Resizing: A Brief Review of Restoration and Conservation Literature from the 17th to the 21st Century

From the first half of the seventeenth century until the beginning of the twentieth century resizing was common practice after each aqueous treatment to replace the loss of original sizing, but it is used much less frequently today. As already described in early sources, resizing in modern conservation practice still serves three main purposes: increasing mechanical stability, modifying the surface texture of abraded papers by decreasing their surface roughness and consolidating loosened fibres and preparing the paper substrate for inpainting. Today’s practice, however, differentiates more carefully between an improvement in mechanical stability and increased resistance to physical and chemical degradation processes. While previously almost exclusively protein glues were used for resizing, today gelatine and cellulose ethers are among the most commonly used sizing agents. The solution concentrations used for resizing have significantly decreased: gelatine is used in 0.5 % (w/v) to 1 % (w/v) solutions today, while historic literature recommends 1.6 % (w/v) to 3.5 % (w/v) protein glues. Concerning application techniques, mainly immersion, closely related to tub sizing used during paper manufacture and local or overall brush applications were used for historic sizing. Spraying, which was introduced at the beginning of the second half of the twentieth century, is recommended for resizing drawings to prevent friable media from being smudged.