Why is my COWW melting at 500 deg?

[Rio]

I have been melting COWW for a while now and sorting wears me out. So I smelt as low of a temp as I can which takes a long time as opposed to my known clean stuff that I pour the heat to and get knocked out. So to be cautious I picked up a thermometer and the COWW according to the thermo is melting at 500 deg. I skimm off the non lead and take it on up to almost 600 then ladle it out into ingots. Don't get me wrong at 500 it is barely fluid. At 600 it ladles and pours easily.
Always possible the new thermo is **** as well.

[OBIII]

Check your thermometer both in ice water and boiling water. This will tell you how close it is or is not.

Pure Lead 621 F
Zinc 787 F
Tin 449 F
Pewter 338-446 F
If you have any of the above, turning the temp until it just begins to melt will further allow you to calibrate your thermometer. (Or you could
just buy one of my PID units. )
OB

[OS OK]

Check it in boiling water.
To calibrate, hold the shaft firmly behind the round case and with the other hand rotate the case to correspond, re-check and keep adjusting until you are satisfied.
This is the nature if a bimetallic spring type thermometer.

[Rio]

Oh I want a pid,, just gotta find a pot big enough for my needs. Ok I will try checking

[JonB_in_Glencoe]

WHY ?
Melt temp from http://www.lasc.us/CastBulletNotes.htm

WW (clip-on)

463 degrees slushy To 505 degrees molten

[Oklahoma Rebel]

that's surprising, didn't think WW's were that low, I thought they would be at like 650-675

[pjames32]

I don't think you have a problem. Sounds about right!

[quail4jake]

Great to know, thanks Jon B.!

[Grmps]

often we tend to over-think things. But, many thermometers have a tendency to be way off. (like my Lyman) so I built a PID