WEI T’O® NONAQUEOUS MASS DEACIDIFICATION SYSTEM
Wei T’o® was founded in 1972 to make the nonaqueous deacidification solutions invented by Richard D. Smith at the Graduate Library School, University of Chicago, available for use in preserving archive and library collections. Today Wei T’o® Associates offer deacidification sprays and solutions; deacidification, freeze-drying, and non-chemical fumigation equipment; and preservation consulting services.
Our major achievement is the Wei T’o® Nonaqueous Book Deacidification System, the first production-proved mass deacidification system. It has the capability of beginning deacidification at one end of a general archive or library collection and proceeding to the other end with negligible pre-selection or damage. This mass deacidification process has been in operation at the National Library of Canada and the National Archives of Canada in Ottawa for 17 years. Well over 1,000,000 books have been protected against aging from acid attack, more than all of the other systems added together.
At the National Library, books are first vacuum dried for 36 hours and then deacidified in a 50 minute treatment cycle. The deacidification agent, an organic magnesium carbonate, and its solvents are impregnated into the books or documents under pressure. The solvents are removed by vacuum drying to deposit the deacidification agent throughout the books and paper fibers. The books are left in their processing baskets overnight to recover their moisture content and become ready for use.
The process has been applied to a comprehensive variety of materials to establish its effects on different papers, inks, and binding materials. The limitations from the new “Good News” HFC-134a formulation are: a few plastic-covered books and film covered paperbacks may be slightly defaced but no information is lost. During the past eleven months, only one (typewriter ribbon) ink feathered slightly and struck through on under ten pages of a 1920’s book; none of the other typescript pages were affected. Books containing typical book papers, coated and super calendered papers, tattered, yellowed and embrittled pages, purple mimeograph and modern “fast” print pamphlets, with all types of black, colored, and annotated inks are treated routinely. Leather-bound rare books are not treated because of lower temperature requirements for drying aged leather. Laboratory aging studies indicate the Library is extending a book’s life three to four times, depending on its condition and fiber content.
The Wei T’o® deacidification process normally does not change the appearance of a book. Without chemical tests, it is almost impossible to tell a volume that has been deacidified from one that has not been protected against acid attack. Archival records may be deacidified inside their boxes with a comparable high quality of treatment.
This Canadian Wei T’o® System was designed to be large enough for production scale economies but small enough that changes were affordable during its design and testing phase. It will easily deacidify 120,000 volumes per year when operated five days per week.
Larger and smaller units can be custom built and safely operated inside existing library buildings in city centers. Mass deacidification services will be made available from Wei T’o® when and where ever archivists and librarians desire.
Additional information is provided by “New Wei T’o® Products: an Unexpected Achievement” elsewhere in this web site. “Mass Deacidification from Wei T’o®,” an 18 minute VHS video tape, presents and explains the operation of a model design. A bibliography of independent articles evaluating the Wei T’o® will be added to this web site soon; publications by Dr. Smith are listed in Learn More about Our Founder.