After completing Chapter 5 story missions, a quest in the Gerudo region called "Caring for the Statues" provides the ability to remove weapon seals. Complete this quest and go to the Blacksmith. A "Remove Seals" feature is available. Removing seals costs materials and rupees. Complete the quest "Secret of the Rito Artisans" in the Hebra region to give you the ability to remove all weapon seals.