Unless there is enough lead in the paint to make it conductive, I wouldn't expect it to block microwaves. Remember that ground penetrating radar can easily get through the few feet of soil that is very effective at blocking gamma rays (by 99.9% or 10 half thicknesses.)
Note that many common materials which are effective at blocking gamma rays, like concrete, may emit low levels of radiation themselves.
I wonder, when used as paint, does it act like a kind of continuous Faraday Cage? Especially if painted inside and outside of the walls, with a gap in between.
Lead is very effective at stopping X-rays. At 100keV half thickness is 0.12mm. A layer of paint might have a measurable effect. Gamma rays are another story. At 500keV half thickness is 4.2mm. https://www.nuclear-power.com/nuclear-power/reactor-physics/interaction-radiation-matter/interaction-gamma-radiation-matter/gamma-ray-attenuation/half-value-layer/
Unless there is enough lead in the paint to make it conductive, I wouldn't expect it to block microwaves. Remember that ground penetrating radar can easily get through the few feet of soil that is very effective at blocking gamma rays (by 99.9% or 10 half thicknesses.)
Note that many common materials which are effective at blocking gamma rays, like concrete, may emit low levels of radiation themselves.
Wow. I didn’t realise it could be that thin.
I wonder, when used as paint, does it act like a kind of continuous Faraday Cage? Especially if painted inside and outside of the walls, with a gap in between.