Had a bit of a misshap - whats melted?

[applor]

Hi all,

Been a while since I've posted here, just been using the oven

I read recently that after using your oven and the fire has gone out you can put your whole wood pieces in the oven to dry them out and make them easy to split and fire later.

I have since done it once before, no problems.
The next time I went to do it however, I think I put the wood in when the fire was too hot.
Despite having the door sealed with no airflow, there must have been enough air getting in for the wood to combust and it has burnt through to charcoal, without being any real fire.

I only know because I went to split the wood a few weeks after and found my door was a bit stuck to the deck and had bubbled on the inside.
In addition, when I went to remove the wood I found that despite being whole, it was actually just charcoal.

Whatever has happened, there is now a ridge of some substance along the deck that I need to remove. I will also need to do something about the door.
The door was just plain steel, though I guess it must have been painted and it is in fact the paint that has melted off and down onto the deck?

Take a look at the photos and let me know what you think:

[applor]

[texman]

looks like just the paint failed. How hot was the oven and what kind of paint?

[Gulf]

Take a wire brush and see how much of the paint residual can be removed from the door. If any is left use a propane torch to remove the rest. After that you can reseal the door with vegetable oil. Scrape as much of the paint residual as you can from the floor. You may want to refire the oven to get the floor up to temp. Then take the same propane torch and burn the rest off.

Let your oven fall below 350F before placing wood in to dry unless you are actually wanting to make lump charcoal. It is a good thing that you waited some time before opening the door or you may have lost your eyebrows from a backdraft flare up .

[applor]

No idea on the paint, it came painted as part of the kit. So definitely paint then.

Thanks for the advice Gulf. I have an angle grinder too so I can grind the door clean as well. More concerning is the paint on the deck.
I will scrape off what I can and try to burn the rest off as you suggested.

Yeah I had no plans to open the oven again Made some good lump charcoal that's for sure. Any use for it other than garden fertilizer?

I still need to build myself an insulated door so it might pay to do that when I clean the door up - If I get around to it:/

[JRPizza]

My door is unpainted steel, but I have gotten similar deposits when I use the door to seal the oven when there is still a fire in it (creosote maybe?). I'll try to post a picture of the deposits, but right now the door is keeping the oven hot . If you know the door was painted then paint is the probable culprit. If the door was bare I'd suspect some sort of combustion byproduct.

[Gulf]

..................Made some good lump charcoal that's for sure. Any use for it other than garden fertilizer?...............

For anything that you would use briquettes (heat beads) and more. It's what everyone used before Henry Ford started adding anthracite coal and special binders to his trashie wooden pallets that were left over from his auto production line.(That is what charcoal briqettes are made from) Lump burns a lot cleaner than briquettes. Imo that translates to a better taiste when used for grilling. It can be used in your oven to help get a hot coal bed started sooner which translates to less smoke on startup of the oven. Lump can be used to get a few more degrees in an oven that is on the decline in temp. It is becoming more and more poular with backyard grillers. I'm one of them.

The white to grayish ash left over from the oven is actually what is good for the garden. That ash has other uses as well. Hardwood ash contains potasium. It has been used to make potasium hydroxide (lye) for soap making, hog scalding and many other uses. Hardwood ash has even been used as a levin for bread making.

Anything black left over from the oven is wasted fuel. I've used different methods to recover the lump from ash depending wether the oven was hot or cold. I built a scoop from expanded metal which helps me separate the lump from ash in a hot or cold oven.

[SableSprings]

...The next time I went to do it however, I think I put the wood in when the fire was too hot.
Despite having the door sealed with no airflow, there must have been enough air getting in for the wood to combust and it has burnt through to charcoal, without being any real fire.

I only know because I went to split the wood a few weeks after and found my door was a bit stuck to the deck and had bubbled on the inside.
In addition, when I went to remove the wood I found that despite being whole, it was actually just charcoal.

Whatever has happened, there is now a ridge of some substance along the deck that I need to remove. I will also need to do something about the door.
The door was just plain steel, though I guess it must have been painted and it is in fact the paint that has melted off and down onto the deck?...

That buildup on the door and along the deck is basically creosote. When you put the wood in the "too hot" oven and closed the door you actually caused a potentially dangerous situation. Combustible gases are being created from the heat, but without enough oxygen they will deposit as flaky, gummy, and hard "tar" layers. If you open an oven that's full of this combustible, hot gas - it will ignite explosively. Firemen call this a back-flash situation, pottery people call it a reduction fire. Useful technique in pottery & kiln work, but dangerous for firemen in structure fires. In the structure fire, a closed room heats up (closed oven with wood), air is suddenly sucked in (when door is opened), the gases suddenly ignite, and then basically explode out.

If you use the wood drying technique (as many of us in wetter climes do), IMHO you don't want to put the wood into the oven if it's above 250F or so (I wait for a cooler oven than Gulf advised above because after a couple of back-draft fires I'm a little gun shy ). Also, you always want to leave the door open a bit for the moisture to escape. When I use a warm oven to dry wood, I usually leave the door cracked open until the oven (and wood) have cooled down completely before closing up. If you do accidentally put your wood in the oven while it's a bit too hot then close the door just a little too tightly and then later notice white smoke kind of puffing out your chimney...you probably have a reduction fire situation. Leave it to cool down! If you open the door just a little bit more (cause you can't resist), brace yourself and the door because opening it very likely will produce a pretty good wummmf and push the door out when those hot gases ignite. I've had this happen a couple of times and frankly it is scary as hell

I get some of those same kind of deposits around the edges of my stainless steel fire door when I make my overnight, damped down "pre-heating" fire. I always make sure before I go to bed that I've left enough of an opening to keep a consistent fire going (and not choke the fire ). As Gulf advised, the wire brush and propane torch/scraper will clean most of the creosote deposits off your door and deck. Relax and think of this as another great lesson in using the WFO.

[applor]

Thanks for the replies all,

I will say I am very aware of the risks of a backdraft and would never have opened the door in that situation - this discovery is well over a month since I used the oven.
My mistake was putting the wood into the oven too soon, so I won't do that again.

The information from Gulf about charcoal and ash has been informative.

[Gulf]

Thanks Applor,

I'm glad it was not paint on the door. I misread the op. Completely dry wood will self combust roughly @ 450F. I give a 100 degree safety margin. Mike gives a 200 degree safety margin. Even better. I'm going to clarify my recomendation for safety purposes. A clean oven which has been raked out will be ok to add wood @ 350F. I can't say the same for an oven that still has ash inside. There can be smoldering embers hiding under all that ash and char. Ash can act as an insulation, which may prevent the temp gun from finding those hot spots.

Also, for the lump charcoal: Search for "caveman style steaks" .

[RCP]

You made charcoal, no big deal. Use steel wool to clean off the loose paint and buy a can of high temp fireplace paint.