On Thu, 4 Jun 2015 07:47:39 -0700 (PDT), rangerssuck
wrote:

On Thursday, June 4, 2015 at 8:06:17 AM UTC-4, John B. wrote:

It is easy to do,
just paint the area with a marker - permanent or white board - and
then heat the area with a torch until the marker goes away.

Interesting - i'd never heard of using a marker as a heat indicator. Any idea what temperature that "vanishing point" would indicate?

I've always used these: http://www.tempil.com/products/tempilstik-original/

No idea, but you can also "smoke" the area with an acetylene torch
with a very rich flame... or even a candle :-)

I suggested the markers because (1) it works and (2) you might not
have an acetylene torch :-)
--
cheers,

John B.