A customer asked me how to tell if his pyrometer was reading the accurate temperature of his kiln. He said he heard something about a melting wick gauge. I searched and searched and did not find this.
I did find lots of other interesting info.
First, just in case you do not know, this is what a pyrometer looks like. The metal stick part sticks into your kiln where it is reading the temperature. If things don’t seem right, you could try adjusting it. 
On the site Lampwork Etc., I did find some interesting comments. Here are some things folks on the site suggested.
1. Take a penny (must be 1983 or later) and put it in your cold kiln, preferably just teetering off the edge of a small support or propped up on a piece of glass. Bring the kiln up to about 700 degrees, then slowly ramp it up from there, periodically peeking inside. The penny will turn black and go limp at exactly 787 degrees (when the zinc core melts). This will give you a good indication of how far off your temperature gauge is. Make sure you put protection down, so you don’t have a penny stuck to your shelf. If you want to see if one section is hotter than others, put several pennies here and there.
2. Stick a barbecue grill thermometer in there.
3. You can calibrate with water. At sea level water boils at 212 degrees.
4. You can use ceramic cones to check your kiln temperature.
5. I also read that when your temperature reading is over 50 degrees above or below the true room temperature it is time for a new thermocouple.