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  How do we prevent paper degradation?
 

Project aims

Why does paper degrade?
› How to prevent degradation
Paper stability estimation
What is chemiluminescence
CL and the cultural heritage

The conservation strategies are suited to the specific degradation chemistry of a particular type of paper.

Mass deacidification

Mass deacidification facility
at ZFB, Leipzig, Germany

CIDITY IN PAPER (originating in the sizing procedure during production) is counteracted by introduction of moderately alkaline CaCO3, MgCO3 or similar chemicals. By doing this, the acidity is neutralised, while usually some excess carbonate serves as alkali reserve to counteract the production of acids during future material degradation and possible absorption of acidic gasses from atmosphere. The procedure is called deacidification and is most often done by hand, although in big reaction chambers designed at several institutions worldwide, several hundred volumes can be treated at the same time (mass deacidification).

Hand deacidification

Hand deacidification by immersion of individual objects into an aqueous solution of magnesium bicarbonate.

Once the paper is moderately alkaline, oxidation by atmospheric oxygen (autoxidation) and alkaline degradation are the predominant degradation mechanisms. The rates of these processes depend on alkalinity of the sample and on the presence of catalysts, such as transition metals (iron, copper, etc.), often contained in inks and pigments. Some types of paper, including most paper produced prior to 1800 and modern permanent paper already contain alkali-earth carbonates and are therefore comparatively stable. In order to prevent oxidation, compounds called antioxidants are introduced. There are several types of antioxidants and they are classified according to the mode of action (preventive antioxidants, free radical scavengers, antioxidants synergists). With regard to alkaline degradation it is important to realise that cellulose is most stable in the pH interval between 6.5 and 8.5, deacidification chemicals introducing a more alkaline environment may be harmful.

 

 
Papylum. Anno MMII