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6.1 Small outbreaks - localized high relative
humidity
6.2 Moderate outbreaks - Major and prolonged
periods of high humidity or minor flooding
6.3 Major outbreaks - Major flooding and
prolonged exposure
Literature
cited
The most effective treatment in all but the most extreme cases is modification of the environment and removal of the mold growth from the affected item. Most mold outbreaks, if dealt with promptly, can be controlled without recourse to biocides. Fumigants should be necessary only in the most extreme cases, for example, a prolonged delay in beginning treatment following a major disaster. Even in this worst case scenario, options such as freezing, if available, may eliminate the need for fumigants entirely.
Selection of the appropriate treatment should be based on an analysis of the problem and the nature of the material. Different approaches will be required for different media, and different levels of treatment will be necessary depending on the size of the outbreak.
A variety of treatments will be discussed, many of them incorporating some form of vacuuming. It may be that the vacuum is one of the most important tools in the prevention and treatment of mold growth in tropical climates. The use of vacuum cleaners or vacuum aspirators to remove mold growth from the surface of items, is, in the author's view, preferable to other treatments currently available. The vacuum removes all elements of the colony (spores, conidiophores, and mycelium) and packages them neatly for disposal. It is non-toxic, and if used properly, does no structural or chemical damage to the item being treated. Vacuums are readily available everywhere, and are economical to operate. Even when electricity is not available, they can be operated with battery packs. The major disadvantage of vacuuming is that it requires handling each book individually and treatment is therefore labor intensive.
The equipment needed for the removal of mold growth as recommended in this study is quite basic, and should be readily available in most areas. It includes:
Basic equipment and tools for the removal of mold growth.
- Portable vacuum cleaner with flexible hose and crevice tool for the removal of mold from book covers.
- Mini-vac for the removal of mold from paper surfaces.
- Powdered art gum eraser for cleaning the surface of paper too brittle to be vacuumed.
- Soft dusting brushes for the removal of art gum the surface of paper.
- Watercolor brushes with a fine point for removing mold from pastels and other fragile surfaces.
- Fine pointed surgical tweezers which may also be used for removing mold from the surface of delicate materials.
This section will describe treatment for small, moderate and major mold outbreaks, and provide suggestions for treatment of specific categories of materials, including books, unbound paper, photographic materials and the general area affected. Readers should augment this information with materials included in the recommended literature on procedures for dealing with major disasters.
6.1 Small outbreaks - localized high relative humidity
A small outbreak is here defined as the occurrence of mold on not more than a few hundred items. In a small outbreak, the mold affects only selected items or a specific area of the building, the materials are not actually wet, the mold growth having resulted from changes in the environment (usually an increase in the ambient relative humidity).
Treatment and modification of the environment should begin as soon as the mold is discovered. The delay of even a few days may turn a minor outbreak affecting only a few hundred items into a moderate outbreak affecting a few thousand.
6.1.1 Books
Small outbreaks of mold on bound materials are usually confined to the covers of books. They most often begin on the spine of the book, less frequently on the boards and around the turn-ins. Mold that occurs on the surface of book pages should be treated according to the recommendations for unbound materials below.
Mold growth should be removed from the covers of books by vacuuming, using small hand held or canister type vacuums with flexible hoses. The long slender attachment designed for cleaning crevices should be used, not the short round attachment with a brush. The brush attachment is not recommended as it will catch and hold the spores, conidiophores, and mycelium and prevent them from being drawn into the vacuum. The crevice tool will more effectively remove the growth by concentrating the pull of the vacuum on a relatively restricted surface area. A low power vacuum is best. One to one and a half horsepower is more than adequate. Large shop vacuums or wet/dry vacuums should not be used in the treatment of individual items.
The following procedures are recommended as a general guide:
- The affected books and the surrounding area should be examined to determine which materials are affected and why.
- Temperature and relative humidity readings should be taken in the immediate area. These readings should be compared to records for that area to pinpoint any changes. If records do not exist, readings should be taken in unaffected areas near by. As soon as the nature of the problems is determined corrective measures to modify the environment should begin.
