Try mayonaisse... The sulfur from the eggs, the lemon juice and vinegar, all in one convenient package...
Also some tests wont work if the item being tested has too much of your test medium on it, some things actually keep the air off the blade and dont allow it to oxidize if it is going to.
I would sugest just wiping the substances on the blade versus submerging or glopping (technical term) it on..
Alan Folts