealer to sand down the cutting edges of your new cover glass.

 

When you have your new cover glass, you must clean it to remove all traces (i.e finger print) from its surface. Absolutely proscribe the use of any alcohol-based product used for glass cleaning. They may damage the surface of your precious dag.

Wash your new cover glass under the tap water. Put neutral soap on its two sides and scrub it with your fingertips or a clean sponge. When you think the glass has been cleaned enough, hold it by its edges and rinse it under the tap water.

Still holding the glass by its edges, immerse it in container that you will have first filled with distilled water. Do not drop the glass into the container but gently move it into the bath to ensure its two sides will be efficiently rinsed by the distilled water.

Take out the cover glass from its bath holding it by its edges and dry it with the towel made of 100% cotton. Check if all the traces have disappeared from its surface; if the result is not satisfactory, do not hesitate to redo the whole process of cleaning from the beginning.

When the new cover glass appears cleaned enough, put it back on its edge in a clean and dry location.

Did you ever think about the emotion of the egyptologists who proceeded for the first time to the removing of the wrapping of a mummie ? That is exactly what you will feel at that point !
Facing such situation, your hands may become sweaty... If that is the case, it is time for you to put your archivist gloves.

Remove the old glued paper from the back of the copper plate. Don't think that because this paper is aged of one century and a half, it will not resist too much. Some times, this is exactly the case, the old seals just crumble in your hands as you touch them with your fingers. 

However, sometimes the exact opposite is true: the glue holding the paper is completely intact, and the paper seals are adhering to both the edge of the glass and to the back of the dag as though they will never let go. In such a case, you have to cut through the edge of the package using both hands and a flat knife. Carefully control how much of the tip of a the flat knife you are allowing to penetrate the paper seal as you cut around. 

When you are feeling that the cover glass is no longer fixed to the daguerreian image, remain focused on this last one as it is clearly the most fragile part. Move away the cover glass and the passe-partout or the brass mat. During all this operation, pay a lot of attention to always hold the copper plate by its edges and ensure that your fingertips never touch the daguerreian image.

Proceed like for the new cover glass : secure the daguerreian image in a clean and dry location, being sure it is resting on its edge in order to reduce the surface offered to flying dusts.

Before resealing together the daguerreian image, its passe-partout and its new cover glass, you must proceed to the dusting of the different items. Don't worry, this is a more meticulous step than really a difficult one.

First, you must ensure that no draft is disturbing the atmosphere of the room. If a window is open, close it.
Using the air spray fitted with its extended diffuser, remove the dust from the internal side of the cover glass (the one which will be in contact with the daguerreian imahe), then pursue with the two sides of the passe-partout or the brass mat, achieve this operation with the daguerreian image itself.

                     1. dusting of the cover glass                  2. dusting of the passe-partout or the brass mat       

3. dusting of the daguerreian image

Proceed with long and continuous spraying, moving always in the same direction, from top to bottom.
Caution ! During spraying, the pressure of the gaz will decrease as well as its temperature. So it is important to always keep the end of the diffuser at a distance of 2 inches from the surface of the image to not freeze this one. This phenomenon is without effet for the cover glass but may damage the surface of the daguerreian image.

When they have been dusted, keep the cover glass and the passe-partout (or the brass mat) close from you but keep them resting on their edges in order to reduce the surface offered to flying dusts.

If you have followed the explanations provided in step #6, you must have your daguerreian image in your hand. Position your passe-partout (or brass mat) over the daguerreian image while ensuring they remain not yet in contact. 

Check if the passe-partout (or the brass mat) stands at its exact location over the image. If you are satisfied how it looks then, flatten the passe-partout on the daguerreian image. To that point, your fingers must ensure a sufficient pressure on the edges of the two parts (the cover glass and the copper plate) in order they can not slide one over the other as it would damage the daguerreian image.

With your free hand, use the air spray on this set in order to remove the new dusts which could have reappeared onto its surface.

Take the cover glass and flatten it onto the passe-partout or the brass mat. Ensure to apply the dusted side of the cover glass on the passe-partout or the brass mat.

To that point, you must check again if new dusts are not infiltrated under the cover glass. If it is the case, release the pressure of your fingers in order to let the cover glass moving apart a little. Then, chase away the eventual dusts with another spraying and replace the cover glass onto the rest of the package.

Now, your fingers are immobilizing the 3 parts for a while, holding them by theirs edges. You probably feel the numbness coming...

Do not panic ! That is here that the two spring clips will help. Apply the first one on the top of the package and the second one on its bottom. Proceed carefully, not releasing the spring clips too quickly as it may damage the cover glass. When the two spring clips are in place, you can release your fingers.

 

Because the next 100 years of the life of your dag will depend from the quality of its making, this step is very important. The purpose is to ensure that the package made of : the daguerreian image, its passe-partout and the cover glass remain linked together and perfectly sealed to avoid infiltration of air.

Cut a strip of Filmoplast ® P90 of a lenght a little longer than the dimensions of the dag to be sealed. Caution, this strip must remain in one part, and not cut in several ones, as its laying must be uninterrupted. The Filmoplast is no more than a neutral (solvent free) scotch tape with a sticking face protected with a film. It is not suitable to totally peel this protective paper before proceeding to the sealing of the dag as the sticky side of the Filmoplast would autoglue to itself during the operations.

Peel the protection film from the Filmoplast on approximately 5 inches and apply its sticky part on the edge of the glass, starting from one corner and leaving a surplus of film. Ensure the Filmoplast does not cover the glass more than 2 mm at maximum.

This kind of sealing differs from what was made in the past. At that time, the glued paper used to seal the daguerreotype was not coming over the cover glass but was just in contact with the edges of this one.

When the strip of Filmoplast has been positioned on the entire side, make a turn on the next side and let the rest of the strip hang down into the void. Pull down the Filmoplast onto the back of the cupper plate, starting from the corner you started from. While pulling down the Filmoplast, apply some tension on the film to ensure a better sealing of the package.

 

When the first edge is done, move the spring clip to the edge which is facing the one you just seal. Then, peel the protective film from the Filmoplast on another 5 inches and reiterate the same process as describe before.

The folding of the Filmoplast in the corner of the daguerreotype requiers some practice to obtain an acceptable result. The folding of the Filmoplast must be at 45° for an attrative aspect.

Proceed like this for the four edges of the package. Complete the sealing by pulling down the surplus of Filmoplast you have secured at the beginning of the operation.

 

On the back of the dag on the resealing tape, write the date of the day as well as the different operations of restoration you have done (new cover glass, cleaning, etc...). Be sure to use a very soft, lead pencil only .  This is because a ball-point pen, and even a hard-lead pencil, can actually dent the dag plate because too much pressure is put onto the writing instrument tip and it presses down into the plate surface (unintentional, for sure, but it really happens) and pushes the plate surface up on the other side.
If it is a US or English daguerreotype, reinstall the brass frame which must exactly hide the portion of the Filmoplast which remains visible on the cover glass. At that point, you will realize why the fold of Filmoplast must have 2 mm at maximum!).

   

Using the towel made of 100% cotton, and of course without any alcohol-based product used for glass cleaning, clean the cover glass to remove any eventual remaining fingerprints. Finally, reinstall the daguerreotype in its case or frame.
It's over. Your daguerreotype is now ready to face the next 100 years !