Outdated Ilford XP1

I've been using XP films since they were introduced and I found an undeveloped roll of XP1 in my studio that was exposed in 1990! When I had it processed yesterday the latent images had faded, but I got some prints. One group of images had reversed, that is printed as a negative image. Does anyone have any experience with what happens to chromgenic films as they age and if the revesal is "normal" chemical changes in the film.

Just curious.

I havent a clue, but this sounds like a very interesting side effect. I'd suggest it's something to do with the fading of the latent image coupled with the build up of fog. The latent image somehow masks the negative so that the fog "fills in" the unexposed areas, while the original latent image fades away, so you're left with a positive image. The flaw in that logic is that I'm not sure why the original exposure would fade away while fog would be retained. XP1 was cutting edge technology for it's day, so I doubt they could have known the sort of long term storage problems it could have had, maybe this was a product feature we never knew about

I'd be interested to hear from someone who actually has some idea what they were talking about, very interesting stuff.

Not sure, could be a variation on the reversal paper phenomenon where its pre-exposed, so that when its used in anger it goes over the curve and does reversal without all the intermediate steps.

XP1 was, as above cutting edge, but a bit temperamental at times. XP2 then XP2 Super cured a lot of the wackyness

I've heard of it happening before. It's like solarization.

I like Feath's idea and I've thought of solorization also. Thanks! I've been trying to email Ilford at http://www.harmantechnology.com/DotNetNuke/Contactus/tabid/62/Default.aspx but their server isn't responding.