Emulsion Transfer with Film Negatives
From Conservation of photographic negatives
| Conservation Treatments |
To separate the emulsion from film bases either the substratum or the substratum together with the base itself is dissolved.
Thus it’s a very drastic and risky treatment and should only be considered if there’s no other possibility to preserve the image.
In every case all negatives treated in this way should be duplicated or documented by reference slides first.
- use trays made of glass, metal or enamel, most plastics are not solvent resistant.
(REED, V.L., 1981)
- hardening of the emulsion before separation in vapors of formaldehyde for 10 minutes is possible.
(GILLET, MARTINE; GARNIER, CHANTAL, 1989)
- after separation of the emulsion it can be transferred to a new base or flattened and stored separately.
Contents |
[edit] Formulas for different kinds of base material
- Method used by Chicago Albumen Works
(MUNSON, DOUG, 1997)
- Stripping bath of methanol and acetone (1:1) over night to separate the emulsion
- Cleaning of the emulsion by a bath of MEK for 1 hour and
- Two sequent bathes of fresh solution of methanol and acetone (1:1) to dissolve all residues of substratum
- Two sequent bathes of ethanol and water (95:5) to relax the emulsion, 24 hours in the first bath, afterwards placing the emulsion on a temporary barrier like polyester, directly before flattening into the second bath (which is free of methanol and acetone residues)
- Placing the emulsion (face up) onto a vacuum contact frame under exhaust system, covering it by a sheet of polyester (recommended 0.6 mil)
- Striping out the remained alcohol by a cloth or similar
- Small pieces of emulsion can still be moved to the right place through the polyester sheet
- The package can now be duplicated or the emulsion prepared for archiving: thereto the upper polyester sheet together with the emulsion is lifted and placed on archival paper twice as the format as the emulsion, the polyester sheet on top is slightly rolled up, the emulsion held by two corner. The second half of the archival paper is folded on top of the emulsion, the whole package is dried over night between blotting paper and under weight.
It’s recommended to plan the working procedure with higher amounts of negatives, from the first step to the last every negative takes 3 days. Every bath should be filled. The emulsions are relatively stable as long as they are staying in the bathes, if an unscheduled interruption occurs.
Negatives made by Kodak or Defender mostly are easy to separate, with Agfa or Ilford it can be more difficult.
Advantage: cost-effective method, which is also suitable for high amounts of negatives
- Bath of MEK for all negatives except cellulose triacetate since it shrinks in MEK, therefore methyl acetate should be used.
With nitrate negatives the AC-layer can be removed to enable better contact of the MEK, This is done by small amounts of warm water and slight friction.
To prevent the emulsion from too much curling during the bath the negative can be placed between two sheets of paper or a temporary second polyester film can be added. Relaxing of the emulsion and removal of folds in a water containing bath of MEK.
(WOODS, CHRISTOPHER, 1992)
- At all edges of the negative a thin stripe can be cut off to enable the solvent to reach the substratum
Bath of water, methanol and acetone (1:4:5) for 15 to 60 minutes, the emulsion should flow off, slight mechanical assistance possible
(GEAR, JAMES L. ET AL., 1977)
- For strongly warped negatives the following is recommended:
Bath of 25-28°C warm water for 1 to 3 minutes, then bath of methanol and acetone (45:55) for 3 to 5 minutes, emulsion should flow off.
(GEAR, JAMES L. ET AL., 1977)
- The following treatment is recommended if large quantities or a whole collection of negatives must be treated without that much value of the single piece.
(PAVELKA, KAREN L.; NAIPAVEL-HEIDUSHKE, VICTORIA, 2005)
- Negative is placed emulsion side down on a sheet of Mylar
- bath of ethanol, acetone and water (1:1:1) covered for approximately 2 hours (the acetate base becomes milky and falls apart)
- package of negative and Mylar is placed on a light table (the emulsion kept damp by spraying the separating solution on it)
- pieces of the base can be removed by tweezers, residues of base and substratum can be removed by brushing some fresh solution on the emulsion and using tweezers
- Turning of the emulsion by placing a second sheet of Mylar on top of it.
- The emulsion is dried between polyester mats under blotting paper and weight for at least 24 hours.
- After drying residues of the substratum can be removed by cotton swabs saturated by acetone.
- Package of mats and emulsion is placed in a polyester envelope, the mats can be pulled out.
- Scanning and duplication is possible without removing the envelope.
Disadvantage: emulsions can get tears and warping, residues of the substratum are visible, the emulsion can expand
Advantage: suitable for mass treatment (time for one negative approximately 12 to 35 minutes), non-toxic solvents
[edit] General disadvantages
- Methanol can weaken the emulsion and is very toxic.
