Magazine article UNESCO Courier
Microwaves That Save Manuscripts
DEACIDIFICATION of manuscripts, books and archival documents is necessary today for two main reasons: the inferior quality of certain types of modern cellulose-based papers dating from the second half of the nineteenth century); and atmospheric pollution. Paper was formerly manufactured from textile fibres (linen, hemp or cotton) obtained from rags. Since 1850, cellulose fibres from broadleaf and coniferous trees have been used. The wood pulp is produced either by chemical or mechanical methods. Chemical pulp is of good quality, but paper made from mechanical pulp acidifies, especially when treated with sizing agents such as alum. This type of paper, used for newspapers or paperbacks, turns yellow, hardens, becomes brittle and finally disintegrates, a process that is aggravated by atmospheric pollution.
A method of deacidifying paper, discovered by an American and tested in Canada, has been adapted and improved at the French research centre for the preservation of illustrated documents in Paris, resulting in the design of the first assembly-line deacidifying plant in Europe. In 1988 a prototype was installed in the French Bibliotheque Nationale's preservation centre at Sable-sur-Sarthe.
The main advantages of this apparatus are that whole books can be treated and it is no longer necessary to take a book apart and soak the pages one by one in the treatment solution. Several books or documents can be treated at a time (as many as 250 a day).
The bound books are vacuum dried and heated, and the acid is then eliminated by soaking them in a basic alcohol solution. Subjected to a pressure of 4 bars, this solution penetrates all the pages.
In any attempt to preserve paper involving deacidification in an aqueous medium or strengthening by thermal sizing, or to restore flood-damaged paper, problems arise when it comes to the drying process. The paper is either dried in the open air on racks, or by means of traditional heating devices which are not really suitable (hot air blowers, heated plates or rollers, or infrared radiation). …