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Thanks guys, I suppose it is obvious the more varieries documented in a denomination the more people are going to be interested in collecting them, and the more people collecting them the more varieties are identified, and so it grows. Thanks for the links David, I have read the thread on here bout the Portcullis varieties and was aware of the 2p varieties but had not found that thread, so thanks for that. I'm putting together a piece for my local coin club newsletter on decimal varieties, but maybe it will take another generation to really get into collecting them, as with a lot of things, what we currently use is mundane, what grandpa used is collectable. Ian..

Nice solvent/acid there. However, olive oil is not water soluble and will have to remove residual with detergent of some ilk - I use the dish detergents we have on this side of the pond. The residue if washed in any sort of water will continue to react with the surface of the coin, and copper alloy will start to go a bit pinkish. 0.500 silver seems to attract chloride oxidants, almost regardless of the alloy. This would include PVC, but also other chloride/chlorite oxidants. These in turn can be removed by the acid quotient of olive oil as well as the compounding agent by the solvent action of the oil. Likewise it is useful in other brass & copper bits as well, much as your reported experiments support. So olive oil has a virtual family of organic compounds in it that make it up, including both polar (water soluble and acid components) and non-polar (hydrocarbon chain components). Sorry to harp on this bit. My recommendation: continue to experiment with exposure times, etc. but that after each "treatment" to please remove the residual oil as stated. I always tamp dry with high nap white cotton toweling. PM me if you'd like...