porous structure – Molecular Wall Lab

Where Odor Molecules Hide Inside a Wall: A Depth Map

kawai1104 / 2026年7月27日

Last July, I opened a vacant apartment I manage and stopped in the doorway. The smell was not stale air. It was something organic — faint, but unmistakably biological. I opened the windows for hours. By evening it was nearly gone. The next morning, it was back. That returning smell is the problem I cannot stop thinking about. Odor molecules did not disappear. They came back from inside the wall. This article is my attempt to map where, exactly, they go — and why standard cleaning, ventilation, and even full wallpaper replacement cannot reach them. The answer points directly at the same porous structure that makes gypsum board valuable in the first place.

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Research Note #23: What Dry Construction Gave Up

kawai1104 / 2026年7月24日

In autumn 2019, during renovation of an 18-year-old property, I peeled back wallpaper and found uniform brown staining across the entire back surface. That moment made me look seriously at gypsum board for the first time. Dry construction methods replaced wet plaster with boards and wallpaper, cutting build time from weeks to days. Efficient. But gypsum board is a porous material — it absorbs moisture and releases it, which is why interior humidity stays relatively stable across seasons. The problem is that the same porous structure absorbs odor molecules and VOCs with equal indifference. The moisture-regulating property and the odor-accumulation problem are not separate issues. They come from the same physical structure. That is the paradox I keep returning to — and I still have no clean answer for it.

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Pyramid Gypsum: What Ancient Builders Already Knew

kawai1104 / 2026年7月22日

Ancient Egyptians used natural gypsum mortar between limestone blocks at Giza — 4,500 years ago. They chose it for a reason that still matters today. The porous microstructure of calcium sulfate absorbs small movements and humidity fluctuations, buffering stress at every joint. Modern gypsum board works on exactly the same principle. That porous structure lets walls breathe, absorbing moisture when humidity rises and releasing it when the air dries. It is gypsum’s greatest strength. But those same pores do not discriminate. Tobacco compounds, cooking vapors, ammonia-based biological residues — they enter the same way water vapor does, then adsorb to the pore walls and stay. The ancient builders never faced this problem. The desert air gave them only moisture to manage. We are not that fortunate.