Mastering the Flame.... indirectly

[ES Reuter]

Well,

As I posted in my intro I want to learn the in's and outs of fire. Today I took another step in the journey. Though not the first, my first step was the purchase of the grills, then making a 2 zone fire. Which, in my life was never even thought of, even on gas grills, my food was always either over cooked or burnt and raw on the inside. The two zone fire helped me over come that issue.

There are several other things i learned since getting into cooking on live fire much to what i owe here, leaving the food alone, keep the cover on, control air from the bottom, ect.

A big thanks to all the people who post their knowledge and experiences and also to the weber cook books by Jamie Purviance, what a great series eh? lots of good info there for the low man and I am sure there are things in there for the big man too.

I set out today to answer some questions I have with briquettes for a fuel source.

How many briquettes will get you what temp? There seems to be a great deal of info about lump charcoal on the naked whiz. Also I recall reading here about the difference of lump and Kingsford Blue, but I have not run across a chart or comparison about how many briquettes will give you what temp. If you the reader know of a deal of info please share, though i still want to burn and learn

So i decided to undertake this little venture and share it with all, even though many of you already know this, its for my sake too.


The experiment over all, burn a selected amount of whole briquettes and measure internal grill temps.

method:
measure time from lighting the paper in the chimney until grill reaches internal temp of 150ºf
Take temp reading every 5 mins
run the kettle with wide open vents, top and bottom.
never lift the lid until under 150ºf
shake ashes off and sweep at 60mins and 120mins into burn.
vents opposite fire
coals placed in char baskets
temp reading at 1.5" above grate

the variables:
as we all know there are too many variables to contend with when grilling in the real world. wind speed, humidity, sunshine placement of kettle.
for these elements we have to just give in to nature and label the out come of this experiment as a guide line and not exact data.
I will record a variable if it is very strong, such as a nasty wind, it started raining, large temp drop ect.

keeping consistent, as we all know the way to test and prove something is to only change one variable at a time. for the next few fires we will only change the number of coals for the burn. Everything else i will do my best to recreate it exactly as before, IE, placement of the basket, the vents, same thermo in the same place. you get the idea.

tools:
paper and clipbaord
iphone
6" bimetal thermo

i think that about sums up everything.
Enough with the talking, now the doing.
lets begin shall we,


Ahhhh, the way it should be every day. Cooking on the left and experimenting on the right.

Todays burn was 25 KB in my 22.5 kettle, coals in a char basket, vents open and top vent opposite the fire.
I was going to follow the instructions on the bag and have the coals in the chimney for 15 mins how ever after looking at the coals in the chimney it took only 6 minutes to get these coals red hot and the top few were red and grey. I had to scrub the idea that i would burn all the coals in the chimney for the same amount of time. Since this ignite took only 6 minutes to dump the coals i will estimate when i do 50 coals it will take about 12 mins but we will see when i do that burn.

my 6 minute figure come from when the paper in the bottom of the chimney caught fire to when i dumped them into the basket. not to much to comment on, looking into the chimney 25 coals is about 1/4 just enough to cover the wire support on the bottom. i had figured the coals would ignite fast, i was right.

this is immediately after i dumped the coals from the chimney there are 25 coals from paper ignition to dumping was a total of 6mins, then the cover was placed on the grill and the probe inserted

we are off! the learning run is off to the races

i decided to take a temp reading every 5 mins until the fire goes out. i chose this number simply because it would afford me the data to make a good chart afterwards.
some may say you need a digital thermo, to that i say, hold on, ill get there. Also, i tested the therm for accuracy in boiling water and its fine, on the mark.
plus as before we have to strive for general ideas here, as we can not control all the variables involved.

lets take a look at the chart

whew, well lots to talk about here.
first off i am happy, because my chart resembles other charts on burning charcoal and temps. since the ignition and the peak it is all down hill. As expected, the curve is true of a characteristic of a fire.

