My egg self ignited the day after a cook

zaphod · October 7

The timeline:

5pm Sunday
finished the enchiladas/nachos, (indirect cook at 350F)
closed off the vents, exchanged the reggulator for the ceramic green snuffer cap
put the reggulator and unused grills into the egg and closed the dome

9:20pm Sunday
egg is cool enough to drop the side mates so the don't get wet from condensation overnight
check the top dome and sides with my bare hands - very cool, almost enough for a cover

5pm Monday
opened the egg to start cleaning it, removed the plate setter
supper was ready, went in and left the dome wide open

5:30pm Monday
My wife commented that she could smell smoke
I thought it was just the ash blowing up, looked at the egg and saw "smoke" - just the ash I thought.
I went out to finish cleaning and the lump was lit and burning, I was looking into a pile of red coals about 7" in diameter and VERY hot.

Closed the dome and the temp gauge popped up to 300F. This was an active fire. The dome and sides were now *hot*

------------------------------------------------------------

so, I'll start with WTF?

This was a dead cold fire that had been snuffed for 24 hours. I took a picture just after I removed the platesetter because the black soot marks on the fire ring lift points was a new thing to me.

Image: https://us.v-cdn.net/5017260/uploads/editor/qb/ed0d707su7rj.jpg

There is no fire there. 30 minutes later, I had a bed of coals I could cook on. I did not take a picture, I just closed the dome and walked away.

I know that an open dome is a great source of oxygen (think wok cooks when you close the bottom vent and the fire keeps going), but you need a spark to get going.

Obviously the fire did not go out.

My felt is a couple of years old and pretty compressed, maybe I am not getting a good seal
the black soot at the top/bottom the picture at what I use for grab points on the fire ring is new, I have never seen that - Do I have an air leak and that is where the air was going to keep a spark lit?

like I said, the egg was cool last night just after 9. Temperature was below 100F and cold/cool to the touch.

I feel very lucky right now.

zaphod · October 7

cleaned off the ring, put back the platesetter and reggulator inside, snuffer cap on top. Exactly the same set up as when I shut it down yesterday. Temperature is down around 150F.

will see what it looks like tomorrow afternoon, and what happens when I lift the dome for 30min. I'll take some temperature readings before I do that so see how cold it is/isn't.

DoubleEgger · October 7

I’d pull the fire bowl and give everything a good cleaning and check for base cracks. That black looks like fines to me.

kl8ton · October 7

My first thought is to check the base for a crack.

Edit: Well I see DoubleEgger already recommended this while I was typing and rereading your post to see if a crack check was mentioned.

zaphod · October 7

I'm off tomorrow, so i'll spend the afternoon doing an examination of the base, will have to find a place to put the fire basket full of potentially still smoldering lump while I do that. not above using a bucket of water to store it.

zaphod · October 7

DoubleEgger said:

I’d pull the fire bowl and give everything a good cleaning and check for base cracks. That black looks like fines to me.

"fines"? I don't get what you mean.

Buckwoody Egger · October 7

https://eggheadforum.com/discussion/1175502/survey-how-long-does-your-charcoal-take-to-extinguish

hope you find how the charcoal was still able to get a little bit of oxygen

definitely alarming that it reignited when opened. seems like it wouldn’t have been able to get enough oxygen to get a large fire going in the closed egg

but yes, definitely worth evaluating your seal.

what is the make of that metal fire basket? it doesn’t look stock. while it looks inefficient with the small holes, it also looks like it could keep a bed of ash mixed with fuel. seems like it would be better to have ash fall away from the fuel for less smoldering.

DoubleEgger · October 7

zaphod said:

DoubleEgger said:

I’d pull the fire bowl and give everything a good cleaning and check for base cracks. That black looks like fines to me.

"fines"? I don't get what you mean.

Industry term for fine particles of charcoal.

Fines have a lot of uses.

https://www.dorsetcharcoal.co.uk/industrial-charcoal-fines

zaphod · October 7

DoubleEgger said:

zaphod said:

DoubleEgger said:

I’d pull the fire bowl and give everything a good cleaning and check for base cracks. That black looks like fines to me.

"fines"? I don't get what you mean.

Industry term for fine particles of charcoal.

