Lead Ruling on Herculaneum Papyri

A recent Nature article has observed lead ruling on several Herculaneum papyri, including three different patterns:

1. top, bottom, and left column borders;

2. top, bottom, and both left and right column borders;

3. top, bottom, left, and right column borders AND horizontal line ruling on each line.

This has long been suspected based on literary references, but here we have it demonstrated in ancient papyri. Scribes apparently had lead discs and rulers that they used to rule the lines in preparation of the layout. Interestingly, these lines are intentionally laid out to produce columns slightly slanting to the right, an aesthetic phenomenon commonly known as Maas's law.

We have a similar situation in some of the Dead Sea Scrolls, where the lines are ruled with a light gray substance sometimes thought by editors to be "diluted ink." See, e.g., 11Q17:

https://www.deadseascrolls.org.il/explore-the-archive/image/B-365349

For someone with the time, interest, and technology, it would be interesting to check this and other scrolls noted in Tov's 2004 Scribal Practices book (section 4a) to see whether they are actually also ruled in lead.