Lump Trivia ... That Sinking Feeling

Jeepster47

Have you run out of lump during a cook?  Taken ugly daisy off, opened up the bottom vent fully, opened up the screen, and still the temp continued to drop?  You looked in the fire bowl and saw lump burning away, but the temp was still dropping?  What the heck?

When you run out of gas in a vehicle you're able to maintain full speed right up to the last drop.  Unfortunately that doesn't happen with the egg.  There needs to be a some unknown amount of lump burning merrily away to hold the egg at temp ... a partially filled tank if you will.  Have you ever wondered what the minimum amount of lump - normal cook - is necessary to maintain 250 degrees in a large egg?  Well, you're probably in the minority, but stay tuned anyway.

The KAB was partially filled with new Rockwood lump.  The KAB was used as a screen to remove any dust, fines or rocks from the fill.  A Flame Boss 200 was used for control ... it makes for a more consistent/repeatable test. Here's what "oh sh*t" looks like on the graph:

The "cook" stabilized and was going great until a little before noon when the fan started to work a little harder ... probably would have had to start adjusting the bottom vent if running manually.  The pit temp continued to look acceptable until about 12:30 when the temp began struggling to keep up ... fan was working harder than normal at this point.  At about 1:10 the controller knew the cook was in trouble and turned the fan on 100% of the time.  But, the temp kept dropping until it was obvious that this cook was done for.  I chose 20 degrees below the pit target temp as an arbitrary "cooks over" point.

Took a quick picture of the lump in the KAB and then dumped it into a seal-able one gallon container.  After the lump was cool, the ash was brushed off and the lump was weighted.  There was 1 pound 1.3 oz of lump left after the fire went out.

It was a good burn, the fire went straight down thru the center of the lump to the basket.  Then it started burning towards the right rear corner before it ran out of steam.

This is a single test sample ... no least squared analysis of multiple test samples ... it's not worth the effort.  Just remember that there will be one pound of lump left over when/if you run out of fire on a 250 degree cook.  That's over two hours of cooking that you might have planned on getting out of your fill, but didn't get!

PS ... I did a comparable test at 350 degrees.  Because the egg needs more heat for 350 degrees, the fire spreads out more and doesn't burn down through the center of the lump like it did above.  I forgot to take a picture before I disturbed the KAB, but you can still see that most of the lump is burning.  There was 5.6 oz of lump left ... considerably less than with the 250 degree test.



One other observation ... notice the amount of fine ash spread throughout the egg on both "cooks."  I would suggest that that is the result of having less than a pound of lump in the basket to diffuse airflow and having the blower running at 100%.  Thus, the final conclusion is to fill the egg with more lump than you think/know you need to prevent that sinking feeling and the salting of your protein with ash if the fire goes out when running a controller.