Here is a thermocouple as received from Omega, except I think I did trim back the outer insulation a little. This images is made with a scanner.
This TC is presently gummed up thanks to my using Band-Aids at high temperatures, but it still agrees with the other instruments. The use of Band-Aids in calorimetry is "highly unusual" (as you said) and not recommended. But these little things are robust. You can get away with all kinds of mischief and still get the right answer. As I said, try one! I think it is a mistake for you to make assertions about what is usual or unusual, or about the role of trapped air, or what-have-you, unless you have tried using TCs in various ways. As I said, I have used them with everything from roast turkey, to fish pond water, to taking my own temperature as a fever thermometer. They take a beating and keep on ticking. (Granted, I use the shielded one for turkey and fudge.) These things go up to incredibly high temperatures. Never had a use for that. - Jed
<<attachment: Thermocouple as received.jpg>>
