Measuring the impact of parchment production on skin collagen stable isotope (δ13C and δ15N) values

Parchment is one of the most abundant resources in archives across the world, and is a unique time- sensitive material through which centuries of livestock economies, trade and craft can be explored. We examine the impact of structural and chemical modifications during production to δ 13 C and δ 15 N values in the skin, particularly the removal of cutaneous keratins and lipids and the conversion of amide functional groups into carboxyl groups through alkaline hydrolysis. Through the manufacture of fifty-one parchment skins (sheep, goat, calf and pig) using both historic and modern manufacturing techniques, we found production resulted in a small enrichment in 13 C (average +0.12‰) and 15 N (+0.26‰). Our results pave the way for the isotopic analysis of parchment in paleodietary and paleoenvironmental studies for the historic period, and establish the acceptable C:N ratios in deamidated collagenous tissues.