Level 4 Crafting Skills

You'll note that your crafting skills get stuck at level 3. And you won't be able to level them up to 4.

When you hit level 50 you'll get the crafting quest. This will allow you to get your crafting levels up to 4 and level it normally up to level 5. I have not experienced the level 6 crafting quest yet so I can't post it here.

You can actually prepare for the quest beforehand especially if you do craft regularly.

Here are the requirements:

Ironsmith Quest

NPC: Ironsmith - Dragon City North

Required Items:
1. ** Saw Tooth Dual Blades
2. ** Purple Vulture Bow
3. ** Warding Talisman Flag
4. 10 pcs. Tempered Steel


Tailor Quest

NPC: Tailor - Dragon City South

Required Items:
1. ** Wraith Robe
2. ** Lightning Leggings (Flowing Light)
3. ** Blood Staunching Sleeves
4. 10 pcs. Polished Lumber


Craftsman Quest

NPC: Craftsman - Dragon City South

Required Items:
1. ** Dragon Scale Necklace
2. ** Billow Pendant
3. ** Illusory Sky Ring
4. 10 pcs. Grindstone Powder


Pharmacist's Quest

NPC: Hua Ren (618, 390) - Dream City Suburb

The Quest is a bit different from the other three since you don't need to make any items.
Just visit the NPC and bring along 52,000 yuan to pay him for the book.