Bi Fang was highly action-oriented; after a brief respite, he began his "wall" project.
Actually, it was quite simple: just dig a trench around the cabin, then sprinkle it with a mixture of ice water mixed with sawdust.
In extreme temperatures, this mixture would almost instantly freeze into blocks of ice, quickly forming an impenetrable wall.
"Ice is a solid formed from water, and thin ice shatters like glass at the slightest touch, which is common knowledge. However, the fact that ice can be as hard as steel and as solid as concrete is something many people do not know," he explained.
"In fact, it's quite simple to achieve this, just add some sawdust," he said.
"Adding sawdust to ice blocks may sound absurd, but it actually has a professional name: Pykrete, a type of composite material, similar to reinforced concrete, which is a combination of cement and steel."
