<>Vacuum freeze-drying, a method used to salvage water-damaged archival and library materials: a RAMP study with guidelines prepared by
John M. McCleary
General Information Programme and UNISIST
United Nations Educational, Scientific and Cultural Organization
Paris, April 1987
Recommended catalogue entry:
McCLEARY (John P.).- Vacuum freeze-drying, a method used to salvage water-damaged archival and library materials: a RAMP study with guidelines/prepared by John P. McCleary/for the/General Information Programme and UNISIST. - Paris: Unesco, 1987. - vii, 63 p; 30 cm. - (PGI-87/WS/7)
I - Title
II - Unesco. General Information Programme and UNISIST
14. What freeze-drying will not do 15. Cooperative approach to the use of freeze-dry chambers
15.1 General considerations
15.2 Regional cooperation
15.3 Cooperation with public institutions
15.4 Commercial cooperation
16. An open forum on freeze-drying
16.1 Questions and answers
16.1.1 In simple terms, what is the difference between freeze-drying and plain vacuum-drying?
16.1.2 Is freeze-drying expensive?
16.1.3 What about the cost of vacuum-drying?
16.1.4 Can wet (non-frozen) materials be freeze-dried, and conversely, can frozen materials be vacuum-dried?
16.1.5 Which is the better system, freeze-drying or vacuum-drying?
16.1.6 Shouldn't time be taken to sort or weed out wet materials prior to wrapping and crating for freezing?
16.1.7 Shouldn't wet materials be cleaned of soilage prior to freezing?
16.1.8 What is the best way to wrap wet materials for freezing?
16.1.9 At what temperature should water-damaged materials be frozen and stored?
16.1.10 Vet books and documents undoubtedly swell and expend with freezing. Doesn't that cause damage?
16.1.11 Do you deed a special chamber for-freeze-drying books and documents?
16.1.12 Bow do you know when the materials in a chamber are dry?
16.1.13 Is there a risk of overdrying and, as a consequence, run the risk of damage to the materials?
16.1.14 Can parchment and leather be freeze-dried?
16.1.15 In the freeze-drying process, heat is sometimes applied to the frozen materials. First of all, why is it done and doesn't the heat harm the materials?
16.1.16 Once the materials come out of the freeze-drying chamber can they go straight back to their shelves?
16.1.17 Would it not be less costly to replace water-damaged materials than freeze-dry?
16.1.18 It is generally knows that freeze-drying will not destroy mold spores, but what about insects?
16.1.19 How do you go about freezing insects?
16.1.20 Why weren't the infested books fumigated?
16.1.21 What should you do ii mold is widespread before the wet materials can be frozen?
16.1.22 Can mold-infected materials be fumigated in the same chamber where freeze-drying takes place?
16.1.23 It freeze-drying seems to destroy the visible growth caused by mold spores, why is it 80 necessary to sterilize and fog with a buffers? Why not put the dry materials in proper storage?
16.1.24 Some institutions hare photographic materials in their holdings. Can they be frozen and freeze-dried?
17. A final word: disaster preparedness planning
17.1 Why prepare for a disaster?
17.2 What a disaster preparedness plan contains
17.3 Prevention: central to disaster preparedness
<> Preface In order to assist in meeting the needs of Member States, particularly developing countries, in the specialized areas of Archives Administration and Records Management, the Division of the General Information Programme has developed a long-term Records and Archives Management Programme - RAMP.
The basic elements of RAMP reflect and contribute to the overall themes of the General Information Programme. RAMP thus includes projects, studies and other activities intended to:
- develop standards, rules, methods and other normative tools for the processing and transfer of specialized information and the creation of compatible information systems;
- enable developing countries to set up their own data bases and to have access to those now in existence throughout the world, so as to increase the exchange and flow of information through the application of modern technologies;
- promote the development of specialized regional information networks;
- contribute to the harmonious development of compatible international information services and systems;
- set up national information systems and improve the various components of these systems;
- formulate development policies and plans in this field;
- train information specialists and users and develop the national and regional potential for education and training in the information sciences, library science and archives administration.
