I'm really interested in learning more about this bleaching method and its applications. M Carter (and you others who use iodine), if you don't mind a bit of a digression, would you be so kind as to educate me a bit? I use ferricyanide alone and as a rehalogenating bleach when printing (prints are still wet) but have always etched away small black spots when spotting prints. If there's a better way, I need to learn about it.
The cool thing about this (to me anyway), is you can use it on a dry print. With a very fine brush, you can do things like lighten specific blades of grass (I had a pinhole shot of an old railroad bridge with weedy foliage in the foreground making a cool framing pattern, and I was able to subtly "pop" that in a way that would have required specific enlarger masks). Since the print is dry, the bleach spreads very little.
You use a fine brush or a toothpick (or even a toothpick shaved down to a needle with a retoucher's loupe or headworn magnifier, this for really really fine work), and when the bleaching kicks in, you wipe it away with a q-tip or cotton ball with alcohol on it (I use 90+ isopropyl for the wiping). The emulsion dries in seconds and you can go again, so the possibilities to hit very fine detail are enormous.
For lith prints with black spots, I use it pretty strong with a toothpick shaved to just a splinter. The wood absorbs enough bleach to apply a very thin amount. For other uses, you thin with alcohol to get the desired strength. You can even do bleaching that sort of works with the grain pattern (esp. lith prints). Dilute bleach can be used for retouching, if there are things that will fade into the print to be less prominent, dilute bleach can let you really tweak things like that.
I have three half oz. cosmetic bottles, one with strong iodine (like a half gram of crystals dissolved in methanol) and one with 5% thiocarbamide. I mix equal part of thio, iodine, and alcohol in the third bottle as my working bleach, using an eyedropper - when the iodine and thio mix, the solution goes from red to clear. The alcohol will evaporate over time, so you have to watch that the solution doesn't get stronger over an hour or so. You have to re-fix really well - the spots can develop out in Selenium and other processes.
Also, I keep the bottle of iodine crystals and the small mixture bottles in a heavy-ish weight "tupperware" style container with the lid sealed - I've noticed the iodine off-gasses from the bottles and stains things nearby (mainly the sheet of paper with the formula I had tucked in with that stuff - it looks like a thousand-year-old browned document now).
I've found the bleach can eventually even bleach out selenium tones areas, but it's really something you want to do
before any toning steps.