Quick guide on how to craft 100% elemental damage weapons with relatively high success rates.
You need to get yourself either a Shadow or Copper runic hammer (anything higher will result in you getting far too many junk mods and creating useless weapons).
Select Powerful Reforging, Grand Artifice and Inspired Artifice and select Exquisite/Of Quality as your prefix/suffix.
You'll get more junk mods with copper but a higher chance at getting the 100% elemental damage, you just need to weigh up which route is best for you.
One thing to note (not sure if this is a bug or not) but if you hit a durability x% on the weapon you reforge, eg. Scimitar, Durability +90%, 100% Poison Damage, 40% Damage Increase, and decide that you want to keep it so you PoF the weapon to 255/255 and start imbuing, as soon as you hit that first imbue the imbue intensity will SKYROCKET up into the thousands, as it counts the 255/255 durability as a property. Just warning people so you dont waste your PoF, and that if you want that 100% poison weapon to train a skill then imbue carefully if at all

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Sam