A 2.7. Opacity, transparency

Transparency is an important indicator of the condition and quality of the parchment. Transmitted light is used to visually assess the transparency.

Transparency is a feature of thin, i.e. ca 0.8 mm and thinner, parchment. There are many reasons for the transparency of parchments. Transparency can also vary on a single sheet of parchment. The transparency depends on the processing of the parchment. Different means of thinning the skin were used in different regions. If more of the underside of the skin’s dermis was sanded off, leaving part of the top layer of dermis with the finer collagen fibres, the end result was parchment with greater strength and transparency. This technology was more widespread in the regions of Southern Europe. If more of the top layer of the dermis was ground off, and the softer area of the subcutaneous side with a coarser fibrous structure remained, a soft velvety parchment with less transparency was produced.    This process was characteristic of Northern Europe. However, the transparency of parchment can result from chemical changes that occur when the parchment degrades. As a result of careless processing or various damage, a single parchment sheet may have both transparent and opaque areas.