|MLA Citation:||Bloomfield, Louis A. "Question 1217"|
How Everything Works 16 Aug 2018. 16 Aug 2018 <http://howeverythingworks.org/print1.php?QNum=1217>.
The process you describe, bending wood while heating the wood with steam, takes advantage of the fact that cellulose molecules bind strongly to water molecules and that the water molecules then lubricate the chains so that they can move relative to one another. Water is said to be a "plasticizer" for cellulose. Heat, water, and stress allow the cellulose chains to slide slowly across one another. With enough patience, the wood's internal structure can be changed forever. When the heat, water, and stress are then removed, the wood keeps its new shape.