Sciencemadness Discussion Board - Pan Rescue: The Case of Burnt Oatmeal

Pan Rescue: The Case of Burnt Oatmeal

AJKOER - 30-11-2019 at 06:32

I experimented with an idea to remove the burnt-on food carbon from a stainless steel pan, which apparently more easily succeeded than I expected!

I wanted to focus on commonly available reagents and avoid, at least, starting with harsh/toxic compounds.

So, I just added 200 ml of dilute 3% household H2O2 and a few teaspoons of sea salt followed by heating to boil. Removed from heat with ongoing stirring/scraping with a metal spoon (for less than 5 minutes). Apparent bubbling (H2O2 decomposition) and an odd smell that had a hint of chlorine. The burnt-on carbon apparently was separating from steel less pan surface.

I suspect some underlying electrochemistry with the highly noble carbon remaining inert, but the surface of the pan undergoing anodic attack. The result was an apparent path for the removal of the burnt-on carbon.

I recommend turning on the vent fan to remove the mild odor and any possible toxic compounds.

Note, even with subsequent scrubbing, still the presence of carbon spots, so not completely a clean/clear result (see pictures).

[Edited on 30-11-2019 by AJKOER]

AJKOER - 30-11-2019 at 06:43

Pictures

[Edited on 30-11-2019 by AJKOER]

AJKOER - 30-11-2019 at 06:51

After the application of a plastic scrubbing pad, still some spots:

[Edited on 30-11-2019 by AJKOER]

[Edited on 30-11-2019 by AJKOER]

AJKOER - 30-11-2019 at 08:02

For those interested on the underlying chemistry, my thoughts on some possible interactions.

First, the creation of some solvated electrons from the presence of Fe, C and O2 in the presence of the NaCl functioning also as an electrolyte.

Then, a possible one-electron reduction of H2O2:

H2O2 + e- --> OH• + OH-

An electrochemical reaction:

Fe + ½ O2 + H+ --> Fe(2+) + OH-

Further with ferrous, H2O2 and O2 :

Fe(+2) = Fe(+3) + e-
O2 + e- = O2•-
O2•- + H+ = HO2• (pKa = 4.88)
HO2• + Fe(+2) + H+ → Fe(+3)+ H2O2
Fe(+2) + H2O2 → Fe(+3) + OH• + OH-

Further possible interaction with excess chloride:

OH• + Cl- = •OHCl-

At pH < 5:

•OHCl- --> OH- + •Cl
•Cl + •Cl --> Cl2 (in small amounts)

From:

Fe --> Fe(ll) + 2 e-
2 [ •Cl + e- = Cl- ]
-------------------------
Fe + 2 •Cl --> FeCl2

and likely more......

Bottom line, an active mix attacking the stainless steel surface facilitating the release of the carbon.

[Edited on 30-11-2019 by AJKOER]

B(a)P - 30-11-2019 at 10:58

This is an amazing post and will definitely help in the justification of my next big lab purchase - chemistry cleans dishes!!

DraconicAcid - 30-11-2019 at 11:36

The carbon burnt to the bottom of the pot isn't pure carbon, but a mixture of carbon and high-carbon-content organic compounds. It's just as likely that the peroxide is breaking down the organic molecules, thus allowing the carbon to be dislodged from the pot.

AJKOER - 30-11-2019 at 13:56

Quote: Originally posted by DraconicAcid

The carbon burnt to the bottom of the pot isn't pure carbon, but a mixture of carbon and high-carbon-content organic compounds. It's just as likely that the peroxide is breaking down the organic molecules, thus allowing the carbon to be dislodged from the pot.

This is a fair comment, but my personal experience in the process suggested to me that there was actually limited dissolving of the burnt-on carbon, and much more of it just entering the solution as a particle suspension. However, I can see how radical activity would be enhanced by the presence of high-carbon-content organic compounds, leading to dissolved organic matter.

From an electrochemistry viewpoint, increasing the surface area of carbon electrode/zone would be expected to increase the rate of anodic attack on the metal pan surface.

So, I admit that there is likely, at least, some degree of a combined process resulting in the surface cleaning.

[Edited on 30-11-2019 by AJKOER]

Vomaturge - 30-11-2019 at 14:48

Quote: Originally posted by AJKOER

Quote: Originally posted by DraconicAcid

If you have a way to estimate the total molarity and oxidation states of iron, nickel (

) chromium (

), etc which are supposedly now in solution, and also measure the concentration of your hydrogen peroxide both BEFORE and AFTER being used to clean the pan, then you'll know for sure how much went into dissolving the stainless steel and how much went into dissolving/re-hydrating the organics so they could be cleared off, along with the more pure carbon which is extremely soft and brittle and needs the other layer to adhere..
I'm not saying such a task is easy, or even that I would be able to do it, but AJKOER claims need extraordinary proof.

If all that hydrogen peroxide was consumed in dissolving stainless steel, and there is now a proportional amount of heavy metal ions in solution, make sure you wash the pan very well the normal way before using it again.

Ubya - 30-11-2019 at 14:55

Quote:

measure the concentration of your hydrogen peroxide both BEFORE and AFTER being used to clean the pan, then you'll know for sure how much went into dissolving the stainless steel and how much went into dissolving/re-hydrating the organics so they could be cleared off, along with the more pure carbon which is extremely soft and brittle and needs the other layer to adhere..

oi oi wait there, that looks like the scientific method, something AJOKER doesn't comprehend. speculation is the key word, why testing an hypothesis if you can speculate as truth?

DraconicAcid - 30-11-2019 at 15:19

Quote: Originally posted by AJKOER

You can't tell me that you can tell by visual inspection how much of the charred mass was carbon and how much of it was black organic material of indefinite composition. Even if only a very minor portion of the charred material dissolves, that will soften the mass and lead it to being suspended particles that are easier to remove.

G-Coupled - 30-11-2019 at 15:52

Has anyone tried Sodium Metasilicate as a cleaner for grease/fat/cooking residues?

It's supposed to form a 'very basic' solution with water which sounds good for the job.

[Edited on 1-12-2019 by G-Coupled]

AJKOER - 30-11-2019 at 17:01

Quote: Originally posted by DraconicAcid

....
You can't tell me that you can tell by visual inspection how much of the charred mass was carbon and how much of it was black organic material of indefinite composition. Even if only a very minor portion of the charred material dissolves, that will soften the mass and lead it to being suspended particles that are easier to remove.

Actually, my relative estimate is that there was more particle mass (as I was scrapping continuously with the metal spoon forming particles) than dissolved organic material present.

As to whether the cleaning is primarily due to loosening as a consequence of surface anodic reaction or from softening of the organic carbon, is, in my opinion, to be opined upon by others who are presented with a cooking accident.

One should also first try just boiling water and scrapping, as that alone may be better than expected. If not, proceed to the household 3% H2O2 (which is acidic) with added sea salt process.

[Edited on 1-12-2019 by AJKOER]

DraconicAcid - 30-11-2019 at 17:04

Did you try it without the salt? Or did you just assume that it had to be there for your imagined free radical pathway?

G-Coupled - 30-11-2019 at 17:05

Piranha Solution - Go Big or Go Home! :cool:

[Edited on 1-12-2019 by G-Coupled]

AJKOER - 30-11-2019 at 17:51

Quote: Originally posted by DraconicAcid

Did you try it without the salt? Or did you just assume that it had to be there for your imagined free radical pathway?

No, I viewed the experiment as a one-shot deal.

For me, the presence of the noble carbon and the stainless steel in an aqueous mix, could in my speculation, benefit from some electrochemistry, which suggests the use of NaCl. With electrons and added H2O2, especially in the presence of Fe, Fenton chemistry is likely adding some radical activity.

A suspension of carbon, by itself, could provide a local surface concentration of electrons. The latter may assist in recycling any transition metal(s) engaged in a fenton reaction. The latter views are advanced and complex by nature, hence my opening electrochemical perspective.

Also, I should cite my prior comments on SM at https://www.sciencemadness.org/whisper/viewthread.php?tid=15... to quote:

"Apparently, burnt vegetables in contact with air and food acids can convert chlorine bleach to ClO3- (in place of IO3- here) and boom, as I noted previously on SM:

"Carbon produced by accidentally burning vegetables is also a source of radicals especially in a pan (of Al or Fe?) with boiling bleach. In fact, there is a report in Bretherick on an explosion occurring by someone trying to clean a pot with burnt vegetables on boiling with NaOCl, and forgetting it was on the stove! An accidentally revealed chlorate route!"

So the unsafe idea of using boiling bleach to attack burnt carbon has been around, likely due to some success. My thought was to substitute safer H2O2 and remove the chlorate explosion part! The incidental creation of chlorate, by the way, suggests to me possible radical activity leading to higher chlorate yield, which would produce an explosion worthy of reporting in the literature.

[Edited on 1-12-2019 by AJKOER]

stoichiometric_steve - 1-12-2019 at 03:51

I think NaOH should have done the job just as well, without attacking the metal too much.

AJKOER - 1-12-2019 at 04:23

Quote: Originally posted by stoichiometric_steve

I think NaOH should have done the job just as well, without attacking the metal too much.

Perhaps as effective but with no possible discoloring?

And then, there is the safety issue (burns).

Leaving a pot loaded with lye laying around in the kitchen does not impress me as wise either.

unionised - 1-12-2019 at 05:26

I'm told that, if you leave the pan outside, the local slugs will eat the burnt on food.
AJKOER will presumably construe this as a free radical reaction.

AJKOER - 1-12-2019 at 07:04

Quote: Originally posted by unionised

I'm told that, if you leave the pan outside, the local slugs will eat the burnt on food.
AJKOER will presumably construe this as a free radical reaction.

Provide a FREE lunch for slugs, what a RADICAL idea resulting in a welcomed REACTION, I suspect.

[Edited on 1-12-2019 by AJKOER]

G-Coupled - 1-12-2019 at 08:54

Quote: Originally posted by AJKOER

Quote: Originally posted by unionised

I'm told that, if you leave the pan outside, the local slugs will eat the burnt on food.
AJKOER will presumably construe this as a free radical reaction.

Provide a FREE lunch for slugs, what a RADICAL idea resulting in a welcomed REACTION, I suspect.

Your username is an anagram of 'A JOKER'.

DraconicAcid - 1-12-2019 at 10:30

Quote: Originally posted by G-Coupled

Your username is an anagram of 'A JOKER'.

I just assumed he had mis-typed it.

AJKOER - 1-12-2019 at 15:01

Jokes aside, there is nothing funny about people putting their roasting pans in the trash because they believe that the pans cannot be cleaned!

Per this site https://cleanmyspace.com/clean-food-off-a-burnt-pot-or-pan/ the provided remedies include boiling water with added NaHCO3 or NaCl and a pre-treatment with vinegar.

A review of my reaction mechanics suggests that adding NaHCO3 at some point may be of assistance due to the formation of the carbonate radical:

•OH + HCO3- = H2O + •CO3-

While the carbonate radical is less powerful than the hydroxyl radical, it has two other advantages. First, it possesses a longer half-life and it is a more selective. In particular, it will attack some compounds (and not others) and can, depending on the organic compound present, actually produce better results!

So, adding Baking Soda could be advantageous if available, although I am not sure if starting with a mix containing NaHCO3 is best as alkaline H2O2 is more readily decomposed.

[Edited on 2-12-2019 by AJKOER]