Fines have a lot of uses.

https://www.dorsetcharcoal.co.uk/industrial-charcoal-fines

interesting - thank you.

zaphod · October 7

Buckwoody Egger said:

https://eggheadforum.com/discussion/1175502/survey-how-long-does-your-charcoal-take-to-extinguish

hope you find how the charcoal was still able to get a little bit of oxygen

definitely alarming that it reignited when opened. seems like it wouldn’t have been able to get enough oxygen to get a large fire going in the closed egg

but yes, definitely worth evaluating your seal.

when I was a kid camping we'd look for an ember on a log from the fire from the night before, and get the fire going with some newspaper and gentle blowing. Had the same fire go for over a week once.

I suspect that the same thing happened with this fire. just enough air to keep an ember and then off she goes when I left the dome wide open for 30 minutes.

Buckwoody Egger said:

what is the make of that metal fire basket? it doesn’t look stock. while it looks inefficient with the small holes, it also looks like it could keep a bed of ash mixed with fuel. seems like it would be better to have ash fall away from the fuel for less smoldering.

the basket is BGE brand, about 3 years old. After almost every burn, the next morning or afternoon I stir and shake out the basket to get out the loose ash, then put the basket on some racks while I clean the egg. I sweep out the entire egg and then remove all the ash and dump it into the compost[1] before refilling with new lump. If I haven't let the egg cool overnight I put the ash pan into the egg and then dump into the compost the next day in the case they aren't a cold as they should be.

That old lump sits in the open air for 10 or 15 minutes while I sweep, clean, dump, and fetch the charcoal bag. Not once have I ever detected any hint of it warming up or reigniting.

right now, after 3 1/2 hours the egg is cold both to touch and dial.

Image: https://us.v-cdn.net/5017260/uploads/editor/fb/3jlu5jpzs1l0.jpg

[1] Obviously right now I'm rethinking the "dump it into the compost" part.

Buckwoody Egger · October 7

ok I see the stainless fire bowl for sale in us and canada— and that the holes are bigger on the bottom - and they say “

Designed to replace the cast iron fire grate with the same hole geometry

https://biggreenegg.ca/products/stainless-steel-fire-bowls

so i retract my “inefficient” observation!

my ash futzing process is always pre-cook and rarely on consecutive days. thanks for sharing your experience and campfire story recall. if embers can reignite in that situation the egg is certainly a conducive environment.

zaphod · October 7

I'll be recreating what happened yesterday to see if I get another ignite, and I'll be doing a dollar bill test, some temperature readings with the inkbird, and an inspection for a crack in the base. Good thing I'm not "working" today.

fishlessman · October 7

check the silicone seal on the lower vent, its a low temp silicon. ive seen that fail before. it splits, peels back etc. that keeps the air supply down low and if the grid level seal has the slightest leak you get an air flow bottom up

zaphod · October 7

thanks, I'll add a check of the seal to today's inspection.

zaphod · October 7

Buckwoody Egger said:

my ash futzing process is always pre-cook and rarely on consecutive days. thanks for sharing your experience and campfire story recall. if embers can reignite in that situation the egg is certainly a conducive environment.

I like having the egg ready to go at a moment's notice. some days the traffic is light and I get home in time to suggest a cook for supper. I like the spontaneity that a ready egg gives me.

Canugghead · October 7

You may want to try this also... when it's dark outside, empty the Egg and stick a high wattage incandescent bulb in it, run the cable through the bottom vent and seal it with tape. It's a long shot but it may shed some light on the problem.

ColbyLang · October 7

Literally

zaphod · October 7

what I did today ....

took temperatures of the lump this morning
left the dome open for 30 minutes or so (sitting close by)
took temperatures again, same - so no self ignition today
tore apart the egg today and cleaned it up
rubbed down the inside of the bottom dome with towels, removed ALL the ash/fines
cleaned out the runners of the bottom vent so that it closed firmly all the way
took a 100w equiv light and examined the inside - no visible cracks
did a dollar bill test - passed
closed the dome, removed the reggulator and peered down the top as I waved the light bulb around the bottom vent - saw a bit of light
taped shut the bottom vent with black duct tape to see if the seal was leaking light - seems to be leaking

but

the silicone seal for the vent is translucent and I think that what I saw was the light coming through the silicone conclusion? dunno, more of a confusion than a conclusion.

