As we know using a higher grade fortification scroll will increase the success rate. There are special items(Vindictus) that can be found or bought from the cash shop that significantly increases the chance of a successful fortification.
When you fail a fortify you will find weapon or armor's durability is reduced to 0, fortification scroll is consumed and you need to repair your weapon/armor before you can fortify further which will have a very small chance of permanently reducing the item's maximum durability.
So a greater hammer of repairing (cash shop) can be used to bring back all the lost durability of an item in vindictus gold. Your equipment can has it's total durability reduced till 0/2 durability before requiring a hammer of repairing.
Maximum fortification limit is +9. Once your weapon becomes +5 it starts to glow and have a small lightning effect, +7 will glow even brighter and +9 will add a small sparkle effect. Armor does not glow when enchanted. Fortifying a weapon will add +3% increase to the ATK and MATK of the weapon per fortify and +3% to the item's defense value if it is an armor.
There are 2 types of fortify scroll one for weapons and another for armor. Each type has 3 grades of scrolls that increases success aptly named as C, B and A. C grade fortification scroll can only be obtained as quest reward and monster drops. B grade fortification scroll can only be obtained as an uncommon monster drop (lvl 31+ monsters). A grade fortification scroll can only be obtained from a BOSS drop.