Sciencemadness Discussion Board

Metal Pot on Ceramic Hotplate

Abromination - 14-8-2019 at 21:16

Well, my internet crashed and I lost my damn post so Ill keep this short.

My hotplate stirrer says not to use metal pots on its ceramic top when using an oil/water bath. Is this something to be considered an actual hazard? I can get the idea behind it but I dont know if it will actually ruin the hotplate. Ive seen many others do it with similar corning hotplates, but I’m not sure.
Thanks.

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gussing;

Sulaiman - 14-8-2019 at 21:47

maybe it is to avoid people putting ferromagnetic pots that would prevent magnetic stirring ?

any metal pot, even Al, Cu etc. will cause an extra load on the stirrer motor due to eddy currents/ Lenz's law.

Abromination - 15-8-2019 at 00:02

I think the manual said something about overheating of the ceramic top. Ill find it in the morning, I’m too damn tired tonight. Luckily, if the motor malfunctions, it will actually automatically shut itself off to prevent damage of the stirring function. It also warns against coating the ceramic top in aluminium foil. I suppose they are concerned about the top cracking under heat stress.

Ubya - 15-8-2019 at 00:58

metal should conduct heat faster from the plate, i can't understand the connection with a overheating problem

draculic acid69 - 15-8-2019 at 08:28

Is the actual plate made of ceramic or is it just an aluminium plate with some sort of ceramic coating sprayed on it?

Abromination - 15-8-2019 at 08:52

Quote: Originally posted by draculic acid69  
Is the actual plate made of ceramic or is it just an aluminium plate with some sort of ceramic coating sprayed on it?

It is aluminum coated ceramic, similar to most other ceramic topped hotplates including all of the corning brand hotplates I have used. I should also add that I have seen the same warning on corning hotplates about cracking of the ceramic top while using metal pots for baths.

WGTR - 15-8-2019 at 18:44

It’s because the metal container will not be flat enough to make full contact with the hot plate over its entire surface. The parts that contact the hot plate directly can wick heat away from the ceramic surface quickly, causing heat stress across the ceramic surface, and possible cracking.

wg48temp9 - 16-8-2019 at 02:31

Quote: Originally posted by WGTR  
It’s because the metal container will not be flat enough to make full contact with the hot plate over its entire surface. The parts that contact the hot plate directly can wick heat away from the ceramic surface quickly, causing heat stress across the ceramic surface, and possible cracking.


That does not make sense to me as all my SS pots are much flatter than my glass beakers and glass FB flasks.

Perhaps its reflectivity of the SS is the problem.

draculic acid69 - 16-8-2019 at 02:44

Quote: Originally posted by Abromination  
Quote: Originally posted by draculic acid69  
Is the actual plate made of ceramic or is it just an aluminium plate with some sort of ceramic coating sprayed on it?

It is aluminum coated ceramic, similar to most other ceramic topped hotplates including all of the corning brand hotplates I have used. I should also add that I have seen the same warning on corning hotplates about cracking of the ceramic top while using metal pots for baths.


You mean aluminium coated WITH ceramic right?
Not just that but how would a aluminium plate crack? Has anyone ever had one crack?

Abromination - 16-8-2019 at 09:43

Quote: Originally posted by draculic acid69  
Quote: Originally posted by Abromination  
Quote: Originally posted by draculic acid69  
Is the actual plate made of ceramic or is it just an aluminium plate with some sort of ceramic coating sprayed on it?

It is aluminum coated ceramic, similar to most other ceramic topped hotplates including all of the corning brand hotplates I have used. I should also add that I have seen the same warning on corning hotplates about cracking of the ceramic top while using metal pots for baths.


You mean aluminium coated WITH ceramic right?
Not just that but how would a aluminium plate crack? Has anyone ever had one crack?

I meant aluminum coated with ceramic. I also found that it is not aluminum but stainless steel. And it would be the ceramic that would crack, not the thin metal sheet underneath. I found the manual and cracking in the manner WGBT described is what they were concerned about. My question of whether or not metal should be totally avoided has still not been answered. Like I said, I have seen many people use metal pots on similar hotplates with similar warnings from brands such as Corning yet I have never heard of this causing damage to the hotplate surface.

Pumukli - 16-8-2019 at 10:50

WGTR's explanation does make sens I think!

Irregularities in glass beakers and other glassware is not a problem, because glass is a bad thermal conductor (compared to metals) and can't syphon the heat away from spots on the ceramic to such an extent as the bottom of a metal pot could.
Especially if that pot was just removed from the fridge and contains a big chunk of ice...

Or a cold oil/water bath to start to heat it up.