Equipment Needed For Decoding Tagged Vs. Untagged

The philatelic grade UV lamps are good enough for the modern GB. It's been my experience (at least for pre-2000 stamps) that the phosphor on the GB stamps can usually be easily observed even without the use of UV lamps. However, I've yet to find a suitable UV lamp for detecting the GB experimental phosphors. This was discussed in a few threads a couple of years ago. I can only find one of those threads (the other one had more information).

www.stampcommunity.org/topic...TOPIC_ID=5634

My home internet is down and I have limited internet access right now, so I won't have time to do a more extensive search for the other thread (there is a possibility it was discussed on another forum GASP). But the threads did not offer a conclusive solution for a UV lamp recommendation for the early GB experimental phosphors. I'm still open to an answer.

Also, if I remember correctly, doesn't the taggant wash off when soaking? or even in some material handling cases...so how accurate is this practice on say a pile of loose stamps that have a taggant variant??

It takes special effort to "wash off" the taggant. It normally will NOT come off with simple soaking in pure cold water. However, because it IS possible, as you noted, that is one of the reasons why you have to be wary of used "untagged" errors unless they are still "on cover". On modern US stamps that are on pre-phosphored paper or have the taggant embedded, it is almost impossible to wash off the taggant cleanly.

US tagging can transfer (and there are some Canadian tagged stamps that are real bad with that), so one must be careful not to put an untagged error into something that has held a tagged stamp.