- Affected books should be handled as little as possible during removal from the stacks. Touching the mold will transfer the spores to worker's hands and press the mycelium down onto the book surface. Books should be placed on a book truck, standing upright as they did on the shelves. They should not be stacked or carried by hand, as this will spread spores and compact the mold colonies.
- Treatment of the affected books should be carried out in a work area where there is adequate light for close examination. As each book is removed from the truck, the mold should be vacuumed from the surface. The entire book should be cleaned thoroughly. The mycelium may be present beyond the obviously affected area, but not visible.
- If the book has a hollow spine, the back of the book block should be examined to determine whether there is mold growth inside the spine. A flashlight may be used to see down into the middle portion of the spine. If there is evidence of mold growth on either the spine lining or the adhesive, alcohol or a mild fungicide such as Lysol (which contains orthophenyl phenol) can be used to swab the inside of the spine and the back of the book block. A cotton swab on a long stick (wooden or bamboo barbeque skewers are useful) should be used to apply the fungicide. The book should then be placed upright in an open positon and allowed to dry thoroughly before the volume is closed and returned to the stacks. It is not advisable to use either alcohol or Lysol on the outer cover of the book. They may cause staining, changes in the color of the cloth, or loss of gilding. For mold on the outside of volumes, vacuuming is preferable.
- Continue to monitor the conditions in the affected area with a psychrometer or recording hygrothermograph until it has been established that the problem has been corrected and conditions have returned to normal. Do not return treated materials to the stacks until the environment has been corrected.
6.1.2 Unbound materials (documents, maps, works of art on paper)
Mold may occur on unbound sheets of paper exposed to a high ambient relative humidity, or on materials in enclosed spaces (such as cabinets or glazed frames) where a microclimate has developed. Mold is less likely to occur on the pages of bound materials unless they are, or have been, wet.
Since single sheets of paper are not strong enough to withstand the pull of an average vacuum cleaner without damage, variations on the proceedures described above are required. Mini-vacuums designed for cleaning camera equipment, electronics and other delicate materials can be used to remove mold from the surface of documents without damage to the paper. If mini-vacs are not available, a vacuum aspirator can be improvised. (See Section VII. Equipment and Supplies).
The following procedures are recommended:
- Affected items should be removed to a work room for treatment. If files are involved, the file folders should be placed upright in open boxes during the move.
- The procedures for monitoring the environment described above should be followed.
- Framed items should be removed from their frames and the mats and backing materials discarded. Any information on the mats or backings should be copied and retained. The glass should be cleaned thoroughly with glass cleaner or a dilute solution of household ammonia and water. The frame should be thoroughly vacuumed before reframing.
- Works of art on paper, documents and maps should be cleaned with the mini-vac or a vacuum aspirator. Both the front and back of the items should be cleaned. After vacuuming with the mini-vac, the surface of the item should be cleaned with powdered art gum eraser. The art gum residue should be brushed from the surface of the item after cleaning and should be vacuumed up with the hand held or canister vacuum.
- If an item is very brittle the surface should not be vacuumed. Instead, reversing the procedure described above, powdered art gum eraser may be used to clean the surface. Cleaning should begin at the center of the item, and proceed toward the outer edges working in all four directions. The residue should be brushed off and vacuumed up. This will not remove the growth as thoroughly as vacuuming, but will pick up most of the spores and mycelium.
- Works of art with pastel, chalk or other friable pigments should not be vacuumed. In such cases the mold must be lifted from the surface of the item using a fine pointed, stiff bristled brush. A head band magnifier or magnifying glass should be used in order to insure the removal of the mold and to prevent the disturbance of the surface. The mold picked up by the brush should be removed from the bristles after each area has been cleaned using the vacuum or mini-vac. Very fine pointed surgical tweezers may also be used to lift mold from the surface of delicate materials.