This RAMP study covers the conservation of archival documents and the application of freeze-drying to the salvage of documents damaged by flood. As indicated by the author, the study summarizes a broad spectrum of data on freeze-drying and cites two methods in current use for drying water-damaged archival and library material, gives ideas on disaster preparedness planning and identifies recommended literature which is given in the list of references accompanying the study
Comments and suggestions regarding the study are welcomed and should be addressed to the Division of the General Information Programme, UNESCO, 7, Place de Fontenoy, 75700 Paris, France. Other studies prepared as part of the RAMP programme may also be obtained at the same address.
<> Foreword Freeze-drying is a familiar term thanks to the propaganda given certain consumer foods and beverages available on the market. These vary from dehydrated strawberries to brownish Crystals in a Jar that with hot water are converted to a cup of coffee. Some people may know that such products are made in a vacuum chamber, the same type as those used as simulators for training astronauts, or testing satellites and moon vehicles before launching them off into space. But, mention a vacuum chamber or simulator as an effective tool for drying a ton of documents soaked by a broker water main, or stacks of books soaked by the fire hoses used in fighting a blaze, and the number of those up-to-date diminishes.
Among archivists and librarians are many who remember "reading something about it" in professional periodicals, but retain a fleeting idea of what the process is, how it works, how it applies to them. Hence, the purpose of this study: to fill the information gap. To this end, the study summarizes a broad spectrum of data that includes, among other relevant facts, the behavior of paper when wet, its vulnerabilities in this condition, stabilization by freezing, vacuum chambers and how they dry, and selected case histories where such chambers were used successfully to salvage water-damaged documents and books.
The study cites two methods in current use for drying water-damaged archival and library materials: vacuum freeze-drying by sublimation and vacuum-drying by evaporation. The emphasis is on freeze-drying. Here, the wet materials must first be frozen. This produces a condition of total stabilization which, in turn, provides un unlimited span of time to think, plan, and decide what course of action to take. These advantages, however, do not indicate that vacuum-drying is automatically downgraded. As the study reveals, it is a very effective method of drying. But, since the materials normally are not prefrozen, certain exigencies could arise. For example, depending on conditions, wet materials might have to be placed in a chamber as quickly as possible to prevent attack by mold.
Many people-conservators, conservator-scientists, and manufactures-kindly furnished information on freeze-drying in response to letters written to them by the author. They warrant profuse thanks and gratitude for the time they took from their busy schedules to provide a reply.
<> 1. Introduction <> 1.1 Water: the ubiquitous hazard
The primary enemies of documents housed in archives and libraries have always been fire and-water, each an agent of a specific type of destruction. Although fires, with their spectacular display and awesome finality, are thought to be the predominate cause of destruction, in reviewing the literature on disasters in archives and libraries, the majority appears to be the result of water. In a fire-gutted building the destroyed holdings may have to be written off. On the other hand, although water can, under certain conditions, be Just as destructive the materials can be saved if appropriate action is taken.
Of the many recorded reports on disasters where water used to extinguish a fire did as much or more damage than the fire, there are two striking examples. The first was witnessed by Schmelzer (1), librarian of the Library of the Jewish Theological Seminary in New York City. In November 1966 a fire broke out in one of the top floors of the ten story building. AS a result some 70,000 books were practically burned to ashes. However, because of the open multitiered stack structure of the library, the water used to extinguish the fire poured down seven floors and damaged the remaining 150,000 volumes.
The second case, reported by Stender and Walker (2), involved one of the largest archives known: The National Personnel Records Office in South St. Louis, Missouri, which contains millions of individual records of former federal government employees, both military and civilian, in a six story building of solid concrete. In July 1963 a fire broke out on the sixth floor. Through a continuous flood of water, the firemen were successful in confining the fire to that level. But after the fire was extinguished, all Fix levels of the center had several inches of water on the floor. Water flowed freely through the building, especially through utility areaways and points where internal pipes ran through the floor. Broken water lines on the sixth floor added to the flood conditions. Some 10,000 cubic feet (280 cubic meters) of water-damaged records were removed for treatment from the lower flooded floors along with the several thousands of cubic feet or records from the sixth floor that suffered both fire and water-damage.
Although the water used to extinguish a fire can wreak destruction greater than the fire, this source of misplaced water is, fortunately, not too occasional thanks to the construction of fire-proof buildings and professional firefighters (3). On the other hand, there are many other sources of water that constitute a potential hazard to collections in archives and libraries. One source can be attributed to nature; tornados, hurricanes, floods, rainstorms, snow. The other to man: leaks in water supply or drainage pipes; breaks and/or leaks in steam pipes in the building; the breakdown of water heaters or air conditioning systems; clogged sinks, basins toilets; leakage of water deposits or tanks; leakage of roofs and windows; seepage in basements; clogged roof gutters and downpipes; broken water mains.
