George Papantoniou said:
If I wanted this effect, I guess that I could let some FP4 4x5 sheets drown in water for a while (in the dark !!!) then dry them and shoot them... water removes FP4's anti-halo layer effectively, doesn't it ?
Unfortunately, water also very effectively removes sensitizing dyes, so your FP4+ would probably be more like ISO 25 than 125 after you soak and dry it (in total darkness, of course). Actually, if you *want* to remove the antihalation, it would probably work better to use water with about a half teaspoon per quart of sodium carbonate; this will swell the gelatin and let the dye dissolve out more readily. A quick dip in common stop bath and then a wash (the Ilford wash is probably overkill for this process, but a couple changes of water to clear out the acetic acid would be good) before hanging to dry will return the gelatin to a "normalized" state.
I think it's probably easier to buy Lucky film, unless you need this effect in 4x5 -- Lucky is available in ISO 100 and 400, 35 mm and 120, but not in sheet form to the best of my knowledge.