That peculiar smell/odor when some old books are opened might at times be associated with mold and foxing. We come across books with foxing that may or may not have strong odor. At least one of the two books that we have received in our lab mainly for foxing treatment has a very strong odor. As soon as this book is opened, there is a heavy smell and the only main problem we find is of foxing (apart from general acidic yellowing due to ageing).
Cain and Miller have developed a classification of foxing types by shape, colour and UV fluorescence examination [S. Bertalan (ed.), Foxing, in Paper Conservation Catalog, 8th edn., The American Institute for Conservation of Historic and Artistic Works, Washington DC, 1992,12].
It is possible that the appearance of foxing to be caused by chemical reactions of iron traces from the paper (iron oxide and iron hydroxide) and organic acids produced by fungus. Hey and Beckwith proposed these dual mechanisms:
1. damp → mold acid → activation of iron → increased acid → mold death;
2. damp → activation of iron → increased acidity → local encouragement of mold → increased acidity → death of mold [ M. Hey, The Antiquarian Book, Monthly Review, 10(9) (1983) 341].
Question that remains is if the foxing needs to be treated for stains or fungus/mold or both or neither…