- If only the edges of file cabinet materials are involved, they can be vacuumed using the crevice tool described above. If mold growth is extensive, folders should be discarded. Information on the folder should be copied and retained with the items. The discarded folders should be placed in plastic trash bags and removed from the area. Care must be taken to insure that the removal of the mold growth is complete. If there is any doubt regarding the extent of the mold growth, each sheet should be cleaned individually with the mini-vac as described below.
- If the mold has developed-in drawers, cabinets or other confined spaces the relative humidity must be lowered before items are returned to that space. The RH can be lowered by opening the drawers and cabinets and using fans to dry the interiors. Desiccants, placed in trays at the bottom of the cabinets may also be used in lowering the RH. If desiccants are used, they should be monitored and reconditioned when exhausted. If the problem seems likely to be a recurring one, the measures taken to correct the environment may have to be continued in order to maintain it. Desiccants are the most effective means of maintaining an acceptable RH in cabinets and drawers once it has been achieved.
6.1.3 Photographs, negatives and microfilm
The delicate emulsion surface of photographic materials makes the removal of mold more difficult, increasing the risk of damage to the image during the cleaning process. Prevention of mold is particularly important for such materials. In most cases, the development of mold on photographic materials is the result of a microclimate, and environmental conditions should be dealt with as above. In treating individual items, distinctions should be made between contemporary and historic materials. The commercial preparations available from photographic manufacturers for the removal or prevention of mold growth should not be used on historic materials.
- Monitoring and modification of the environment should begin at once.
- Storage boxes or envelopes with mold growth should be vacuumed thoroughly, or replaced if the growth is extensive.
- The non-emulsion side of the carrier, i.e., the paper, plastic or glass should be cleaned first. Paper supports on photographs should be vacuumed according to the instructions for works of art on paper. Contemporary plastic films, including microfilm may be cleaned with alcohol on a cotton swab or with a commercial film cleaner according to the manufacturers instructions. Glass plate negatives should be cleaned with alcohol or dilute ammonium hydroxide, taking care that the solution does not come in contact with the emulsion surface.
- Cleaning of the emulsion surface of negatives should be carried out on a light table. Mold should be lifted from the surface by lifting the mold from the surface using a fine pointed brush as described above in the section on pastel and chalk media. If there is any risk of damaging the emulsion further by cleaning, the mold should be left on the surface, and rendered dormant by using fans to dry the air and surface of the item.
- The emulsion side of contemporary photographs may be cleaned with commercial film cleaners. Historic photographs should be cleaned according to the instructions for works of art on paper. Never use water based solutions on the emulsion of damaged photographs. If the fungus has softened the emulsion, water will remove it from the carrier.
6.1.4 General area
In a relatively minor outbreak, improved air circulation is usually enough to bring down the relative humidity and lower the temperature in the immediate area. This may be accomplished by the use of fans alone, or by a combination of fans and dehumidifiers. Recurring problems may require the rearrangement of the area in order to improve air flow. The exact measures taken to correct a microclimate problem depend on the analysis of the situation at the time of the outbreak.
6.2 Moderate outbreaks - Major and prolonged periods of high humidity or minor flooding
A moderate outbreak is here defined as one involving a few hundred wet items or several thousand dry but moldy items located throughout the building. Two different courses of action are recommended depending on which of these conditions prevail.
Dry Moldy Items
For the treatment of mold resulting from prolonged periods of high humidity and affecting significant portions of the library collection, lowering the temperature and relative humidity through improved air circulation is the most viable option. Books should be vacuumed in the stacks if the number involved is too large to consider moving them to a treatment location. Cabinets and drawers should be opened and the contents vacuumed. They should remain open until the RH has reached an acceptable level and the situation is under control. Conditions should be monitored in all affected areas of the library. Any items that are felt to merit individual attention should be handled as described above in the section on minor outbreaks.
Wet Items
Detailed procedures for the salvage of large numbers of wet items has been covered in a number of publications. Two that are especially recommended are Procedures for Salvage of Water-Damaged Materials1 and An Ounce of Prevention2. These recommendations should be followed for the handling and treatment of wet materials. The recommendations below will focus on the prevention of mold growth during the treatment and drying of items that are wet as a result of localized flooding.
