Trouvé sur un site :
"Reverse Engineering
It is important not to sell the items you create, at least when you first learn them. Instead, reverse engineer them. By doing so you will reclaim some of the materials used in making it, and you can learn a better version of the recipe. For example: A green recipe item reverse engineered can give you a blue version of the same recipe, and a blue recipe item when reverse engineered can give a purple version recipe. This is not guaranteed every time, and it may take you a few tries to get the upgraded recipes. The higher quality the recipe, the more difficult it is to learn through reverse engineering."