I recently came across this explanation by prof. Larry Hurtado of how ancient papyri are dated. I liked to share it with the readers of my blog.
You may read the full report with comments at: https://larryhurtado.wordpress.com/2016/06/24/dating-ancient-papyri/
Prof. Hurtado says:
“Further to my recent posts about recent proposals for the dating of certain NT papyri, let me briefly clarify the process of dating papyri, which might well seem a mystery to those not familiar with it.
There are two main types of papyri: “documentary” (letters, official documents such as land-transfers, marriage contracts, shipping bills, etc.) and “literary” (treatises, poetry, history, fiction, etc.). Documentary texts are often/typically dated by the writer, which makes dating the manuscript fairly straightforward. But literary texts are hardly ever dated. So in their case the only way forward is by estimating the approximate time-frame of the handwriting (often referred to as the “hand” of the manuscript).
Dating ancient Greek handwriting, for example, requires making comparisons with other dated manuscripts, and over the past several decades especially (as more and more papyri has come into view) palaeographers have tried to develop a broad sense of developments in Greek handwriting across several centuries (from the Ptolemaic period, from which our earliest papyri comes, to “late antiquity” or the Byzantine period). So, when examining some undated papyrus, palaeographers try to place its hand in that broad time frame, looking at the basic “style” of the hand.
They will, therefore, look for “comparators,” i.e., other dated papyri with a “hand” similar to the papyrus under investigation. It is especially important to look for comparators that are themselves securely dated, i.e., documentary texts. But, on the other hand, documentary texts are often written in a “documentary hand,” which is much like the difference between modern cursive writing and writing out individual letters. So, quite often, one must rely heavily on other literary “hands” in manuscripts that have themselves been dated by palaeographical comparison.
There are books containing photos of many papyri of various dates that one can consult to help in this. But the expert palaeographers will have looked at perhaps a few hundred papyri, developing a close sense of an inventory of “hands” that enables them to make judgements. This kind of expertise requires a commitment to this task, and the admiration and gratitude of the rest of us.
Sometimes, a literary text is written on the reverse (outer) side of a scroll, a re-use of a scroll. And if the original use of the scroll was for a dated documentary text, then that means that the re-use must have happened at some point subsequent to the original documentary text, at least giving an “upper” date limit.
But, as with all such judgement-activities, experts can disagree, often by several decades, even a century or so, and sometimes even more. In part, this is because different palaeographers take somewhat different approaches, some focusing more on the overall appearance of the “hand” and others focusing more on particularities of individual letters, for example. Also (and this is actually encouraging), sometimes a given expert can change his/her mind, revising an earlier judgement in the light of further reflection on the data.
It’s not, however, simply all subjectivism. And, contrary to one reported statement by a scholar not himself a palaeographer, it’s not all “bullshit.” Typically, people today will call for carbon-14 testing. But, as is evident from recent examples, carbon-14 testing can’t really do more than offer a certain probability for a timeframe of approximately a century or so: about the same timeframe that palaeographers can offer.
Further, as I noted in a posting a couple of years ago arising from a conference on papyri dating that I took part in, the results of carbon-14 testing of several papyri yielded date-estimates pretty much in agreement with the dating proposed by palaeographers. These tests, thus, suggest (1) that carbon-14 dating is no more precise than palaeographical dating, and (2) that palaeographical dating by really competent experts is broadly reliable, independently confirmed in these carbon-14 tests.
May this be as great a blessing to all my readers as it had been to me.