Following wetting, five drying protocols were tested in five different locations.3′
Air Drying with Intermittent Pressing
In a low relative humidity environment (30% RH) at the University of Utah (Salt Lake City, Utah, USA), wet books were stood on end on counter-high tables and fanned open to stimulate evaporation. None of the books were printed on coated stock paper so interleaving with silicon
release paper (or wax paper) was unnecessary. Supports to prevent books from falling over included plastic VeloBind4 combs inserted at the head of the text to act as a cross brace, as well as five-pound weights placed as necessary at the base of the boards. Six large electric fans were positioned around the table and turned on the maximum setting to circulate air thoroughly throughout the drying process, accelerating evaporation and discouraging microbial growth. As the still-wet books approached dryness (after approximately three days) they were pressed for
approximately 12 hours overnight between boards in a bookbinder’s standing press, and returned to the tables each morning for further fanning and air drying until all were thoroughly dry (taking five to seven days). Dried books were pressed between boards for an additional seven days
Vacuum Freeze Drying
At BELFOR USA (Fort Worth, Texas, USA) frozen books were placed on rolling wire racks inside a commercial vacuum freeze drying chamber. The books were firmly packed together on the racks, spine down, to help maintain their shape during drying. Vapor pressure within the chamber was reduced below the triple point of water (4.57 torr/0.6092833 kilopascals). A slight amount of heat (40.5 C/105°F),5 was introduced intermittently to the chamber to stimulate sublimation (direct conversion from solid to vapor). Ice from the frozen books sublimed and was
captured as ice on the unit’s evaporator coils outside the chamber. The chamber contents were checked daily after the fourth day and thoroughly dry books removed until all books were finished (approximately seven days). Although the vendor provides more expensive services in which books are freeze dried while physically compressed to yield flatter text blocks, this option was not part of this study to reflect financial constraints typical of most post-disaster recoveries.
In a commercial wood drying kiln outside Prague (Czech Republic), staff of the National Library of the Czech Republic placed wet books on elevated wire racks, and interleaved each book with sheets of absorbent paper (printed newsprint) every 10-15 pages. In addition to facilitating egress of water from the text block through wicking, these sheets were replaced daily to provide bulk removal of water. Books where then stacked vertically between pairs of unglazed ceramic tiles, and sheets of Holytex6 were placed between the unglazed tile surface and the book cover to
promote diffusion of moisture while preventing wet bindings from sticking to the tiles due to adhesive migration or thermoplastic adhesion. Each stack of books was weighted on top (3.2 kg/7.0 lb) to produce constant pressure that reduced text block distortion during drying.
Air was circulated within the closed kiln and the temperature raised to 60 C/140°F with the relative humidity set at 70%. After two days the relative humidity was reduced to 40%-50% while the temperature remained constant. Complete drying time took between seven and twenty
days depending on the size and physical characteristics of each text block and cover. Books with plasticized covers took much longer to dry as moisture was eliminated only through the edges of the text. Interleaving was replaced daily during routine inspection for dampness. When the
drying cycle was completed, the kiln was slowly returned to ambient conditions to allow books to equilibrate while still under mechanical restraint.
At the British Library (London, United Kingdom) wet books were interleaved with sheets of printed newsprint every 10-15 pages. If the wet binding felt slippery it was wrapped with Bondina7 to prevent the covering material from adhering to the polyester vacuum pouch (Archipress8). Placing the book inside the pouch, the edge was sealed with an Archipress Vacuum Packing Machine and a vacuum pulled. After several days the pouch was opened and the interleaving exchanged for dry blotting paper to remove bulk water, and a new pouch used to re-seal the book. Drying took up to twenty exchanges of bag and blotter over sixty days.
Vacme Press with Zorbix
At Artifex Equipment, Inc. (Penngrove, California, USA) wet books were interleaved with sheets of Zorbix9 every 10-15 pages. The covers were wrapped with Holytex to prevent binding materials from adhering to the inside of a proprietary, re-sealable vinyl bag integrated with a vacuum hose fitting (Artifex). The vinyl bag’s re-sealable opening was rendered airtight with a Teflon folder while it was evacuated with a vacuum pump (Artifex). Saturated Zorbix interleaving was replaced at 48 hour intervals. Drying required approximately six exchanges of Zorbix over fourteen days.