We have evaluated the potential of nuclear magnetic resonance (NMR) spectroscopy based on small portable magnets for in situ assessment of moisture protective properties of wood coatings. Low field 1H NMR with a unilateral permanent magnet was used to monitor and map the local moisture content (MC) of wood specimens uncoated or coated with various types of commercial paint systems. The MC beneath a coating layer was measured with a penetration depth up to 5 mm and with a depth resolution of 0.2 mm. The method is quick, noninvasive, simple to perform, and does not require removing wooden parts from the structure.
Pourmand, P., Wang, L. & Dvinskikh, S.V. Assessment of moisture protective properties of wood coatings by a portable NMR sensor. J Coat Technol Res 8, 649–654 (2011). https://doi.org/10.1007/s11998-011-9348-8