Spin Flax is a Lunar spell, requiring the completion of Dream Mentor quest. When cast, it allows players to spin flax in their inventory into bowstrings. Each cast of the spell will use up 5 flax (or less depending on your inventory), producing the same number of bowstrings. When you cast the spell, it will automatically be cast enough times to spin all of the flax in your inventory. A full inventory of 25 flax takes around 7 seconds to spin.
For every 5 bowstrings made using the spell, players will make a net profit of -240 with only runes or 210 with a staff of air equipped.