ACRL News Issue (B) of College & Research Libraries September 1 9 9 7 /5 6 1 Care of photographs By Gary A lb righ t The right en viro n m en t a n d proper storage are critical “Behold thy portrait! — day by day, I’ve seen its features die; First the moustachios go away, Then off the whiskers fly. That nose I loved to gaze upon, That bold and manly brow, Are vanish’d, fled, completely gone Alas! Where are they now?… ” So lamented a poet in an 1847 issue of Punch less than 10 years after the invention o f ph o ­ tography. The same could b e w ritten about many of today’s photographic images. People have been concerned about the perm anence o f photographs for more than 150 years. Over that time, dozens of photographic processes have been used. Each has its ow n unique dete­ rioration characteristics and, therefore, its ow n specific storage and exhibition needs. However, there are com mon factors affecting the perm a­ nence o f all photographs. By controlling these factors, the deterioration of a photograph can be slowed, and its longevity greatly enhanced. Control temperature and relative humidity Control o f tem perature and relative humidity (RH) is critical to the preservation o f photo­ graph collections. Heat accelerates deteriora­ tion: the rate of chemical deterioration of most p h o to g r a p h ic m a teria ls is a p p ro x im a te ly doubled with each 10°F increase in tem pera­ ture. High relative humidity provides the mois­ ture necessary for harmful chemical reactions leading to much o f the fading, discoloration, and silver mirroring visible in photograph col­ lections. High relative humidity in combination with high temperature encourages mold growth and insect activity. Extremely low relative hu­ m id ity m ay le a d to d e s ic c a ti o n a n d embrittlement of certain photographic materi­ als, as well as curling of photographs or flak­ ing of glass plate emulsions. Excessive fluctuations in tem perature and relative humidity are also damaging. These may lead to structural damage within photographs, such as cracking of emulsions or w arping of photographic supports. Tem perature should be maintained at 70°F or below. In general, the lower the tem pera­ ture, the better. An often recom m ended com­ promise betw een storage needs and staff com­ fort is 65°-70°F. Areas u sed exclusively for storage should be kept at a low er temperature. Relative humidity for a mixed collection of pho­ tographs should be maintained betw een 30 per­ cent and 50 percent with fluctuations less than 10 percent a day. Storage at the low end of the RH range rather than at the higher end can significantly improve the long-term stability of several photographic processes. Cold storage is often recom m ended for particularly vulner­ able materials such as color photographs, ni­ trate film, or safety film. W hen materials are taken out of cold storage, they should be placed in a plastic bag and allowed to acclimate to room conditions before use. This avoids p o ­ tential condensation and w ater on the cold sur­ faces of the materials. Temperature and humidity can be controlled using various forms o f climate-control equip­ ment. W hen such equipm ent is not available, there are still simple measures that can be taken to moderate environmental conditions. Avoid Gary Albright is senior conservator a t Northeast D ocum ent Conservation Center (NEDCC); e-mail: garya@nedcc.org. This article has also been published by NEDCC as one o f its technical leaflets that are made possible by a g ra n t fr o m the N ational E ndow m ent f o r the H um anities. The complete collection o f technical leaflets is available as Preservation of Library and Archival Materials: A M anual. Contact the A m erican Association o f M useum s to order a t (202) 2 89-9127 mailto:garya@nedcc.org 5 6 2 /C&RL News using attics (too hot) or basements (too damp) for storage areas. Often an interior room or closet offers the best environment. Collections should be kept off the floor, w here they are more likely to be dam aged by insects or w a­ ter. D on’t hang or store photographs on exte­ rior walls, in bathrooms, or over heat sources such as fireplaces, radiators, or heating vents. Keep heat low in the winter, and encourage the staff and visitors to w ear warm clothing. Seal w indow s and doors to minimize exchange o f outside air. Store photographs in folders, boxes, or cabinets; this moderates the effects of environmental fluctuations. The use o f air conditioners, dehumidifiers, and humidifiers can also be helpful. However, make sure that such equipm ent is improving conditions and not causing them to worsen. For example, air- conditioning can actually raise relative humid­ ity under certain circumstances. Control air pollution and dirt Pollutants and particulate matter can damage photographs, causing fading or abrasion. Air purity is especially a concern in an urban envi­ ronment. Controlling air quality is difficult. Ideally, air entering a storage or exhibition area should be filtered and purified. Dust should be kept to a minimum. Gaseous pollution can be re­ m oved by chemical filters or w et scrubbers. Particulates can be mechanically filtered. Good air circulation is also necessary. Make sure air intake vents are not located near loading docks w h ere trucks idle. K eep exterior w indow s closed w hen possible. Also, minimize interior sources of harmful gases. These include ph o ­ tocopying machines, many construction mate­ rials, paint fumes, cardboard, carpets, and jani­ torial supplies. Metal cabinets are preferred over w ood, as w ood often generates harmful per­ oxides. Finally, keep photographs in archival- quality enclosures. Enclosures k eep dirt off objects and may help decrease the effects of pollutants. Enclosures containing activated char­ coals and molecular traps have recently b e­ com e available and appear to be effective in this regard. Control light levels Light causes embrittlement, yellowing, and fad­ ing in photographs. Light damage is cumula­ tive and usually irreversible. Direct sunlight is the most harmful light source; incandescent (tungsten) lighting is generally preferred to fluo­ rescent. However, all forms of light are dam ag­ ing and should be moderated. Do not place valuable photographs on per­ manent display. Use copies w henever possible (color laser copies are an inexpensive, readily accessible alternative) and keep light levels as low as possible. Avoid hanging photographs w here they