Localized flooding may occur as a result of burst pipes, leaks in ceilings, walls or windows, or from backed up drains or flooding in the lower areas of the building. If the flooding involves water from rivers or any form of backup from drains, precautions must be taken to protect workers from possible infection and disease.
6.2.1 Books
The recommendations below are intended as a general guide.
- Removal of wet items from the flooded area should be the first priority and should take place as soon as possible. Once the books have been removed, standing water should be removed. If left, it will contribute to continued high relative humidity throughout the area and may result in mold growth on items not directly affected by the flood. Water may be removed using pumps, wet/dry vacuum cleaners, or mops and buckets. Fans should be set up in order to lower the relative humidity and insure adequate air circulation.
- Wet items should be removed to a large dry area where fans can be kept in operation 24 hours a day to speed the drying and reduce the likelyhood of mold growth.
- Items should be dried on tables. Drying wet books on the floor should be avoided since circulation will be worst at floor level. If the drying process takes several days, materials on the floor will be more vulnerable to insect attack, and the handling of materials and movement around the room will be more difficult.
- Items should be constantly attended during the drying process. Pages should be turned and inter-leaving materials replaced frequently in order to insure relatively uniform drying. Interleaving papers should hung up to dry if they are to be reused. If they are to be discarded, they should be placed in plastic bags and removed from the area.
- As items dry they should be removed from the treatment room. Each item should be carefully inspected to be sure that it is completely dry before it is transfered to a storage area.
- If mold has developed it should be vacuumed off the items only after they are reasonably dry. No attempt should be made to vacuum very wet materials.
- If there are too many items: for a limited staff to handle, or if there are delays in beginning the drying process for some items, freezing may be necessary.
6.2.2 Unbound materials
- Wet items should be removed to the drying areas as soon as possible. Unbound sheets should be treated in a separate area of the room from bound materials. This will allow better use of space and faster drying.
- Matting materials should be removed and discarded if this is possible without damaging the item.3 Relevant information can be copied and retained with the item. If the item is mounted overall to board, no attempt should be made to remove it from the backing unless it is obvious that the adhesive is water soluble, and the item is already partially detached. If this is the case, the backing should be removed from the item a layer at a time. Do not attempt to lift the item from the backing. If items must be dried on backing boards, they should receive special attention during the drying process, since they will dry more slowly, and the adhesive may increase the possibility of mold growth.
- Individual sheets should be spread on tables to dry and turned frequently as soon as they are dry enough to be safely handled. If space is a problem, trays can be constructed from fiberglass screening and wooden frames, and stacked, provided that there is adequate space between them to allow air circulation.
- Rolled items should be carefully unrolled after they reach the drying area. Multiple items rolled together should be carefully separated for drying.
- Care should be taken in positioning fans. They should provide good circulation but not blow directly onto drying items. Partially dry papers can be lifted and torn by the draft from an improperly positioned fan. Air movement should be constant above and below the items, but not directly on them.
- Documents in file folders may be dried upright in the folders if only the upper edges are wet. If the entire folder or the bottom fold is wet, they must be opened and the contents spread out to dry.
- Materials should be removed from the drying room as soon as they are completely dry. If there is residual mud or evidence of mold growth they should be cleaned with the mini-vac and powdered art gum as described above.
For unbound paper items affected by flooding, freezing is usually not necessary. Since they will dry more rapidly, unbound paper should be attended to immediately, and materials which will require several days or weeks to dry should be chosen for freezing. These frozen items can then be dried in smaller increments as staff and space are available.
6.2.3 Photographs, negatives and microfilm
The gelatine emulsion on photographic materials is particularly vulnerable to water. The emulsion on black and white prints and negatives can tolerate approximately 3 days of immersion before the emulsion begins to separate from the support. Color prints and negatives begin to separate in only 48 hours.4 Like unbound paper materials, these items should receive priority treatment, particulary with regard to removal from flooded areas.
