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I just got a 100,000 BTU burner for wok cooking. Today when I used it, I got a very thick layer of carbon on the wok (see picture below). Is that normal? Should I remove it? If so, how?

enter image description here

EDIT - FINAL RESULT:

Ok so I took a combination of the advice here.

I used an old metal baby spoon to scrap as much of the loose carbon off as I could. Then I turned the wok burner up to high high heat and burned the crap out of the carbon. A lot of it actually turned liquid and I poured it out. What didnt' turn into liquid, loosened considerably and I was able to, with a hacking/chopping motion of the metal spoon, get all the thick carbon coating off. I was surprised how resilient the seasoning on the wok was, very little of the actual seasoning scraped off. Here's the wok after the burning/hacking with the spoon I used:

enter image description here

Next I used some very coarse sea salt and with my hand I scraped and scraped until the inside was smooth again. Then I wiped some grape seed oil on the wok where the seasoning and come off, and burned it over high heat with the burner. Below is the final result.

enter image description here

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Nice close shot, but almost too minimalist... Now I and James Barrie can't agree if this is the inside or the outside of the wok. Can you throw some light on the matter? –  rumtscho Jun 15 '11 at 7:21
    
@rumtscho: You just gave me a good chuckle, 'cause after you said that I started seeing it that way too! It's the inside of the wok. And in a minute here I will post how I got the carbon off, with pics. –  Richard DesLonde Jun 15 '11 at 7:26
    
This proves my theory that a little elbow grease is worth more than a lot of fancy chemicals, when it comes to carbon –  BobMcGee Jun 16 '11 at 4:02
    
Looks like a normal wok. Probably just too much sugar in your sauce? –  TFD Oct 25 '11 at 6:00
    
@RichardDesLonde Could you provide some more info on your 100,000 BTU burner? That sounds like an amazing cooking tool –  Eric Hu Dec 16 '12 at 2:39

7 Answers 7

up vote 3 down vote accepted

100k BTU sounds like overkill for a single burner unless your wok is HUUUUGE (like, fit to serve a large restaurant). I think that's related to your excessive carbon buildup. A little burned-on crap is normal, but that amount is a sign you're either putting in too much heat, or not keeping enough food moving around in it.

Carbon is... well it rhymes with "witch"... to remove. I've not seen it soluble in anything available outside a chem lab, and there are no easy tricks. Here are the removal methods I've seen:

  1. Scrape it off. This is the standard for serious built-up carbon on pans (particularly ones used as smokers). Use a paint scraper or bench scraper, and steel wool. There are specialty tools for cleaning flat grills which have a flat, very sharp edge that work even better, but in a pinch even a stiff spatula will work. Yes, it's exhausting but it turns out to be surprisingly fast if you can pick a good scraping tool.

  2. Burn it off, using the powerful burner or the self-cleaning cycle on an oven. Be prepared for a lot of smoke. Naturally, you'll have to re-season your wok, but this will remove some of the carbon.

  3. I've HEARD people say they can get carbon off by repeatedly heat-shocking it. This means heating it as hot as possible and then dropping it into ice water. However, they talked about like 30 cycles, and it could render metal more brittle. Might be worth a shot?

Personally I'd either scrape the bejeezus out of it, or just ignore it.

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Thanks Bob. I don't think I'm turning it all the way up to 100k, but you are right it is very hot. And it's funny you should mention a bigger wok, because I am about to buy a big one!!! –  Richard DesLonde Jun 13 '11 at 6:29
    
Even if you're not turning it up all the way, 100k BTU is a LOT of power. That's appropriate for a restaurant, heating a 80+ quart stockpot. If you're getting that level of carbon buildup, you're definitely using it too high. –  BobMcGee Jun 13 '11 at 17:12
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Actually, gun cleaning solvent can do a number on carbon, if you're able to buy it where you live. Probably easier to get access to than a chem lab. –  Aaronut Jun 13 '11 at 19:06
    
@Aaronut: Greasy and oily residues, or burnt-on oil are not the same as straight-up charcoal. There are plenty of solvents that remove the residues as long as they are still oil-based and not pure carbon. Degreaser, gun cleaner, organic solvents... even a good soak in soap and water: all of these work there. Once it's converted from hydrocarbons to carbon black, you're buggered. –  BobMcGee Jun 13 '11 at 23:25
    
Yes, I know, but many of the gun cleaners are specifically designed for carbon/charcoal build-up, which is a common problem with guns. There's even a review for the product hobodave links to which says that it works well on carbon. Carbon is not very chemically active but it's not completely inert either. –  Aaronut Jun 14 '11 at 0:44

If the other methods fail, you should be able to get your wok to gleam as new. For this, you'll need to use a strong lye bath (sodium hydroxide). Leave it a day or two in a small glass or plastic tub (if plastic, brush a spot with lye first to make sure it doesn't dissolve), then remove and clean with lots of water. Both carbon and seasoning will be removed.

