Baking Steel ...Chemists.. Machinists.. Wiseacres.. is S275 Steel Food Safe?

[adey73]

I want to get my own steel chopped for oven insertion and pizza production.

 

The problem is I want to know if 'mild' steel of structural use is safe for food use.

 

I'd buy in the UK where S275 is easily available and somewhat comparable to the famed A36.

 

BUT EU specs & US specs aren't the same... anyone know probabilities of heavy metals leeching out etc?

Edited March 11, 2017 by adey73 (log)

[paulraphael]

Any steel should be food-safe. You only see exotic alloying elements in higher grade steels, and these are common in knives.

 

A baking steel is also something that's going to be dry and that's going to make relatively brief food contact, and that's going to end up covered with oxidation and probably carbonized oil. There's about zero chance of anything leaching from it—even if there was something bad to leach from it. 

 

FWIW, S275 is just a plain old low-carbon steel. It's got nothing in it but a bit of carbon and manganese. The rest is iron, and the trace impurities that are in every steel. This is the general kind of steel that makes the most sense for what what you're talking about, because it's cheap to buy and cheap to work with.

[adey73]

Thanks Paul.

 

Have you also tried placing a Cordierite stone under the steel to aid thermal recovery?

[paulraphael]

43 minutes ago, adey73 said:

Thanks Paul.

 

Have you also tried placing a Cordierite stone under the steel to aid thermal recovery?

 

Sure haven't. Is that a quote from Star Trek?

[Paul Fink]

4 hours ago, adey73 said:

Thanks Paul.

 

Have you also tried placing a Cordierite stone under the steel to aid thermal recovery?

won't that be redundant?

BTW @paulraphaelis correct. Any steel is food safe.

[IndyRob]

I read the topic title as "Is $275 Steel Food Safe?"

 

I thought "Yeah, but you're paying too much."

[dscheidt]

1 hour ago, Paul Fink said:

won't that be redundant?

BTW @paulraphaelis correct. Any steel is food safe.

Not if there's good conductivity between the ceramic and the steel.  The ceramic has a higher heat capacity (it requires more joules to raise it to a given temperature) than the steel does.  The steel has a higher rate of heat transfer, which is why some people prefer it for some tasks.  When you put someting on the steel to cook, it will transfer heat into the thing that's being cooked, and cool off.  If there's a good conductive transfer between the steel and the stone, the stone will transfer heat into the steel, increasing the amount heat dumped into the food.  When you take the food out, as long as the stone is still hotter than the steel, it will continue to transfer heat into the steel.  That gets the steel up to temperature again faster. 

 

That's the theory.  I doubt it makes much difference, because the bond bewteen the two is so poor. 

[boilsover]

42 minutes ago, dscheidt said:

When you take the food out, as long as the stone is still hotter than the steel, it will continue to transfer heat into the steel.  That gets the steel up to temperature again faster. 

 

That's the theory.  I doubt it makes much difference, because the bond bewteen the two is so poor. 

 

Sort of.  This analysis ignores the effect of infrared radiation that would otherwise heat the bottom of the steel.  The cordierite would basically take the bottom element out of the equation.

 

The "recovery" isn't a giant problem anyway.  If it is, your steel is too thin.  3/8 to 1/2 is about right.  Any thicker and you risk charring the bottom before the toppings are done.

[Paul Fink]

11 hours ago, dscheidt said:

Not if there's good conductivity between the ceramic and the steel.  The ceramic has a higher heat capacity (it requires more joules to raise it to a given temperature) than the steel does.  The steel has a higher rate of heat transfer, which is why some people prefer it for some tasks.  When you put someting on the steel to cook, it will transfer heat into the thing that's being cooked, and cool off.  If there's a good conductive transfer between the steel and the stone, the stone will transfer heat into the steel, increasing the amount heat dumped into the food.  When you take the food out, as long as the stone is still hotter than the steel, it will continue to transfer heat into the steel.  That gets the steel up to temperature again faster. 

 

That's the theory.  I doubt it makes much difference, because the bond between the two is so poor. 

 

 

You have the physics correct. I say its redundant because if the steel is thick it has good heat capacity.

The ceramic has  higher heat capacity per mass but a 1/4" thick hunk of steel is going to be heavier 

than that pizza stone. Think caste iron fry pan.

Edited March 11, 2017 by Paul Fink (log)

[paulraphael]

The downside of adding heat capacity, of course, is the added time and energy to preheat the thing. I have a 1/2" thick steel (weighs around 32 lbs) and it takes my oven at least 75 minutes to preheat it to 550°F. 

 

If you not extra heat capacity (which has been shown to make a big difference when baking multiple pizzas back-to-back, but a very minor difference when baking a single one) the simplest way to get it is with a thicker steel. You maintain the conductivity of the metal all the way through, you have a blackened surface on both sides to absorb radiant heat, and no issues of transferring heat from one piece to another.

 

You can buy steel in whatever thickness you and your oven rack can manage. My advice to most people would be 3/8". That strikes a nice balance. 1/2" is fine if everyone who's going to deal with it has a strong back. If you have big pizza parties and steel-toed shoes, maybe  5/8" would make sense (never heard of anyone using it, though). None of them should be left in the oven full-time. 

Edited March 13, 2017 by paulraphael (log)

[Thanks for the Crepes]

17 hours ago, paulraphael said:

None of them should be left in the oven full-time. 

 

I would like to hear your thoughts on this.

 

[KennethT]

Leaving this mass of steel in your oven is a huge waste of energy and time as it will take much longer to preheat your oven any time you use it.

[paulraphael]

3 hours ago, KennethT said:

Leaving this mass of steel in your oven is a huge waste of energy and time as it will take much longer to preheat your oven any time you use it.

 

This.

[boilsover]

On 3/11/2017 at 5:45 AM, Paul Fink said:

 

 

You have the physics correct.

 

Not really.  Specific heat is usually expressed in tems of mass.  For instance, helium has roughly 6x the specific heat of brick.  Bad physics to suggest that an oven sparged with helium will hold as much heat as the same one lined with brick.

 

My 1/2" pizza steel weighs 42 pounds, and that is significantly more mass than a 1/2" Cordierite tile of the same volume.

Edited March 13, 2017 by boilsover (log)

[Paul Fink]

14 hours ago, boilsover said:

Not really.  Specific heat is usually expressed in tems of mass.  For instance, helium has roughly 6x the specific heat of brick.  Bad physics to suggest that an oven sparged with helium will hold as much heat as the same one lined with brick.

 

My 1/2" pizza steel weighs 42 pounds, and that is significantly more mass than a 1/2" Cordierite tile of the same volume.

 

i think that is what i said or at least what I tried to say. 

[boilsover]

4 hours ago, Paul Fink said:

i think that is what i said or at least what I tried to say. 

 

OK, sorry.  When dscheidt said: "The ceramic has a higher heat capacity (it requires more joules to raise it to a given temperature) than the steel does", you said: "You have the physics correct".    Unless the Cordierite tile is: (a)  6X the thickness of the steel; and (b) thermally bonded to it,  the physics do not work.