- Wet photographic materials should be removed from storage boxes or envelopes as soon as possible. The storage materials should be dried separately or discarded after relevant information has been copied.
- Mud or debris on photographic materials should be removed by rinsing with clean water before drying. No attempt should be made to wipe or brush residue from the emulsion of wet photographic materials.
- Microfilms should be unwound from their spools and clipped by their leaders to a line to dry. Flexible film negatives may be handled in the same way.
- Photographs and glass plate negatives should be air dried lying flat with the emulsion side up. They should not be placed face down or turned over until the emulsion side is completely dry.
6.2.4 General area
In most cases of localized flooding, the removal of standing water and the use of fans is sufficient to return the area to a functional condition. Conditions should be carefully monitored to insure that the relative humidity has returned to a safe level before items are returned. Materials should be checked frequently in the weeks after their return to the flooded area to detect any mold which may occur on items not completely dry.
Shelving and cabinets may be wiped down with alcohol or Lysol if there is evidence of mold growth on their surfaces. Sterilization of the area should be required only if the water is suspected of having been contaminated by sewage. Sterilization should be carried out by a qualified commercial fumigator, and staff and users should not return to the area until it has been thoroughly aired.
6.3 Major outbreaks - Major flooding and prolonged exposure
Major outbreaks of mold are generally associated, even in the tropics, with some form of natural disaster. Often the building is damaged, and support services such as power and water are unavailable. This can result in delays of days or sometimes weeks before salvage operations can begin. A well formulated plan for dealing with major damage to buildings and collections provides the best possible chance for salvage. Contacts with individuals and corporations which can provide needed materials and services must be made before the event occurs, or there will be virtually no chance of securing the necessary supplies. Contact numbers or addresses should include night and weekend numbers, since emergencies rarely occur during standard office hours. There is no substitute for a well formulated disaster plan.
6.3.1 Priorities and planning
Decisions as to which portions of the collection are to receive priority in salvage operations must be made in advance. Materials which can be replaced should be sacrificed and attention given to those which are irreplaceable. Priority is usually given to unpublished manuscript materials, items of particular monetary or historic value, and materials of local or regional significance. Recent periodicals, items held by a number of other institutions and collections of peripheral importance to the function of the institution may be considered replaceable or expendable. Experience has shown that these decisions cannot be made at the time of the disaster when shock and despair tend to overwhelm staff and administrators. A disaster plan which details the priority accorded to specific parts of the collection can ensure the salvage of the most important items in even the worst circumstances.
The plan should include:
- Those portions of the collection that are to receive priority for salvage and treatment and the order in which they are to be removed.
- What form salvage will take for each, i.e., air drying; freezing or freeze drying.
- Who will be responsible for overseeing the salvage of each specific portion of the collection.
All staff members should receive enough training to supervise volunteers in salvage operations and lines of command and communication should be clearly drawn. Whenever possible, equipment and supplies required should be maintained by the library, including one or more generators, vacuums, fans, plastic milk crates and trays for the removal of wet materials, and a stock of heavy plastic, fiberglass screening and absorbent paper such as toweling or unprinted newspaper stock.
Sources of additional materials and facilities should be part of the disaster plan, and should be available to a number of senior staff members. Copies of the plan should be kept in locations outside the institution.
Whenever possible, basic salvage procedures including air drying and preliminary treatment should be conducted on site. The difficulties of moving masses of wet materials increases the risk of physical damage and reduces the number of personnel available on site to deal with any unanticipated problems. Only if the building is so extensively damaged that there is no covered, relatively dry space available should an alternate location be utilized. It is useful to have a back-up plan that incorporates access to an alternate site, but it should be used only if absolutely necessary.
As soon as there is access to the building, items should be removed in order of priority. Items removed to the air drying area or to freezers should be processed according to the literature for the salvage of materials. The recommendations which follow will focus on measures which may help to prevent mold growth on items awaiting removal and treatment.
