Sunday, August 7, 2011

The science and technology of wok

I have a few large woks and frying pans, all ruined, by wife.  The importance of wok is that, it could cure anorexia or the early development of it.  My small kid would eat everything that comes out of the wok, but will make a lot of diplomatic efforts in order not to eat other things.

It was time to replace the wok, actually deep frying pan.  It was always time.  With all the negative news about non-stick pans, our well scratched non-stick frying pan seemed to be a health hazard.

I went to Target with all the beautiful cook wares.  It was a mistake.  I would think that they would have come up with a safe non-stick now.  So I brought a non-stick frying pan that seemed to have an indestructible non-stick surface.  They always claim that on infomercials.

The non-stick surface didn't come off this time.  Perhaps wife didn't use a steel spatula to scrub on the food stain.  But food stain did get on the side non-stick surface.  We use intense heat, otherwise it wouldn't be stir fry.

That didn't bother me a bit, except that when the pan is heated, small brown bubbles will come out on the side like boiling.  It's the same whenever we wash it, and then heat it again.  I'm not worried if that's food residue like soy source, that we used a lot.  But I'm worried about other chemicals.

So this IS time to get another wok.  From my research last time, I know it have to be a case iron wok.  (Wrong)  Just that Target and most cook ware shops don't have it, at least not in the form of a wok or practical frying pan.

A wok with a flat base is basically a deep frying pan.  A round normal wok is perfect if you have gas (gasoline, propane).  For electric and induction you need a flat base.  But a flat base wok is not really a wok.   And in the western world, you need a wok ring as a stand for the round bottomed wok.

You choice of material is cast iron and carbon steel (and stainless steel).  You don't want any coating on the inside or the outside.  They don't last, can't stand intense heat, or they just want more of your money.

I made the silly mistake that cast iron is iron, and carbon steel is steel.  I have enough stainless cookware.  Each and every one have food stains on it.  Wife prefer to fry in pots without the oil splashing around.  The good thing about stainless steel is that even with a lot of scrub marks, the outside and inside looks decent, except for the spots with food stain on it.  You can remove stains if you try hard enough, and there are chemicals to do it.

Obviously stainless steel is not a replacement for non-stick.  I'm sure cast iron is the nearest thing.

Basically everything is steel or everything is carbon steel.  The least refined steel is cast iron, iron with carbon content > 2%.  More refined is carbon steel with less carbon content.  Stainless steel is steel with chrome added so it will not rust.  The lesser the amount of carbon, the harder is the steel.

The confusion with cast iron is that traditional western cast iron cook ware is very different from traditional Chinese cast iron wok.  Western cast iron is thick, rough surface and I bet very non-stick.  Chinese cast iron wok is not a lot different from a carbon steel wok in appearance and weight.

My explanation can be that western cast iron has higher carbon content, so they are more brittle and hence it has to be thicker.  And the high carbon content cast iron is suitable to use sand mold to cast the shape of a frying pan or wok.  Chinese cast iron wok has lower carbon content, hence stronger.  I think they are made like pressing on a piece of red hot iron into the shape of a wok.

You can dismiss western cast iron cookware if you want Chinese style stir fry.  They are good for what they are designed to cook traditionally.  And I bet they are really non stick, because it doesn't matter if there is any stain on it or not.  It heat up slow and is heavy.

So basically it's steel with varying carbon content, and the high carbon content "cast iron" are at the cheaper end it cost to reduce carbon content.

"Carbon steel" heat up faster, harder and in general thinner, lighter.

Basically that's all academic.  It does not make that much difference if you fry on occasion or even daily, as opposed to in a Chinese restaurant.  A piece of iron with 2% or 1% carbon do not make that much of a difference in a family setting.

A a piece of machine made piece of iron cannot be fragile.  If you do not use your wok as a fighting shield, a cast iron wok is fine, which could still last a lifetime, what Chinese expects of their wok.  And it's only $10.

Stronger carbon steel can be made thinner.  It heats up faster and weight less.  The weight is important as the smallest wok is some 13" diameter up to 16 or larger in restaurants.  It will be your largest piece of cookware so you decide what weight you can deal with, on and off the stove, hanging it up, putting it in the cabinet, hand washing, etc.

For carbon steel I would go for those hand hammered.  I bet the purpose is to make it thinner.  It only cost a little extra.  They have steel and they have labor.  You just can't compete.

Now the only other consideration is seasoning.  Before use, you have to oil it and burn it to give it a protecting and non stick surface.  Many people seemed to worry about it, doing it wrong.

In iron age terms, you are adding food stain to a weapon, to use in a kitchen when you are not fighting.  You just can't do it wrong.

I suppose higher carbon content cast iron have a rougher surface and holds food stain better.  Food stains come off in stainless steel pots, so people are worrying that "seasoning" come off easier in carbon steel.  That's laughable.  No body worries about food stain coming off too easy.  You can always reapply.  But in normal use food will always stain your wok.

The worry is that food stain will become too thick, and come off in blocks, making the wok surface uneven. But you can deal with it one way or another, or all by itself.

Please don't say that "I need to toss it" unless you are a Chinese cook, or intended to be.  It only happens, perhaps, in kitchens in Chinese restaurants.  It's a hazard to do it in your own kitchen.  So it doesn't need to be that light, and don't need a long and strong handle.

The most practical handle is the small loop ones holding securing with two rivets.  That's indestructible and most space saving.  If you want to move it when hot, you can just use two wet washing cloth.  Don't move it while cooking, and you don't need to.  A long handle may break at the welding point, and wooden handles are silly idea, unless you can replace it.  Though the whole thing is rather cheap - a piece of iron.

If you have rust, that means your food stain is not good enough.  You can just scrub off the rust and food will find it's way to stain it.  The wok is iron and rust is sort of iron oxide, stable compounds what wouldn't do anything to your body.  These will just pass out straight away.  You won't get iron supplement either - they have to be in soluble ion form.

Now they are teaching home cooks to stain their cook ware with food, and how to make them stay.  And not to use soap to wash woks.  How lovely.  But wife and many home makers have obsession with removing stains.  That will education them good.

Surprisingly, even Chinese supermarkets don't sell authentic woks as used in Chinese homes for ages.  Perhaps they are too cheap, from $10 for cast iron to $20 for hand hammered carbon steel with a steel tossing handle.  You can find the Wok Shop selling woks online for at least several years.  There's no other competition.  They are in San Francisco China town.  So you are mostly paying for the postage.  If you are on a road trip there, this is your gift idea.

No comments: