On Thu, 05 Dec 2013 16:51:33 -0500, Emma Genius
wrote:

On 12/05/2013 03:22 PM, wrote:
I have a standard hand-held Benzomatic propane torch, probably 35+ years old. Fortunately I have never run out of gas in the middle of an important project, and I do have 3 hardware stores within a five minute drive. But I sometimes do projects late at nite after the stores would be closed, and it would be nice to know when my propane cylinder (~2.75" diameter, 11" long)is about to run out.
I could weigh an empty cylinder, but that could be tomorrow or late next year, I don't have a clue how much my present cylinder has been used. Ideas ???


Put the propane tank in the freezer for 30 minutes.

+1

Pull it out and start scanning the tank from top to bottom with an infrared thermometer.
As the tank warms up, you'll notice the temp changes drastically at the liquid level.

Breathe on it. The condensation line will show the level of the
liquid inside.


If you don't have an infrared thermometer, now you have a reason to go buy one.
And for the love of God, get a spare tank of propane while you're at the store. ;=)

;-)