Ash Buildup in Chimney Elbows, and Infra-Red Thermometer

Bumped the botom of the elbow on the back of my boiler yesterday, it was cold.

When I used the Infra-Red thermometer the top of the elbow was hot and the bottom cold with a fairly distinct line between the two. In fact I then used my hand and slid it from the bottom of the pipe around to the top until the pipe was to hot.

This as it turns out was a very acurate indication of ash level in the elbow.

I didn't really need the thermometer, just a carfull intital touch on the bottom of the pipe.

Anyone else have succes with this noninvasive test.