Refine can be accessed by going to Menu or via player shops.
Stones that can be used for refining (only one can be used at a time):
Polinium - Quests, Pandora Boxes, Hourly Attendance box, etc.
Pure Polinium - Dapara (Master Point Merchant in Morroc)
Lucky Powder - Ranking Rewards (6-10), Daily Attendance, Events
Blessing Powder - Phantom Pyramid minigame, Events
The upper limit of refinement is currently +20. Refining can break at any level without infinium, except from +0 to +1. Stone for protecting is called Infinium. Before +10, any failures using infinium can reset to +0 (I think) will reduce by 1 level. After +10, any failures while using infinium can result in item resetting to +10. Nobody knows the real chances, but they are incredibly low most of the time and getting from +0 to +10 seems to be harder than getting from +10 to +20.
Players who achieved refining ranking can receive a back accessory that improves refining rates by a certain percentage. Other players can access this benefit by going to ranking player's shops. Gold ranking is better than Silver ranking in terms of the bonus. These Gold and Silver bonuses add a small chance to let you skip levels ie. using a Blessing Powder which normally does +1 more can have a chance to go +2.
Weapons can glow starting from +6. Armors don't glow.
I think that's all, but I could've missed some.
Edited by Arbalist, 21 November 2014 - 02:36 PM.