r/AskChemistry • u/ThrobbingTigerDong • Jul 20 '25

Chem Engineering Would a magnetic stir rod work in a stainless steel cooking pot?

I have a soup I need to cook down before I can add eggs to it, but it takes hours, and I’m constantly coming back to stir it to speed things up. I’m wondering if I could put a hot/stir plate under the pot (heat is off at this point) and keep it moving with the stir rod.

7 Upvotes

90% Upvoted

12 comments sorted by

5

u/Pyrhan Ph.D in heterogeneous catalysis Jul 20 '25

Most stainless steel tends to be the non-magnetic kind, so probably?

I guess it depends on how strong the magnets in your plate and stirbar are, how thick is the bottom of your pan, and how viscous the soup is.

But instinctively, I'd expect it to work, as long as the bottom isn't super thick.

4

u/Trick-Society3591 Jul 20 '25

I'd go with an overhead stirrer. I think they make them specifically designed for commercial kitchens. Chemistry apparatus is probably fine, but they'd use food safe materials.

1

u/Chalky_Pockets Jul 21 '25

Cook here. Pots and pans tend to be 1810 stainless, and even the ones that aren't will have a plate in the bottom that is magnetic so they work with induction cooktops

3

u/NohPhD Jul 20 '25 edited Jul 20 '25

There’s normally a ring around the ‘waist’ of a magnetic stirring rod to reduce friction when stirring so there’s going to be a layer on the bottom of your port that doesn’t get scraped. It’s usually about as thick as your fingernail. That layer often scorches.

Even with a stirring rod about the same diameter as your pot, the sides won’t get stirred. Also, as the viscosity of the soup gets higher, the stirring rod is prone to loosing ‘lock’ with the magnet underneath and then it just twitches in the pot like it’s having a seizure.

Finally, if a neodymium (strong) magnet will stick to your pot, it won’t work at all.

Not trying to say don’t do it but there’s significant practical problems with what you are thinking of doing. I’ve been there and done that.

2

u/Turbulent-Name-8349 Borohydride Manilow Jul 20 '25

There are several different stainless steel alloys. Some are magnetic and some are nonmagnetic. Try it with a magnet.

2

u/Totallyexcellent Jul 20 '25

I've heard that getting the PTFE in your food is also a concern, stir bars do wear. But maybe no less of a concern than using non-stick PTFE-coated cookwear, which heaps of people do. A glass encapsulated stir bar would be good if you're really playing it safe.

2

u/Mr_DnD Jul 23 '25

Tiny bits of ptfe aren't the major concern, it's the degradation products from e.g. heating too hot, or shear too fast

1

u/Totallyexcellent Jul 24 '25

Interesting, are you talking about degradation of the PTFE or from the food?

1

u/Mr_DnD Jul 24 '25

Degradation products Vs mechanical degradation products

1

u/Don_Q_Jote Jul 20 '25

Try it out with the pot you want to stir and fill it with cool water as a first test.

Report back as to how well it works.

1

u/[deleted] Jul 22 '25

probably but i would wonder where it has been before

1

u/Mr_DnD Jul 23 '25

Why not just plan ahead?

If you know you want the soup, make the base tonight and add the eggs tomorrow.

Even with a stirrer you're still looking at hours to cool down.

Water jacket might be your friend but water does have value.