Be aware that this is a drastic solution, usually saved for when a pan has rusted below an improper seasoning. The lye doesn't have toxic fumes or similar, but if it comes in contact with your skin, it will cause serious chemical burns. Take extensive precautions (gloves overlapped by sleeves, safety glasses or at least ski glasses which cover from the side too). If there is a child or pet in the household, don't do it, unless you are able to lock the full tub somewhere (e.g. a garden shed).

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Lye is strong stuff, and will strip fats, grease, and burned-on food... but I don't think it'll do anything for straight-up carbon. Pretty much nothing does, including the industrial degreasers, oven cleaners, and bleach that I've tried. As far as I know, you have to go up to industrial solvents such as benzene, toulene, and carbon disulfide to even start dissolving it. –  BobMcGee Jun 13 '11 at 17:06
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@BobMcGee the lye doesn't have to dissolve the carbon. It dissolves the seasoning underneath the carbon, leaving pure shiny metal. (And unlike a strong acid, it doesn't attack the metal itself). The carbon can dissolve or come off in rags. But the pan is clean and ready for a new seasoning. –  rumtscho Jun 14 '11 at 11:29
    
great for general problems, but the carbon looks like it is on the outside in the pic ... –  James Barrie Jun 15 '11 at 1:33
    
@James Barrie First, I usually have no problem with seeing both parts of a reversible figure, but I can't get a stable picture of this thing as the "outside" of a wok (I almost get it, but not stable). That would be some very weird lighting. Second, even if it is on the outside, I think that it will work, as the lye eats away any impurities, (maybe even the black iron oxide) not only seasoning. –  rumtscho Jun 15 '11 at 7:18

I bought a metal brush for a drill and used that to clean of carbon. I also put oil on a cast iron and burn it off to season it. It will prevent this type of carbon buildup in the future. Then use coarse salt and a rag to sand down the pan or wok after every use followed by a coating of oil. If the oil is giving time to burn off then it will stay clean and nice. Never, never use soap on any type of cast iron.

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Now let's get this right - if the burner is set up right, it shouldn't leave the soot on the wok, so the burner needs to be set leaner = more air, less gas.

Now, not much dissolves carbon. Sulphuric acid will do it, but it also tends to dissolve woks!

Solutions: adjust the burner to get more air in the flame - not a hint of yellow or sparkle, just blue flame.

For the wok - leave it out in the yard and let nature clean it. Getting a little rust off is a breeze compared to carbon deposits. If the carbon is a little tarry, you can sometimes get a lot off by wiping with corn oil, then cleaning that mess off with neat engine cleaner.

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Not sure how to adjust the air in the flame. How is that done? This is just a simple burner with an "AmeriGas" propane tank. –  Richard DesLonde Jun 15 '11 at 7:45

commercial kitchen carbon remover. No scrubbing no scraping, just soak it in the Fog Tank. http://tinyurl.com/3f23t3o

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I'm gonna guess the number of home users with a Fog Tank is pretty low... –  rfusca Oct 24 '11 at 4:27

To remove carbon you can use sodium hydroxide (caustic soda) however it must be a very strong (high molarity) and constantly boiling. I've done it using an old sink and portable gas ring heater but do note this is very dangerous and I accept no liability for people trying this.

PS I'm an industrial chemist.

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I burnt some stuff onto the surface of my wok and it was solid like a rock. I scrubbed it off by using a piece of "Wet and Dry" sand paper, about 400 grit. I wet the paper, put about a cupful of warm water in the wok plus a few drops of dish detergent. The Wet and Dry eats the hard carbon off like a starving horse eats grass and the detergent cuts the surface tension of the water. You can sand it right down to the original surface with no trouble. Be careful that you don't sand into the shiny metal. You can continue sanding with 1000 grit or finer and it will polish the steel surface beautifully. When finished to your requirements, wash with hot water and immediately dry and oil the wok. Season the wok again as soon as possible as the clean polished surface will begin to rust quickly. I clean my wok and all other burnt fry pans in this way and the results are wonderful. It is also very quick to do. My 18" wok took only 15 minutes to be returned like new ready for seasoning.

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