Consolidation of Lifted Emulsion

From Conservation of photographic negatives

Every consolidation treatment should contain a preceded cleaning of emulsion and emulsion-base-interface, possibly by a solvent bath.^[1]

Preliminary duplication or at least photographical documentation is recommended.

[edit] Collodion Emulsion

Lifted collodion emulsion can be consolidated in a vapor chamber in an atmosphere of 60% ether, 40% alcohol and 2ml camphor^[2] ^[3]
Another option can be to cover the negative with a covering glass and fixing the whole package with acrylic tape along the edges leaving some gaps for evaporation of degradation gases.^[4]

[edit] Gelatin Emulsion

To consolidate lifted gelatin emulsions the flakes must be relaxed since mostly they are rolled up. At the same time changes of the dimensions during fixation of the flakes by swelling or shrinking must be avoided. The consolidation method shouldn’t change any properties of the gelatin emulsion like transparency or similar.

Protection varnishes or other coatings can get affected by humidity or alcohol by getting a white appearance.^[5]

Mostly non-aqueous systems are recommended to avoid uncontrolled swelling of the gelatin: here Acryloid (Paraloid) B-72 and Klucel G seem to be the only ones that are tested appropriate in terms of long term durability and stability.^[6]

Disadvantage: with non-aqueous adhesives it’s not possible to relax curled gelatin emulsion.^[7]

The use of aqueous solutions containing gelatin is not recommended since it was found that after treatment the lifting was more severe than before due to swelling and subsequent shrinking of the gelatin emulsion, besides it was difficult to attain appropriate adhesion since the glass base couldn’t be cleaned well enough.^[8]

For small emulsion flakes (e.g. along the edges) it can be appropriate to use a solution of demineralized water containing 5% of gelatin applied by a small brush.^[9]

Especially the consolidation of large emulsion flakes is problematic. One treatment is published which uses a very thin pellicle of gelatin placed between lifted emulsion and glass.

For this the pellicle is prepared by solving 10% gelatin in 40°C warm demineralized water, the solution is spread on polyethylene film using a film applicator (Sheen).
The pellicle is dried at 23°C and 50% relative humidity and cut into pieces of the format 1 x 1 mm.
The dry pieces are placed underneath the lifted emulsion and reactivated with a drop of water or water vapor. Now the emulsion can be fixed.
Additionally a cover glass can be placed on top of it preventing direct contact by a thin frame of polyester film.

This method is kind of reversible.^[10]

Another method combines humidity for relaxation with a non-aqueous adhesive.^[11]

A thin layer of Acryloid (Paraloid) B-72 (5% in xylene) is applied to the glass underneath the lifted emulsion.
Locally the lifted emulsion is humidified by an ultrasonic nebulizer that it relaxes and lies down.
The glass plate is left over night in a humidity chamber to let the Acryloid dry (this step is not essential as further testing showed).
The edges of consolidated flakes can be additionally fixed afterwards by using a thin solution of gelatin (1-2%)

Disadvantage: after drying of the emulsion gaps between the consolidated flakes open up, so duplication in wet condition is recommended.

A general problem with delaminated gelatin plates is to attain appropriate adhesion between organic coatings like the gelatin and inorganic surfaces like the glass. The use of an adhesive can lead to changes of the emulsion in terms of reflection and transmission. Thus a treatment is published using organosilanes as a suitable bonding agent between organic and inorganic materials for consolidation.^[12]

Lifted emulsion can be lain down by placing a cardboard of the plate format bit by bit on top of it, folded emulsion should better be left folded, the whole package gets fixed by an adhesive tape along the edges and then placed in an archival flap^[13]

A glass plate sandwich can be helpful to duplicate negatives with lifted emulsion^[14]

Cracked but not yet lifted gelatin emulsion can be stabilized by an additional gelatin coating on top of it.^[15]

Formulas for gelatin solutions are

Mix a tablespoonful of gelatin with ¼ cup of 50°C warm distilled water, then add ¼ a tablespoonful of ammonium hydroxide and ¼ a tablespoonful of photo-flo (1:200 in water)
Mix 5g of gelatin with 5ml photo-flo (1:200 in water), then add 0,5g chrome alum and 500ml 55°C warm distilled water (this is a more durable solution since the gelatin is hardened)