Can you melt a wooden log?

Joyce Cheng | May 1, 2010

Can you melt a wooden log?

Melting is a physical process that results in a phase transition from solid to liquid. When the temperature is raised to a substance’s melting point, the vibrational energies of the molecules exceed the stabilization energy of the solid-state lattice arrangement, and the molecules break free from the lattice into a less ordered state – the liquid. In order for wood to melt, it must go through this process.

When a substance undergoes a phase change such as melting, its chemical makeup remains the same. For example, both ice and water are chemically the substance: H2O. However, when heat is added to wood, the wood oxidizes before it would be able to melt. Composed primarily of cellulose, lignin, water, and several other materials, wood contains long-chain organic molecules that decompose into products such as charcoal, water, methanol, and carbon dioxide upon heating. The physical structure of wood is destroyed in the process, and the resulting material cannot return to the original matter. As a result of the chemical, irreversible breakdown of its components, wood does not melt.

What if you tried melting wood in a vacuum, where there is no oxygen to begin the oxidation process? This clever idea still fails. Although the water and volatile matter would evaporate in the vacuum, the long cellulose fibers in wood would strongly inhibit wood’s transition to the liquid state. Heat might break the carbonyl bonds in cellulose, leaving behind carbon in charcoal form or carbon dioxide.

In theory, it may be possible to melt wood by one alternative means. At standard temperature and pressure, the melting point of carbon is 3500oC. If this could be lowered to a temperature that could be attained experimentally, the wood might be able to melt. Although facilities capable of creating such conditions exist, there is no published literature that has tested this hypothesis. Thus, until science indicates that it is possible, the answer to the question, “can we melt a wooden log?” will remain a no.