second observation is that KB under these conditions, has two plateaus, a peak internal temp of 375 for 10mins and then again at 200 for 15mins.

after looking at the temps and the times they stay there 25 coals is not really optimal for cooking indirectly, some things may work but burgers and other longer cooking item will not stay at proper temp long enough to be cooked safely.

another observation i made is, the hotter the fire the larger the fall in temp during temp taking intervals. the trend from a new hot fire dying out it typically loses ~15 degrees every 5mins.

the opposite is true during end of the fires life, at roughly 215 the temp drops change to about 5 degrees every 5 mins.
this phenomena intrigued me o at the lower temps i placed my had over the lid vent and noticed the amount of heat pouring out was drastically reduced as was the air flow. I have noticed several other times and while cooking with my 26 at hotter temps the air actually rushes out of the kettle.

I figure that this balance in temp is because of kettle design and weather inside the kettle. In this point of the fires life all the heat it pours out is almost dissipated by the environment in the kettle therefore creating balanced pressure in the kettle and in the atmosphere i live in.

this balance also slows airflow, with low air flow fire runs cooler thus kettle runs cooler, but there is enough draw to maintain the fire for longer periods. I believe the opposite is true with high temp younger fires, they are burning so hot and the pressure in the kettle is so great that air is being pushed out and sucked in aggressively thus feeding the fire and making it hot hot hot.

now, all that jazz you just read is my observation. I might be way off in my ideas, please correct me if i am wrong.

another observation i had was a shock. As with other charts out there many have reported a spike in temps after ashes are knocked off the coals. I did a knock and a sweep of the one touch system at 60mins and 120 mins. I stirred and swept after i took the reading so the temp change is reflected in the next 5 mins reading. 65mins and 125 mins respectively. The way i stirred the coals with out lifting the lid was dropping the front leg down on the ground a few times, it worked out fine and allowed me to never lift the lid.

the shock i had was at 60mins there was no real change after the knock and sweep in the temp only a slow down in the cooling of the fire occurred at 60 and 65 mins, going from 310 to 305, breaking the 10~15 degree decline. i can only suspect that having only 25 coals at this time in the burn they were pretty spread apart before i stirred them and cleaned the bowl so there really wasn't much of a change in the coal size and relation to each other.

it was at the 120 mins when i shook the coals again, and again with out lifting the lid off the bowl, that a temp spike occurred. this time i looked into the holes to see what was burning, the size and if they were still in a pile or all spread out.

here is the best shot i could muster thru the vents:

I could see that the coals were still piled together, though much much smaller with the ash knocked off they did receive more o2 and thus created a temp spike in the end of the fires life.

this little burn has raised many questions in my mind. when i burn 50 coals i am curious to see if there is a temp spike at the 60 mins mark as there will be 2 times the coals and ash.
will the fire burn for 4 hours? though i think not, most other research and kingsford themselves say you get about an hour to hour and a half out of a chimney.

another thought i had but not to change more than one variable, is when the coals are in the basket and clumped together they may burn a little cooler but do they burn longer at temp x?

these will be some things i will look into in future burns.

so finally here we are at the 150 mark. 160 mins from match light, i laughed as the temp in the kettle was still above the safe holding temp.

after a 160 min burn the coals were pretty much gone i think its safe to say that if you want to burn your coals to a safe put away temp it will take 3 hours. though there are a few coals with a little glow.

here is the coals in the basket after i opened the lid at 150 at the end of my burn.

i dumped the baskets out and here is the still lit embers

and again in the light so you can see whos who

 

[ES Reuter]

what did i learn from all of this?
to much to write about right now, and as with any good learning session i have more questions than answers.
i want to learn when times are right to add coals to maintain a temp, or what is the absolute last moment to add coals before it can not ignite itself. baahhh to many questions.

tomorrow i will have a 50 coal burn and record it in the same manner and we can compare results. i think it will be much less wordy, so you wont have to read so much.