I reassembled the ceramics, filled up the basket and will have another cook for supper. Tomorrow when I get back from work I'll do another temp check for warm lump and see what leaving the dome open does to it.

vent taping:

Image: https://us.v-cdn.net/5017260/uploads/editor/im/qr4ldg1hblxl.jpg

when I tested, the lightbulb was above the vent, and you can see an ambient glow even before I start waving the light at the vent. I didn't see a shaft of light at anytime, only ambient glowing.

link to light test video

https://youtu.be/_sFei3iYm0E

Buckwoody Egger · October 7

great work! no root cause! dang. this might fall under the umbrella of “attempted several times and could not recreate the outcome”. i.e. a lightning strike

only other thing i haven’t seen recommended was the ceramic vortex vacuum and reverse siphon test. also known as the sheboygan tornado. not sure if anyone ever made a good adaptor cord to keep it updated because it was 32 pin. nobody posts about that one much online just hear about it some at eggfests.

GrateEggspectations · October 7

Nothing of value to add, really, but I’ll mention that I had a surprising experience some seven or with years back - maybe more. Put a cigar out and rested it in the soil of a fig plant on the front balcony of our prior home. The next day, 30 hours or so later, I’m on the front porch and smell smoke. The cigar had ignited the roots of the small fig plant and had burned slowly beneath the soil all those hours. Scary.

xfire_ATX · October 8

I had this happen when I was using the new Reggulator I bought. After some failed low and slows and the fire re-igniting like yours I realized that the Reggulator top was slightly bent and didnt allow full close off.

Now I only use it with the rain cap for cooks in the rain.

stlcharcoal · October 8

It doesn't take much to keep lump going. I've scooped ash out of my wood stove 36 hrs after the fire was out and have seen tiny red coals in it. I dumped the ash from the egg in a grocery bag 20+ hrs after the cook was over and come back the next day to see a little holes in the bag with char marks. This is why Smokey the Bear is so adamant about making sure your camp fire is truly out.

zaphod · October 8

xfire_ATX said:

I had this happen when I was using the new Reggulator I bought. After some failed low and slows and the fire re-igniting like yours I realized that the Reggulator top was slightly bent and didnt allow full close off.

Now I only use it with the rain cap for cooks in the rain.

i replace the reggulator with a ceramic damper cap - just to be sure, but still it self ignited.

zaphod · October 8

stlcharcoal said:

It doesn't take much to keep lump going. I've scooped ash out of my wood stove 36 hrs after the fire was out and have seen tiny red coals in it. I dumped the ash from the egg in a grocery bag 20+ hrs after the cook was over and come back the next day to see a little holes in the bag with char marks. This is why Smokey the Bear is so adamant about making sure your camp fire is truly out.

yeah, everyone respects Smokey's advice, but no one brings up the fact that he eats park rangers for their hats.

zaphod · October 9

well.... I opened up the dome and left it for 45 min to see what happened.

nothing.

and that's a good thing. the old untouched lump in the basket measure the same temperature as the ambient air. it was dead. so

maybe I didn't close the bottom vent enough
maybe my cleaning out the bottom vent slider groove allows me to close it enough when before I could not
maybe alien beams shot down and lit the old lump in the open dome
maybe it was just one of those times when the old lump had a last ember and I happened to leave the dome open

i'm still looking to get an ash can, but I'm sleeping better now.

DoubleEgger · October 9

I vote for #2

stlcharcoal · October 9

Just keep in mind that it didn't "self-ignite". It just never burned out. It had these three conditions

1 - Fuel (obviously because it is the fuel)
2 - Oxygen (If it didn't have this, it would have been out many many hours prior)
3 - Kindling temp (sometimes incorrectly called "heat", but it was still about 670F).

So it was getting just enough O2 to keeping going and had enough insulation around it to hold temp. As soon as you introduced O2 again, it does what lump does and started burning hot and spreading the fire.

"Self-igniting" can happen with charcoal, but it's usually just with fines outside in huge piles that get really wet and react with the sun. Lump has too much air swirling around it in for that to happen.

Gulfcoastguy · October 9

This reminds me why mine is on concrete at least 5 feet from a building.

zaphod · October 10

DoubleEgger said:

I vote for #2

I really had you pegged for #3. My apologies.

lousubcap · October 10

Valuable lesson across the forum. Great detective work.

Elijah · October 10

I've had similar situations when going to empty ash. The longest I've seen was a hot spot after three days. I wouldn't have noticed if I weren't sorting through the ash.

My egg self ignited the day after a cook

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