What media did Irenaeus used to write his letters?

Question

Eusebius of Caesarea (AD 260/265 – 339/340) in his work Church History (Book V, Chapter 20 "The Writings of Irenaeus against the Schismatics at Rome") said:

Irenaeus wrote several letters against those who were disturbing the sound ordinance of the Church at Rome. One of them was to Blastus On Schism; another to Florinus

and then Eusebius cites the letter:

These things being told me [Irenaeus] by the mercy of God, I listened to them attentively, noting them down, not on paper, but in my heart.

The same passage in Greek (Source):

[5.20.7] ταῦτα καὶ τότε διὰ τὸ ἔλεος τοῦ θεοῦ τὸ ἐπ' ἐμοὶ γεγονὸς σπουδαίως ἤκουον, ὑπομνηματιζόμενος αὐτὰ οὐκ ἐν χάρτηι, ἀλλ' ἐν τῆι ἐμῆι καρδίαι·

• What media did Irenaeus use to write those letters?
• How was the media preserved for Eusebius to quote them two hundred years later?

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Irenaeus (130–202 AD) could not have written on paper which was invented much later? What media had Irenaeus used to write his letters? Where could the letters be stored for almost two hundreds year until Eusebius got them?

The obvious answer to some of the above questions would be to say that Irenaeus used/refered to papyrus. But taking in mind that:

• it was rather expensive and unreliable material since "papyrus was replaced in Europe by the cheaper, locally produced products parchment and vellum of significantly higher durability in moist climates"

• it appears that it was not widely used for taking notes since "until the middle of the 19th century, only some isolated documents written on papyrus were known, and museums simply showed them as curiosities"

I find this answer doubtful.

UPDATE

First I would like to thank everyone for answering my question. Nevertheless, let me once again emphasize that "Irenaeus refered to papyrus" is not the answer I'm looking for (see above).

The age of "ancient papyrus" can hardly be determined precisely today. Recent article in Nature Scientific Reports concludes:

As we can infer from the studies of the aged reference paper samples, the effect of artificial aging cannot be told apart from the effects of natural ageing by the methods used by us.

And since "until the middle of the 19th century, only some isolated documents written on papyrus were known" we can only be sure that papyrus can survive ~200 years in modern museums (between glasses, with air-conditioning, modern chemistry etc).

Answer 1

First, note that Eusebius doesn't tell us what material Irenæus used, but what material he himself didn't use. Today I could make the same poetic distinction, albeit a somewhat lamer version:

He sent me his reflections, and I uploaded them, not onto a USB stick, but into my mind.

This doesn't indicate that he sent me them by USB, but just uses the metaphor of digital sending that is our norm today (metaphorizing and extending his sending).

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However, I admit that's a technicality, and let's suppose — quite reasonably — that Eusebius' metaphorical use of "paper" is meant to directly mirror Irenæus' physical use of it.

Note that some dictionaries define χάρτης only as "paper" or "book", which should alert us to the fact that "paper" can be used as a category and not a specific material the way we use it today. The translator of your Eusebius passage has decided not to specify the material but to use the category term. "Paper" in this sense is only a shade or two more concrete than our "something to write on".

The two concrete realizations of said category for Irenæus' time are of course papyrus or parchment, and you can find support for χάρτης being used for either one, as in this dictionary or this translation:

... καὶ νύκτωρ ἐπιφαινομένη βιβλίον τί μοι πάντως ἢ χάρτην ὤρεγεν ...
... she always held out a book or a sheet of parchment ...

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So all that's left is to ask, since Irenæus — like many in the early church — sent letters on one or the other, which was it and how was it preserved till Eusebius' time?

Here's an article on the basic writing process used in Biblical times and presumably for the next few centuries till true paper began to creep in from the east. My own knowledge of the relative frequency of the materials is nil, so hopefully someone else can add that part.

However, to your question of longevity: there were ancient preservation methods, and in the right climate it could last much longer:

In a dry climate, like that of Egypt, papyrus is stable, formed as it is of highly rot-resistant cellulose; but storage in humid conditions can result in molds attacking and destroying the material ... In European conditions, papyrus seems to have lasted only a matter of decades; a 200-year-old papyrus was considered extraordinary.

Another common method of preservation (and transmission) was simply to copy the content out again. From its beginnings, the church always collected money and one use was to fund the preservation and distribution of important texts. We mustn't underestimate the importance and reverence the early church community had for its canon, including its growing canon under its leaders. As in any religion, those close to the founders or the core tradition quickly gained authority in the community, whether during their lifetime or shortly after their death — easily within the scope of papyrus' longevity.

The last theory is that Irenæus' letters were lost to time and Eusebius is lying that he had access to them, but there's no particular reason to suppose that.