I bought for next to nothing a fungus infested Reflex-Nikkor 1000mm/11, NKJ first edition (the one with a filter turret)
By applying the suggestions from Richard Haw (thanks Ric!), I proceeded to remove the fungus from the lens. Only the front element was badly infested (see photos before and after treatment).
I used an ammonia solution where I treated the front element (10 mm thick!) for about 5 minutes. there were no evident fungus tendrils on the other elements and/or the barrel, but I suspected the presence of spores, so I did an additional thing to what suggested by Ric: I used an ozone generator, the type that is used to sanitize hotel rooms and the like. Using a small plastic pipe, I saturated a closed environment (plastic box) with ozone, with my lens inside it (3 min treatment, leaving the ozone to act for the next two hours).
Mounted the front element, the lens is now free from the fogging that affected it.
Easy and quick, this work falls in the EASY category. Only a large lens spanner (110 mm span) is required.
Next modding on this lens: removing one of the B/W filters from the filter turret, and replacing it with a clear filter covered with a Baader solar filter. Then -maybe- extending the lens hood to a proper length, like I'm doing with the 400mm/3.5 ED lens, which had a very short 50mm long hood (more details on another article in this section).
Ciao from Massimo