I do thank you for reading this far. it was a great day and a great little burn.

i also just learned the 10k character limit.

stay tuned.

ESR

oh, hopefully all my grammar makes sense and there are minimal spelling errors, its late and i require sleep.

 

[Kevin L (NKY)]

I am looking forward to the continuing information this good to know, on burn time, amount of coals for a set temp is nice to know for for small/large cooks. I myself in the same boat for learning to cook with fire, I have been on a gas machine way to long and coal is so much different not only in flavor, but in constant temp is so much harder to achive with coal than a gasser. Coal is a art, that I am having fun to learn.

 

[John Bridgman]

Thanks for writing this. I had always wondered what the temp vs time chart would look like (since I do still sometimes come out and get surprised that the temps are 225 instead of 325) -- that's a really useful presentation.

I suspect that at 60 minutes there just wasn't enough ash to make a difference and that you'll see the same results with more coals. Just getting my bet in early

The chart I'm waiting for is the one that says "here are the adjustment times and (maybe) charcoal additions I needed to maintain a constant 325 or 350 for xxx hours". I can do that at 225-250 pretty easily (basically start with the vents almost closed and open as needed) but I'm not yet very good at keeping higher temps for long times.

 

[Bob Correll]

Erik,
With all due respect, it seems that you're trying to change an art into an exact science.
Will you need to do all this again when it's 20 degrees out, and/or windy?

Please don't let me rain on your charcoal with my comments, since I suspect it's a ton of fun doing this
And I do admit to only scanning your comments, so maybe it's me missing the boat, and it wouldn't be my first time.

 

[ES Reuter]

Bob,

Naaa, I am not trying to ruin my experience, I am trying to build a solid base for myself.

No cook will i count out coals i just fill the chimney light and go.

I feel by doing this i can get a visual reference for about this many coals looks like this in the chimney and when i pour them i can expect about temp X.

Nothing exact, its just several times i pour a chimney and expect a temp of 350 but got 550 or higher.

now i have come far enough to know to get from 550 to 350 just close the damper down and let the fire die off a bit.

like i said, i want to build a base so i can get a good idea of a rough temp for x coals and how long i have to cook on them

there is still plenty of room for the art

the next one will have much less words though, the first is always the longest.

esr

 

[Bob Correll]

Gotcha Erik!
When one has done something to the point of it being second nature, one can forget what it was like in the beginning.
Your method is no doubt better than my 'burn and learn' method was.

Now if I could just get the hang of computers, after about 17 years of trying to learn, and getting tempted to burn.

 

[ES Reuter]

I know exactly what you are talking about.

there are things in my profession i dont think about. its just do.

then sometimes when asked to explain, i get tripped up because its not a thinking matter.

esr

 

[Ron Snarski]

Actually, there does appear to be some missing information on your graph. I see no beverage consumption time-line in reference to the cooking time?

 

[Jim McKelvey]

Love this posr Erik. Looking forward to the next installment and thanks for taking the time!

 

[Gary S]

Gotcha Erik!
When one has done something to the point of it being second nature, one can forget what it was like in the beginning.
Your method is no doubt better than my 'burn and learn' method was.

Now if I could just get the hang of computers, after about 17 years of trying to learn, and getting tempted to burn.

Some of us older folkes just do things by feel. We check it when it feels about right ...plus or minus and adjust from there. It's called "experience"

 

[ES Reuter]

50 coals

well today i burned the 50 coals.

as i promised it will be shorter in word length, but hopefully rich in content

well as the title says its 50 coals this time.

I grabbed this little snapshot to help ya get a visual reference in your chimneys, you should note that i am using the weber chimney as i am not sure of the volume of other brands chimneys.

just counting and plunking the coals in the chimney will get you to cover the second air hole from the bottom and just touching the highest one. so roughly half a chimney, as i have read many times on other sites and info posts.

i am super happy because now i have a reference number for when i hear and see recipes that say use about a half a chimney.

i used the same timing and lighting method as yesterday, paper and matches.

