Old timers spent much time looking for the choice piece of wood that would not break when it was bent. Steaming When wood is dry it isn't very flexible. Wetting the wood helps the bending process. Steaming helps even more. However, there are advantages and disadvantages of each.
Some people say that steaming weakens the wood.
Many people wrap the birch with a hot steamy towel as it comes out of the steamer. This keeps it from drying and cooling until bending is complete. It is important to bend the wood gently, flexing it gradually, being careful not to bend too much in one place. If there is a spot that doesn't want to bend, we put it over our knee at that place and gently flex it. If it still doesn't bend, we take a timeout, and thin it at that spot with a hand plane or knife.