The Science Behind The T-Rex Steak

TNW was kind enough to post my report on his site a few months ago about some heat damage that occurred to my new custom egg table, and a lot of research that I did to determine the proper base for my large egg to resolve the problem. I modified my table as shown in the report and I haven’t had any trouble since then but I was still wondering just how hot various spots on the egg would really get during a typical high-temperature cook like T-rex steaks. So I decided to run some more tests to find out.

First I purchased a digital Fluke thermocouple meter with ten Type-K thermocouple heat sensors that are rated up to 2000°F. This equipment came from a Sun Microsystems laboratory and it was certified for accuracy, and the sensors were brand new so I knew that the readings would be reliable. It took a while for me to find the instruction manual, figure out how to program the meter, and build three wiring block harnesses to connect all of the sensors but I just finished it tonight and tested it out. Everything works perfectly.

The T-Rex Test:

I went out to the egg table around 5:30 pm and connected the thermocouple heat sensors to various spots on the interior and exterior of the egg. I used thin aluminum adhesive tape to hold the sensors to the outside of the egg and I also connected a few sensors to my firebrick base. Then I took an initial reading of all the sensors before I lit the egg. They were all within 2°F of the outdoor temperature so I had a green light to proceed. Here are some photos of the egg wired and ready for takeoff:







For this test I decided to cook the steaks exactly like I normally do; no deviations at all from my normal T-Rex cooking routine. I started with a nearly full load of Wicked Good Charcoal, bottom vent wide open, top vent wide open, and a stainless steel fine mesh strainer set over the top vent to contain sparks. I lit the egg with rubbing alcohol and proceeded to take temperature readings every 5 minutes during the warm up and cooking cycle. After the steaks were on I closed the bottom vent halfway but made no other adjustments. I flipped the steaks once after 5 minutes and removed them after 10 minutes. I closed the bottom vent all the way and then placed the ceramic cap on top to shut the egg down. I took additional temperature readings for several hours after the egg was shut down. The resulting temperature readings can be seen in the graphs below. Click here for the Excel file which contains the graphs and all related data.





Observations:

The exterior of the egg does indeed get quite hot with peaks as high as 400°F. The bottom of the egg is actually one of the hottest exterior spots which confirms my initial research and testing; however there are a few other spots which get almost as hot so we need to be very careful around an egg that has been cooking for a while at moderate to high temperatures.

The interior egg temperatures all followed the same basic curve with the exception of the bottom which got hotter faster and was at times even hotter than the heat exiting from the top vent. This is further evidence why it is so important to select the proper base for the egg, especially when you are mounting the egg inside a table.

The ceramic feet obviously did a great job of keeping heat away from the support base with the firebrick being more than 200°F cooler than the egg base at peak temperatures. In fact the bottom of the firebrick actually got slightly colder during the first hour while the egg was heating up, which I suspect was due to a slight draft of cooler outside air being drawn into the table as the lump started to catch. But then the firebrick heated rapidly during the last 2 hours even as the egg was cooling down, apparently because it was absorbing the heat from the exterior of the egg and holding it almost as long as the egg itself. So the air gap created by the feet is critical but it alone is not enough. A substantial support base is still required to handle temperatures which approach and exceed the UL-recommended maximum temperature threshold for wood surfaces adjacent to heating devices in residential areas (see my other report for details).

Another surprise was that the grate was actually the lowest interior temperature but I suspect this was partially due to the placement of the grate sensor near the inside rim of the egg. I would have liked to place it in the center of the grate but I didn’t have the high temp. protective sleeving on hand yet to protect the sensor wire and I didn’t want to ruin the sensor so early in my testing.

This test has convinced me that the air gap between the egg and base is even more critical than I originally thought, as is the air circulation around the egg and support base. All the more reason for everyone to be super careful about how we design our tables and what we decide to place under or near our eggs. I can’t draw too many other conclusions yet but I will perform more testing and let you know how it turns out. By all means share your thoughts and feedback, especially if you have a Stoker and have conducted similar tests.