I did have a thought in the back of my mind that perhaps twice the coals will make everything else double.

i was right on a few aspects of the burn.

the time from paper catching to dumping the coals this time was double. i dumped at almost the exact tick of 13 mins on the clock.

here is a snap shot of the coals at 6mins into the light, the same time 25 were ready to cook. as you can see these are not ready yet at all.

then we have the dump.

this is at 13 mins after fire ignition. coals are nice and ashed with a touch of black on some.
I decided to let the coals go until a certain point i feel they are burning as opposed to burning them all the same time. if it was 25 coals burned for 13 mins they would be half dead by the time i pour, and if i poured the 50 at 6 mins only half was lit so its a compromise.

the criteria i use to determine when they are dump worthy is flames come from the spaces between the coals, there is bright red in the spaces and the top coals must have white on the corners moving into the center, not just little white tips.

it is a variable, but a necessary evil. Plus like Bob and I discussed above, charcoal is a art and a process no need to be uber exact. just have fun and learn

well lets get on to the data.

lets rap.
well, as we all expected the temps will be higher.
buuuuut as in my mind with the light time being doubled, the coals being doubled i was curious, will the temp be doubled? nope, peak internal temp was 430ºf.
i think there just isnt enough air flow to a fire of this size to double in its btu output.

the second observation i noticed while doing the experiment, is 50 coals have longer plateaus there are 2 big temp stalls in this burn as noted at 405f and 235f.
25 coals did not have this long of temp holding.

a third thing that came true from last nights writing is that, well, the fire did burn nearly 4 hours. makes me a might bit nervous to burn 100 coals, will it be 8 hours?
now that time is obviously not the cooking time but the time from dumping to 150 and opening the lid.

as seen on the chart you get about 30 mins cooking at 400f, since i ran everything wide open with some air control i would estimate you can get a good 45~60 mins at 350. possibly more.

after that 30mins at 405 the fire goes into decline. like yesterday i bumped and swept the ashes every hour on the hour. Like the 25 i did not get a spike until the end of the fires life. actually when i swept and stoked the coals, that put the fire in rapid decline. as noted at 60 mins and again at 120 mins.

at 60mins the fire was 375, i shook and swept ashes, then the fire reported 345. at 120 we have a slide from 270 to 235. i wonder if its because the ashes actually insulate the fire and hold more heat at these points. then when the ash is removed the fire burns better but it has lost its big layer of insulation. that is the thought in my head, help out if you know the answer.

again the phenomena at the end of the fires life when ashes are swept we get the spike.
well, i dont know what to think. Perhaps with the insulation theory when the fire is strong it has enough energy to provide the kettle and the ashes with heat, however, later when the fire is weak the ash finally absorbs and dissipates the heat before the kettle gets it.

any thoughts?

thats about it for observations, the rest of the burn was pretty similar to the 25, it just burnt out.

i will say this, KB and weber both are efficient this is all that was left after i lifted the lid right when we hit the 150f mark.

and check out the actual still burning coals

pretty efficient eh?

ooo. ten photo limit, including smilies. better make part 2.

see ya there!

 

[Jon Des.]

Great idea Erik, and my inner geek is really enjoying the scientific method popping up around here lately.

I suspect the late spike after sweeping ashes is due to increased airflow through the bottom damper. Same reason that your peak temps were the same in both trials.

A word of caution should you expand this to other brands: you may need to weigh your batches of KB and go by weight for other brands. Stubbs and RO are both larger and heavier, so 25/50 coals will have a lot more volume, mass and surface area.

Keep at it - this is good stuff!