6.3.2 Prevention of mold growth on site
- Dry materials remaining in the area above the flood line should be removed if possible. They should be packed loosely in plastic milk crates and stacked in a dry, adequately ventilated area. They should not be placed in closed containers, since they will undoubtedly have absorbed moisture from the air and may become moldy if they are left in sealed containers.
- Standing water should be removed from all areas of the building as soon as possible.
- Fans should be set up as soon as the area is dry enough to allow the safe operation of electrical equipment, and should remain in operation continuously during the salvage operation. If dehumidifiers are available, they should be used in conjuction with the fans.
- If dry materials must remain in the stack areas, as soon as fans are installed, they should be separated on the shelves in order to increase circulation and speed the drying process.
- Carpets and draperies, which retain water and contribute to maintaining a high relative humidity in the area, should be removed.
- If the building is designed to take advantage of natural ventilation, windows should be opened as soon as possible to increase air circulation throughout the building.
- The building and materials should be frequently inspected to detect any signs of mold growth as soon as possible. If mold is discovered, every effort should be made to increase the air circulation in that area, and to lower the temperature and relative humidity.
Fogging of the area with a fumigant should be undertaken only as a last resort. There is no guarantee that fogging will prevent mold growth in the collection and relying on fogging alone may give a false sense of security. It may also prove hazardous to those who handle the material later in the salvage operation.
6.3.3 Freezing
In major disasters, air drying may not be possible for all of the affected materials due to time, space, and staff limitations. Freezing provides the best protection for wet materials which cannot be dried within a reasonable time. Items can remain frozen for months if necessary, while decisions are made regarding drying and treatment. If individually wrapped, they can be thawed and air dried in whatever quantity the staff and facilities can accomodate. Refrigerated containers of the type used by overseas shippers can be brought to the site and maintained with external generators for as long as necessary. The use of commercial freezing facilities in the area may also be possible, however health regulations may not allow the use of a space which is ordinarily used for the storage of food products.
6.3.4 Drying
There are, at present, only three viable methods for drying large quantities of wet materials. Air drying, vacuum freeze drying and vacuum drying are the only proven methods. Each has advantages and disadvantages, and usually a combination of methods is necessary to deal effectively with the number of items involved in a major disaster. Experiments with microwaves and other exotic drying methods have proven less than satisfactory, often causing additional damage to tile materials.
Air drying, has been proven effective, given adequate space, environmental conditions and personnel, but is relatively slow and very labor intensive. Wet materials must be continually monitored and attended to insure that the items dry completely and in the shortest possible time. Ambient relative humidity must be lower than that of the materials, and air circulation must be good for air drying to be effective. When air drying is possible, it is recommended for first priority items. Air drying is usually not possible for all items in a major disaster, and the majority may have to be frozen to await drying at some future time.
Vacuum freeze drying is costly and requires specialized equipment. However, it has the advantage of removing water from pre-frozen items without thawing them, reducing distortions and the chance of mold growth. The water is sublimated directly from the solid to the gaseous state and is drawn off by the vacuum. It is the most effective method of drying large quantities of,et materials. Libraries and archives preparing disaster plans should check for the availability of such facilities in the area, and if possible make arrangements for their use in emergency situations. Freeze drying facilities arc usually associated with food processing plants, and special permission from Health departments may be required for their use.
Vacuum drying removes water in its liquid state and previously frozen materials are partially thawed during the vacuum drying process. Warm, dry air is pumped into the chamber and water is drawn out by the vacuum. This process is considerably slower than vacuum freeze drying, and there is some risk of mold growth and further damage to water soluble materials. Vacuum drying also results in considerably more distortion of materials than vacuum freeze drying.
1. Peter Water. Procedures for the Salvage of Water-Damaged Library Materials. 2nd ed. Washington, Library of Congess, 1979.
2. John P. Barton and Johanna G. Wellheiser, eds. An Ounce of Prevention. Ontario, Toronto Area Archivists Group Education Foundation, 1985.
3. Marilyn Kemp Weidner. Instructions on How to Unframe Wet Prints. Cooperstown, N.Y., New York State Historical Association Library, 1973.
4. Barton and Wellheiser, p. 69