A classic example of the damage a broken water main can cause is found in the well-documented account of the Stanford University flood (4). OF November 8, 1978, an eight inch (25.4 centimeters) water main ruptured outside of one of the Stanford libraries - the Meyer Research Library - where new construction was underway. The rupture site was some 20 feet from the nearest wall. The flow of water was turned off about 20 minutes after the rupture took place. In the meantime, water entered the basement of the library where there were two levels of a metal-tiered construction and damaged some 50,000 research volumes.
<> 2. Water-soaked paper <> 2.1 Associated problems
<> 2.1.1 Absorption and swelling
Paper has a normal hydroscopic capacity for absorbing water. However, paper made before the middle of the nineteenth century has an even greater capacity for the absorption of water thanks to the greater amount of water-soluble sizing used in that early period. For example, books of this period will absorb up to an average of 80 percent of their original weight. Furthermore, paper of this period used for books or manuscripts is highly vulnerable to microbiological infection. However, such paper will survive total immersion in water for longer periods than paper made after the mid-nineteenth century. Books made after this time were treated with water-resisting sizes; they absorb an average of 60 percent of their weight. So, in estimating the original weight of a collection, if each book weighs about four pounds (1.81 kilograms) when dry and there are, for example, about 20,000 of each period, one must plan for the removal of 64,000 pounds (29,000 kilograms) of water from the earlier period and 48,000 pounds (21,773 kilograms) from the later (5).
As to swelling of books, the mayor part of damage takes place within the first eight hours after soaking.And since the text block and book covers swell more than the covering material, the tensions produced causes the spine to become concave and the fore-edge convex. The straining forces the case of the book to become partially or completely detached (5).
<> 2.1.2 Microbiological infection
Gallo (6) describes a number of schizomycetes (bacterial) actually low in number, and about 100 species of fungi which, under favorable conditions, attack and infest the organic matter in paper. Although the spores of the fungi and the schizomyceti are present in the raw materials used for the manufacturing of paper waiting for conditions favorable for development, the infection of documents is more attributable to the spores ever present in the air or dust. Spores Deed air to develop; a book or a bundle of manuscripts totally immersed in water are immune from attack. And since the spores of the fungi cause more frequent and greater damage than bacteria, this study will focus on the former.
The microbial spores of the fungal plant, of which the most common is called mold, need the following elements in order to reproduce: humidity, a relatively warm temperature, and a nutrient. The first, humidity, is present in abundance when water floods an archives or library. And a temperature higher than normal is present if the season is warm (the problem is less acute if it is cold), if ventilation is poor, if the air conditioning system breaks down, or if there is heat present generated by an extinguished fire. The third element, the nutrient, is essential because the fungal plant, which has no chlorophyll to convert carbon dioxide to carbohydrates for tissue growth, must get its carbohydrates directly from organic matter. Unfortunately, there is plenty of nutrition available in the cellulose of paper, the protein in parchment and leather, along with the nutrients in animal and starch adhesives used to size, glue and paste.
Kowalik (7) adds that microorganisms not only have cellulose at their disposition but also other substances such as lignin, hemicelluloses, pectins, waxes, tannin, and mineral constituents. Furthermore, paper may contain resinous fillers, dyestuffs, added during the productive cycles, and various impurities which may also form a part of the microbial diet.
In any case, if the temperature is in the 18° to 36°C (65° to 96.8 °F) range and the relative humidity above 65 percent, chances are that mold infection will appear on wetted books and documents in about 72 hours after flooding takes place This, however, is not a hard and fast rule. Waters (8) reports a case where mold developed rampantly on the water-soaked spines of rare books to a thickness of 1/4 to 1/2 inch (6 to 12.7 millimeters) some 52 hours from the onset of a disaster. As a matter of fact, during long-term storage fungi will grow, although slowly, at a relative humidity as low as 60 percent. And recently the National Library of Wales (9) experienced mold infection (no flood involved) on a number of items where the relative humidity was not only well below 70 precept, but in some cases as low as 50 percent.