 

[ES Reuter]

50 coals part 2

well this time i ran out of space for photos!

at least its not words.

i didnt make a plan to measure ashes but i snapped a photo for all you OTG owners out there

you can expect about 1/4 a pan full of ashes from 50 coals.

so lets compare burns!

well like i said before some things doubled and some didnt.
Time of burn sure did

new things are the plateaus.

a recurring thing in both burns is the slide in temp when the sweep and stoke the fire while it is still strong.
the 25 coal line shows a slide at 60mins from 305 down to 260. while the 50 coals have two slides most notably at 60 mins going from 395 to 325.

the spike returns! at the end of each fires life, i noted interestingly they both occurred at roughly 190f.

something i just noted, the 50 coal fire did not have a rise in the temp after i dumped it like the 25 coal fire. I wonder if the 50 coals ate up the oxy in the kettle and started the air flow, therefore evening out the burn right away.
where as the 25 coals had a kettle full of oxy to burn first and then started the air flow. interesting.
it might be that the coals were all properly lit and maybe the 25 had some more igniting to do. meh, one of those things

well, some trends are starting to show, lets see if we can confirm them in a third burn.
lets look for slides when we stoke and sweep ashes on a strong fire.
the spike at the end of the fires life
and (gosh i hope not) doubled burn time

i am busy tomorrow so i dont think i will get to have a possible 8 hours to monitor a fire, i am free for friday so ill see if i cant make it happen then, barring any harsh environment change.

stay tuned! as we continue to master the flame.

 

[Kevin L (NKY)]

Eric;

Great graph really shows what,& where things are happing, can't wait for the 100 run. This alone is going to clear up some question I have had with my slow cooks. tonight chicken.

 

[John Bridgman]

so lets compare burns!

I read through the entire thread thinking "both charts on the same page... both charts on the same page... c'mon, just put both charts on the same page..."

Thank you !!

I think I'll print this off and tape it to the side of my Performer, just like the range card on my rifle

 

[ES Reuter]

I read through the entire thread thinking "both charts on the same page... both charts on the same page... c'mon, just put both charts on the same page..."

Thank you !!

I think I'll print this off and tape it to the side of my Performer, just like the range card on my rifle

no problem john, i am glad to be helping others out in my journey.
there will be a third chart with the 100 coals.

and that one will be the final in this first part of mastering the flame. i felt these three amounts of coals are the most frequent i use and have noted in recipes. there are other aspects of the flame i want to get intune with and i will post those test results.

i do ask this please remember that these are my results using my geographical and weather conditions plus i am using my measuring gear too. Some one with a spendy thermoworks probe will most likely find more accurate temps than mine.

also that you use the information like i am, as a general guide line. i dont want to you print it and use it as law, when cooking going ok time is this so i should have this temp exactly.

so far though we can count on the characteristics of the curves. steady decline, valleys and the end of the line spike.


thank you for reading

esr

 

[Jon Des.]

Your results are pretty linear, although I think the charcoal baskets may influence the results - at least as compared to just a mound of coals in the middle. I'd suspect the airflow is more limited in the baskets, which is causing your plateaus. When the ash sweeper lets new air in you're getting your spikes.

It's also really interesting that double the coals only yields temperatures about 50-75 degrees higher, but a longer cook. I can't wait to see what 100 coals looks like.

Question: does your Excel allow you to add a line down the middle of each that would "normalize" the points a little? It looks to me like the 50 and 100 graphs are almost the same, obviously with the 50 line shifted higher and right, but I can't tell if the slopes are really the same or diverging. I think that would tell us a lot.

 

[ES Reuter]

John,

Agreed, I had a thought in my brain to rerun this experiment with coals not in a basket but piles on the grate. Then i thought of the same thing but at half damper, then a quarter damper, all useful but the amount of things a guy can do and measure would make kingsford a killing and i would never get to cook anything.
but in due time my friend, later on we can do other experiments.

I will try to get the lines marking the points for you, but i can not lie, the 25 coals chart is the first ever chart i made in xls in my life. it took me a while to figure it out.

esr

 

[ES Reuter]

Is this what you meant?

let me know.

esr