Wednesday, June 27, 2007

Why sanding back is a bad idea

One project I was sort of interested but never really had time to tackle was the quantitative analysis of the metal content of paint. The following is a depth profile of a paint chip from our home renovations last year. As time progresses, the back ground gives way to the signal from the surface layer, and the next two coats of paint beneath.

Figuring out how to standardize is a royal pain, but a qualitative glance at the measurement shows that the various highly toxic metals have much higher concentrations in the older paint layers than the most recent layer. This is why health professionals recommend that home renovators simply paint over old paint, instead of sanding it. Sanding the paint off releases all these goodies into the air, where they can be breathed, eaten, or otherwise ingested.

Our house was built in the early 70’s. I don’t know how many times it was painted since then, but even without rigorous standardization, it is obvious that paint has become a whole lot less toxic over the lifetime of the building.

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