For centuries blotting sand has been used for drying ink on manuscripts, but very little is known about the nature of such sands. In this study, 165 blotting sand samples used from the 14th – 19th century in SW-Germany and northern Switzerland are analysed by petrographic methods. The sands and sand components are classified into seven categories (plus several sub-categories) as (1) Quartz-rich sands; (2) Heavy mineral concentrates; (3) Crushed black sands; (4) Mica sands; (5) Other crushed minerals and rocks; (6) Artificial components; (7) Biogenic components.
The dominating quartz-rich sands can be subdivided by grain shapes, and can occasionally be related to regional resources, as the use of some sand types is restricted to specific areas. For example, heavy mineral concentrates are strongly associated to the Rhine River where they emerged as a by-product of gold washing. Similarly, blue-stained quartz sand, coloured by synthetic Fe-Al-spinel (which appears in the 19th century), is restricted to places in Switzerland, suggesting its invention in this area.
The temporal variations in the preference of sand types have been investigated at several places. In Basel, Switzerland, a clear stratigraphy in preferred sand types can be demonstrated. To uncover such temporal patterns, the use of extensive sample series over several centuries was necessary.
One unexpected finding from this inquiry is a region in SW-Germany where artificially prepared black sands, including crushed Fe-Ti-ore and crushed staurolite, remained the preferred blotting sand type for more than a century. Blotting sand found in manuscript archives may contain otherwise lost information, which can be uncovered by the tools of mineralogy and by the cooperation of geological and historical sciences.