Hello Jonathan,
I cannot say that I have printed on the reverse side of a photo paper, but I make postcard sized photos for my wife's store, that people can write on. After trying a number of papers (4x6 here in Canada) that Ilford Galerie Smooth Gloss and Ilford Galerie Smooth Pearl both produce nice looking cards and you can write on the back of the sheet with a regular pen, but some drying time is needed. I liked the Ilford papers better than anything else I used because the small sheets came as 290gsm. I had bought many boxes at once but now see that Ilford have rebranded and changed the paper slightly. It is now called Ilford Galerie Prestige and comes in at 310gsm. This paper should be the same as the older lighter paper, but as I have not tried it, I cannot say for certain. I still have a lot of the older paper left.
Cross Fountain Pen Ink - no smudging after a minute or so
Namiki Japanese Fountain Pen Ink - more aqueous, takes a very long time to dry
Sharpie Pen Ink - good after 30 seconds
Cross Roller Ball ink - good after 30 seconds
Cheap Ballpoint (BIRO equiv) - dry near immediate, no smudge, but poor writing presentation
The roller ball ink was the best all around answer in my tests. We just put a small card on the sale stand to advise people. I was surprised to find that the Cross Fountain pen ink was as good as it is, but it is rather thick.
To print on the back, you might try making a software template for a postcard and running the paper first through a low heat laser printer so long as the paper path doesn't bend the paper over which may damage the inkjet receiving layer. Some inexpensive black and white lasers offer a nearly straight paper path. I only have a colour laser here to test and it has a full 180 degree paper path and would jam up.
I have printed postcards on this paper using both the Canon 9500 Mark II and the 9000 Mark II. My wife says she likes the prints from the 9000 Mark II because the colours are punchier, a comment I have heard before given that the 9000 is dye and the 9500 is pigment. I don't use my Epson 4900 for prints that small, probably because it's so fast to print small prints on the Canon, just stack the paper in the rear feeder and let it rip.
I hope that this helps.
Ross
