I have a fountain pen friend in London with whom I have been corresponding with since this past fall. Her letters are a hoot, as she has a rapier wit and the ability to convey it into the written word.
She writes her letters on this amazingly thin smooth paper that I finally got around to asking her about. It is as close to the old airmail paper that I think can be found.
We found only one supplier (and believe me I scoured the web for a US source without success), Paper2Go, in the UK and they DO NOT ship internationally. In fact, they did not even respond to my inquiry about whether or not they would ship internationally.
Anyhow, the paper is called Biblio and here is how it is described on the website:
These super lightweight papers add an interesting dimension to many projects.
Biblio is 50gsm smooth paper, which despite being exceptionally thin, is also very strong and opaque. As its name suggests, it is the paper that Bibles are commonly made from.
So we arranged a trade. I found a pen that she was unable to obtain in the UK and she shipped me 300 sheets of this amazing paper. It retails for £8.95 per 100 page package. The paper is A4 size.
The paper works best with an extremely smooth nib. An italic or stub is even better, sharp nibs tend to cause bleed through. But this paper is not one on which I would write on both sides anyway, due to the thinness and translucency of the paper to begin with.
If you are in the UK you are lucky and can just order this paper. If you are in the US you need good friends in the UK willing to buy it and ship it to you. Oh, one warning, the shipping is NOT CHEAP.
Click on the photos to see them in their original size:
I really do not think that the photos above give a completely fair example of the true performance of this paper, so I used it to write a letter this evening. This is the back side of the pages. I wrote the letter with a Sheaffer Touchdown with a 14kt F nib. As you can see there is no bleed through. This paper is well worth the effort.