The study into degradation of 19th-century paper was undertaken from historical literature sources on the manufacture of paper. The change from handmade paper to machine-made paper and the increase of the production volume involved with the use of materials/machines, chemicals and methods had a definite influence on the product, often adversely. Important factors are the porosity of the paper, the amount of sizing and the presence and mobility of iron ions. The authors found that studying historical sources on paper-making leads to meaningful hypotheses for the study of paper quality. Where information is lacking, measurements on historical papers may help in filling the gaps. -- SCMRE