The first visible evidence of mold infection is a white powdery mass that will appear on the surface of a document or a book. Sometimes you need a raking light to detect it. Even a slight trace is a warning that temperature and humidity are above the limits for safety. At this point, the fungal plant has grown hyphae (root-like organs) into the stratum of the nutrient in order to get food for its development. as the plant metabolizes the substances required for its growth, it secretes citric, oxalic, lactic, and other organic acids which damage the material on which the mold is feeding. At the same time, the plant secretes pigments of green, blue, brown, black, red, and yellow color which are deposited on the host. These stains are practically impossible to remove; they can obliterate the text of a manuscript or book.
When mold attacks paper other complex things happen: the strength supplied by the sizing in paper diminishes; when cellulose suffers the attack, the structure of the paper is damaged to the point that it will become soft or so fragile that it will actually break.
Gallo (6) points out that in some cases fungi can exercise a mechanical action on paper: their hyphae may filtrate between fibers of the paper without actually entering them, or the fruit bodies of the fungi, which are covered with bristles, infiltrate between one feat and another; in both cases the pages of a book or documents in a bundle are welded together.
<> 2.1.3 Adhesion of leaves
When a bundle of documents or a book has been soaked and permitted to dry under favorable conditions, it will begin to lose its water content from the outside surface. Capillary action permits the interior water to move outward and carry with it all varieties of water-soluble materials such as dyes, pigments, adhesives, and acids. In a book, the concentration of these materials, the acids and adhesives in particular, will cause the edges of the text block to become embrittled and edges stick together. Ii these text blocks are left in this condition after drying, serious degradation of the cellulose in the paper will be speeded up (8).
Books on coated paper present special problems. Coatings are usually applied to paper in order to obtain uniformity of surface, to enhance opacity, smoothness, and gloss. The basic components of coatings contain pigments such as China clay or a solubilized protein (10). Waters (8) notes that in the presence of water, starch-based coatings and some casein mixtures may revert from dry adhesive to gel and then back to the solid on drying. When these adhesive mixtures are in a fluid state, any pressure will cause the coatings to weld together and create a permanent bond during the drying cycle.
<> 2.1.4 Migration of inks and dyes
In case of wetted hand-written documents or bound volumes where inks have been used, the archivist and librarian face the problem of feathering or migration of those inks. In the two principal categories of inks, those made from carbon pose no problem since this organic material is not soluble: its binding medium (glue or gum), even when long decayed, leaves the carbon particles embedded in the paper fibers. However, there are inks that may look like carbon but are, in fact, quite soluble. In the second principal category are the so-called iron inks which are compounded from gallotannic acid in the presence of iron in a binding medium. Where carbon remains on the surface, iron inks soak into the paper so that the insoluble iron compounds formed when the ink matures are held as an integral part of the paper surface. In those cases where mature iron inks become a rusty brown or yellowish color it is not safe to assume that all inks of these tones are of iron and therefore insoluble. These same colors can appear with inks made of sepia or beechwood root which are impermanent (11)
Through all times inks have been made according to a multitude of recipes, and as a result vary in substance, appearance, and permanence. Some more modern inks are made "permanent" for fountain pens by using iron sulphate and tannic acid. However, the dyes used for toning will feather in water. Some inks used for writing have little more than a dilute aqueous solution of one or more synthetic dyestuffs. Other "permanent'' inks like those made of iron compounds will run or feather in water until they are matured or, said in another manner, properly oxidized. As for colored inks, most of them are soluble with or without aging.
While most holdings in archives and libraries are of non colored paper, the majority of the more modern material, even if it appears to be white, contains coloring matter added to improve appearance. For toning or coloring there are two mayor classes of colorants used: colored pigments and water soluble dyes. Of these the latter are the most used. The word ''soluble" means that a dye is soluble in water and colors the fibers from a solution in water. Such colors are impermanent and will run when wetted
<> 2.1.5 Time
The problems associated with water damage to archival and library materials - absorption and swelling, mold infection, blocking or adherence of leaves, migration of inks and dyes get worse with the passage of time; salvage becomes more difficult, costs may go up. Future repairs and restoration may become more complicated, more expensive and time consuming. In short, time is a problem if it is not available. However, there is a way to by an unlimited amount: you do it with a process called stabilization by freezing.