…asks reader Jason. That’s an excellent question and I confess I don’t know the answer. I understand that different types of wood have different insulating properties once they’re pulped and frozen. What I do know is that the prototype pykrete ship that was made in Canada in the spring of 1943 stayed frozen all summer with the help of the 1 horsepower refrigeration unit that was installed onboard. When the project was abandoned later that year the ship was simply left by the shore of Patricia Lake. With the Canadian cold it lasted all through the winter and early spring, but was completely melted by the end of the summer of 1944.