will be exposed to daylight, espe­ cially direct sunlight, or to unfiltered fluores­ cent lights. Both of these light sources gener­ ally g iv e o ff h ig h a m o u n ts o f d am ag in g ultraviolet (UV) light. UV-absorbing sleeves can be used to filter out damaging rays from fluo­ rescent tubes, and UV-absorbing sheets can be placed over windows or in frames. Also, low- UV-emitting bulbs are now available. Be aware that certain types o f photographs are much more susceptible to light damage than others. Most color photographs fade rather quickly on display, while contemporary fiber-base black- and-white prints are essentially stable. Exhibi­ tion of 19th-century photographs should be lim­ ited and carefully controlled. Control handling Fingerprints can cause chemical dam age to photographs, resulting in bleaching or silver mirroring. Careless handling can cause physi­ cal dam age such as abrasion, tears, or break­ age. Use clean gloves or clean, dry hands w hen­ ever photographs are handled. D on’t touch photographic emulsions. Handle photographs carefully. Proper enclosures (sleeves, albums) provide protection from fingerprints and physi­ cal support to protect against abrasion or break­ age. W henever possible, avoid handling alto­ gether by providing users with photographic duplication or photocopies. If photographs must be labeled, labeling should be done on the reverse along the edge. In most cases, ordinary lead pencils are recom­ mended. Where lead pencils do not work (such as with RC prints), black india ink is recom­ m ended. Koh-I-Noor Black Rapidomat Ink No. 30740-F in a hollow-point technical p en ap­ pears to work particularly well. Control storage systems Proper storage materials are essential for the long-term stability of photographs and nega­ tives. They provide m uch-needed physical sup­ port and protection for fragile objects, and at the same time act as a barrier betw een the ph o ­ tograph and a potentially unstable environment. It is of utmost importance that storage materi- September 1 9 9 7 /5 6 3 als be unreactive to the photographic material. Much dam ag e has b e e n d o n e in th e p ast through the use of reactive materials such as acidic g ro u n d w o o d p a p e r sleev es, ru b b er bands, paper clips, pressure-sensitive tapes, and staining adhesives such as rubber cem ent or animal glue. All enclosures used to house photographs should m eet the specifications provided in the American National Standards Institute (ANSI) Standard IT9.2-1991, and should have passed the Photographic Activity Test (PAT) as speci­ fied in ANSI NAPM IT9.16-1993 • The first stan­ dard provides specifications o n enclosure for­ mats, papers, plastics, adhesives, and printing inks. The PAT has two components: a test to detect image fading resulting from harmful chemicals in enclosures, and a test to detect staining reactions betw een enclosures and gela­ tin. Consumers should contact their suppliers to see if their products have passed the PAT. When storing photographs it is best for each object to have its ow n enclosure. This reduces damage to the photograph by providing it with physical protection, support, and isolation from any dam aging com ponents o f oth er p h o to ­ graphs. Prints and negatives should not be in contact with each other in the same enclosure. Acceptable enclosures may be made o f either paper or plastic. P a p e r e n c lo s u r e s : • are opaque. This protects objects from light, but may result in increased handling for viewing. • are porous. This protects the object from the accumulation of moisture and detrimental gases. • act as a buffer against changes in humid­ ity. • are available in buffered and nonbuffered stock. Choosing betw een the tw o is not the crucial issue it was once thought to be. In most cases conservators prefer nonbuffered material, but buffered enclosures are usually recom ­ m ended for storing nitrate negatives and early safety film. • should not be m ade of kraft or glassine paper. P la s t ic e n c lo s u r e s : • are tran sp a ren t. P h o to g ra p h s can be viewed without removal from the enclosure, thus reducing handling. • can trap moisture and cause ferrotyping (sticking, with a resultant glossy area). • should be m ade o f uncoated polyester, polypropylene, or polyethylene. Soft polypro­ pylene an d low -density polyethylene (both used in ring-binder storage pages) have addi­ tives or coatings that cannot be properly evalu­ ated. • s h o u ld n o t b e m a d e fro m p o ly ­ vinylchloride (PVC). • should not be used to store nitrate or older safety film negatives, as this will hasten their deterioration. Avoid using adhesives that may cause chemi­ cal damage. Adhesives that are particularly dam­ aging include rubber cement and the self-stick “magnetic” pages of photograph albums. Also, avoid pressure-sensitive tapes and damaging fasteners such as paper clips and rubber bands. Because adhesives can be problematic, photo­ g raphs that are sto red in p ap e r en v elo p es should be positioned with their emulsion away from the seam. Also, seams should be on the sides of the enclosure, not through the center. O nce materials have b een properly housed in w indow mats, folders, sleeves, or envelopes, they should be stored in cabinets or boxes of archival quality. Horizontal storage is prefer­ able for many photographic prints and for over­ sized photographs. It provides overall support to the images and avoids the possibility o f me­ chanical damage such as bending. Vertical stor­ age is often preferred for negative collections, but it can also be very effective for certain ph o ­ tographic print collections. Vertical storage is often more efficient and may make access to a collection easier. Glass plate negatives require vertical storage in order to prevent breakage. However, very large plates should be supported horizontally. W hen using vertical storage, pro­ tect materials by placing them in acid-free fold­ ers. These folders should then be stored in ei­ ther hanging files or docum ent storage boxes. Boxes should be housed on metal shelves or in metal cabinets. W here possible, materials o f similar size should be stored together. Mixing of sizes can cause abrasion or breakage. Regardless of the size of the objects, all enclosures w ithin a box should be the same size, should be larger than the materials stored in them, and should fit the box or drawer. Boxes and files should not be over crowded. ■ 5 64 /C&RL News