DonH;
I am not an authority on thermometers, however, my Lyman was so wildly inaccurate that I replaced it with a thermometer that I got from "The Antimony Man", Bill Ferguson.

Pure lead has a listed melting point. You might check that out (Google it) and of course, be sure that your "pure lead" is pure. Then bring some of the pure lead to up to melt temperature and measure the temperature.

Water only boils at 212 degrees at sea level. At higher elevations, it boils at a lower temperature. The 210 degrees you received is probably correct.

Dale53

I see it as sorta like certain other measuring tools. If you are using the same tool to measure all the time, you get a good relative comparison from batch to batch. You will doubtless, find that the temperature you cast at will vary a great deal from the temperature that someone else will find correct. 

Now, if you are having to, say, alloy the metal to have it melt at a particular temperature, to be confirmed by someone else... Then I would suggest a calibration approach using thermocouples and plotting of errors throughout the range of the temperatures that it requires.

FWIW the purveyors of inexpensive import tools often have a multimeter for sale that is set up to read a type K thermocouple. The one I have reads in celsius (make a conversion chart, or just use celsius) and will go to either 1400F or 1800f equivalent (not handy, cant check right now.)

Add a decent thermcouple probe to it and you can have an accurate measure of temperature if you feel the need.

Cheers
  Trevor Jones

I am intrigued. Exactly why do you need a thermometer? Am I missing something? After all, I've only been casting for 35 years.
Fred.

    I happened to be checking out a new electric pot and want to know how settings on the control correspond to actual temperatures. I don't use the thermometer very often, udually to verify alloy temps for my record keeping. I use a number of different moulds and some of them are pretty sensitive to temperatures they like to operate at. If another caster can use a one size fits all approach and get bullets to their satisfaction more power to them.
     I will recheck the Lyman but am inclined to think it matches that of Dale's experience as all three thermometers were at approximately the same depth in the melt when i took the readings. 100 degrees would be a lot of difference within the melted alloy.