(WOODS, CHRISTOPHER, 1992)
- It was found that methanol and acetone cause dimensional changes in the emulsion (methanol causes swelling, acetone shrinking), the least changes are caused by MEK
(BORTFELDT, MARIA, 2000)
- After treatment with methanol residues of substratum can be found on the emulsion, acetone can cause a white haze
(BORTFELDT, MARIA, 2000)
- With water content of 10% and higher the gelatin swells and looses its dimensional stability, becomes sticky and fragile, the risk of silver migration is given. Water content of working solutions can rise due to uptake from the surrounding humidity or by faster evaporation of ethanol. It’s recommended to work in a relatively dry environment (35% or less) and if possible not to carry out these treatments during summer time.
(MUNSON, DOUG, 1997)
[edit] Special formulas for cellulose nitrate negatives
- Bath of methanol (95% + 2,5% v/v water)
(REMPEL, SIEGFRIED, 1977)
- Method by Reed
(REED, V.L., 1981)
- Negative is placed emulsion side down onto a glass plate, it got fixed to it by adhesive tape along the edges (solvent resistant like Scotch No. 850 or 853)
- The back coating is removed by 5% sodium hypochlorite (white foam is formed which can be wiped off)
- Bath of MEK softens the cellulose nitrate base which can be scraped off by a piece of cardboard
- Residues are removed by a cotton ball soaked by MEK
- The tape is removed, the covered edges cut off
[edit] Special formulas for cellulose diacetate negatives
- At all edges of the negative a thin stripe is cut off to enable the solvent to reach the substratum, then bath of MEK for 3 to 4 minutes, subsequent bath of photo-flo 200 (1:10 in 24°C warm water) is possible if the emulsion doesn’t separate in the first bath
(REED, V.L., 1981)
[edit] Transfer to a new base
It’s possible to archive the emulsion between layer of archival paper and cardboard without transferring it to a new base, this is recommended since transferring to a glass base would create new problems related to the material glass and the transfer to a polyester base is time consuming and expensive.
(MUNSON, DOUG, 1997)
If the emulsion is to be transferred, there are several techniques and materials.
- Method by Reed
(REED, V.L., 1981)
- A gelatin coated sheet of polyester (like Kodak Roller Transport Cleanup Film 4955) can be used, taped onto a glass plate, the emulsion placed on top of it.
- Some drops of photo-flo in water (1:10) help to relax and place the emulsion (heavy folds can be treated with water vapor).
- A protection layer can be placed on top of it by the dry emulsion of a fixed and washed Translucent Stripping Film. This emulsion is squeezed on by a rubber roller working from the center to the edges
- Emulsion is placed face down onto a sheet of polyester and flattened by adding some photo-flo in water (1:2000). The new base (Kodak roller transport film 4955) is coated on both sides with two sequent gelatin solutions (1. 1% gelatin, 0,1% chrome alum, 2. 4% gelatin). This base is placed on the emulsion.
(GILLET, MARTINE; GARNIER, CHANTAL, 1989)
- The emulsion still swimming in an aqueous bath is let lie down onto a gelatin coated glass plate or developed and fixed sheet of film. The emulsion is brought into the right position and vertically dried
(WEINSTEIN, ROBERT A.; BOOTH, LARRY, 1977, p 194)
[edit] Temporary solutions
- The wet emulsion is placed onto a wet sheet of Mylar and covered by a second one. The package is squeezed out by a rubber roller and can be duplicated.
(GEAR, JAMES L. ET AL., 1977)
- The wet emulsion can be squeezed onto a glass plate by a rubber roller for duplication
(BORTFELDT, MARIA, 2000)
[edit] References
- BORTFELDT, MARIA, 2000. Ein Restaurierungsverfahren für Cellulosenitrat- und acetatnegative. Rundbrief Fotografie, 7 (4), 8-12
- GEAR, JAMES L. ET AL., 1977. GEAR, JAMES L. ; MacCLAREN, ROBERT H.; McKIEL, MARY. Film Recovery of Some Deteriorated Black and White Negatives. The American Archivist, 40 (3), 363-368
- GILLET, MARTINE; GARNIER, CHANTAL, 1989. Les négatifs sur support en di-acetate de cellulose. Nouvelles de l'Arsag, 5, 4-5
- MUNSON, DOUG, 1997. The pellicular burlesque. Topics in Photographic Preservation, 7, 55-65
- PAVELKA, KAREN L.; NAIPAVEL-HEIDUSHKE, VICTORIA, 2005. A Step in the Evolution of the Treatment of Acetate Negatives. Topics in Photographic Preservation, 11, 17-24
- REED, V.L., 1981. How to Work Restoration Magic on Wrinkled Negatives. Photographic Conservation, 3, 4-6 (reprinted from Professional Photographer, July 1980)
- REMPEL, SIEGFRIED, 1977. A Conservation Method for Nitrate Based Photographic Materials. The Paper Conservator, 2, 44-46
- WEINSTEIN, ROBERT A.; BOOTH, LARRY, 1977. Collection, Use, and Care of Historical Photographs. Nashville: American Association for State and Local History
- WOODS, CHRISTOPHER, 1992. Negatives: Positive action. In: The Imperfect Image; Photographs their Past, Present and Future, 6th -10th April 1992, Windermere, 323-327
