Copper vs Aluminum - CenturyLife Boiling Speed Test

In Franz’s boiling speed tests he found comparing copper disc bottom (Demeyere) to aluminum disc bottom (Sitram Profiserie) to be nearly identical in boiling speed.

These results seem to be counterintuitive, considering we know copper is faster to heat up and twice as conductive as aluminum.


  1. What accounts for the similar results in boiling speed?
  2. Would boiling speeds be any different in a larger size pot, e.g. 28 cm?

Well, there are many factors to this. Heat conductivity is only one part of a large picture. The thermal conductivity of glass is 500 times less than that of copper, but you don’t expect the boiling time to be different by 500 fold.

If we take a step back, there are at least three steps. a) The energy transfer from gas flame to the bottom of the pot. b) the energy transfer from the bottom surface of the pot to the top surface of the pot (basically, your aluminum and copper disc). c) the energy transfer to the water.

So really, what you pointed out is the second part and it is a small part compared to the other two.

In addition, don’t forget that we are talking about copper disc and aluminum disc sandwiched by stainless steel. With the stainless steel there, a lot of things are much closer.

Citing some conductivity numbers (W/m * K)

Aluminum 205
Copper 385
Steel 50.2

So the thermal resistivity numbers are:

Aluminum 0.0049
Copper 0.0026
Steel 0.020

As you noticed, steel’s resistivity is much higher than those of aluminum and copper. So when you combined them together (like layers of steel and aluminum or layers of steel and copper), then the steel is likely to play a big role in thermal resistance. Or in other words, your conductivity in that cladded material can be largely influenced by the steel.

Although not a surprise, I found this interesting:

QUOTE: At 67.2F water and 69.2F air temperature, the copper + copper lid boiled in 16 minutes. The copper + stainless lid boiled in 15 minutes. Not bad when the only difference was switching from copper to stainless lid.

Hi Seitan,

I would have used a different volume of water, a different heating source, and a different dependent variable, time to running boil or specific temperature. Why?

I would have wanted to mirror the real world of cooking much more closely. As someone who steams a great deal, with and without pressure, I haven’t used more than a quart of water–much less with my poacher. The electric heating element chosen seems not to be a reliable source of continuous energy–gas at a specific btu per burner would be much better. The dependent variable should be time to boiling and not temperature change along the way (with indicators for statistical significant differences)–the nonlinear change measured and graphed masks the final conversion time to boil. If it were to be temperature change, it should be time to a specific temperature target with the appropriate lid. Statistical tests should measure for significant differences at the .01 level.

I suspect that tests that more closely represent typical real world cooking tasks would give us more intuitive results.


The other factor I would add is that small volumes of water and small amounts of metal are going to produce very very small, probably immaterial differences, or at least differences that are difficult to perceive.

Add in you point about the amount of steel neutralising the influence of the aluminium or copper and it can be seen the different heating attributes of pans are quite insignificant…putting the pan lid on probably makes the most difference.

That said, I have recently started to use an induction hob and can’t believe how fast that boils water compared to standard electrical or gas hobs…it is really a dramatic difference.

Hi Ray, thanks.
I think Franz did do time-to-boiling, unless I’ve misunderstood the graph. Wouldn’t the end point on the graph be boiling time?

I have done my own boiling speed tests, one such test with a 1.5 liter Cuisinart Multiclad Pro sauce pan against a 1.5 liter Demeyere Atlantis (I borrowed). My methodology was starting water temp the same, 1 liter of water, and using the same burner on the stove. I timed each pot to 200 degrees F (which where I live is a rolling boil). The Atlantis pot beat the Multiclad by almost exactly one minute. I was hoping to run the same test with larger pots to see if there would be an increased effect, but I haven’t been able to get hold of a large Atlantis pot.

As an aside, what I discovered, after doing a whole bunch of tests with different cookware, was that the height of water in the pan can have an enormous effect on speed. For instance, the Atlantis 1.5 liter saucepan is shaped lower and wider than the 1.5 liter Multiclad saucepan, which is a little taller and narrower. (and small All-Clad saucepans, for example, are shaped even taller). In my methodology, I also measured the height of the volume of water inside each pot. With 1 liter of water in a 1.5 liter Multiclad saucepan, the measured height was 2-5/8". The boiling speed at this height of water was 7 min. 40 seconds. When I reduced the height to 2", the boiling speed was 5 min. 2 sec. Just a half an inch difference in water height can mean a 2 minute reduction in boiling time. The Atlantis pot when filled with 1 liter of water, also measured 2 inches high. I then realized that the sauce pan shape may be having an effect on the timed speed (and thus throwing off results) when trying to compare pots with an otherwise equal capacity, even when filled with an equal volume of water.

What I don’t get about Franz’s results (and I have no reason to doubt or question them) is that the pots he used were the same shape. The Profiserie was also a lot thicker than the Atlantis.

Hi Seitan,

Franz did “time at temperature point”, not “time to criterion.” The fluctuation near the criterion can introduce variability into the readings–which one tests for by repeating exactly the same measurement quite a few times and then correlating the measurements. There are many design requirements like this for a serious study that make interpreting his findings virtually impossible.

I have informally given myself about 3 minutes to bring water to a boil in various straight sided containers with about one inch or water, 6 to 8 inches diameter. I have tri ply cladded, ECI cast iron, enameled SS, and 2 tri ply encapsulated (one is my Demeyere poacher). I also have three conical saucier pans, most recently a 2 qt. copper core. The conical ones are faster, and the copper core is the fastest. I doubt that any of them take more than 5 minutes to running boil.


I don’t think its the height of the water, the height simply correlates with the diameter of the pot and there is a relationship between diameter and efficiency of heat transfer from a stove top.

A larger diameter captures more of the heat with less heat lost around the the edge of the pan so is more simply efficient. Even if a flame isn’t licking around the side there is significant heat loss. An electric hob, if the element is fully covered by the pot may see less heat loss and thus more efficient heat transfer.

My mother, who was brought up in more frugal times, always stressed you needed to use the right burner with a correct pan to avoid wasting heat. and never have a gas flame extending beyond the width of a pan - that just wastes heat and the pan is slower to heat.

Ray: What is ‘time to criterion’?

Phil: the diameter of the MultiClad in which I did the water height test remained the same, since it was the same pot. A half inch less water increased boiling speed by two minutes. I placed both the MultiClad and the Atlantis 1.5 liter pans on a 6" electric coil burner. Both pans covered the burner.

Hi Seitan,

For me, “time to criterion” would be time that started with the water in place at the push of a button on my Mirage Pro, and end when I saw a certain rolling boil pattern in the water of the pan. I would never measure temperature at all.

If there is less water in the same pan it will boil faster as there is less water to heat…its nothing to do with the height of the water.

Regarding the burner: it depends on how efficient the coverage is of the burner and the contact. Most electric coils have space around them which allows heat to dissipate (so approx 80% efficient). A smaller diameter pan allows for more heat to escape even if the pan covers the ring so less efficient than a bigger pan.

A glass ceramic top wold be more efficient but even these have heat loss - that’s why they get hot. Induction has no heat loss as its the pan that heats not an element - that is one reason they boil water so fast as there is no heat transfer loss.

Phil, I see what you mean. That makes sense. It’s just that I tried testing other sauce pans of the same low profile shape (Lagostina, Cuisinart Professional Blue) and they both were faster to boil than the taller MultiClad. They were disc base, so maybe that was the deciding factor.

Ray, if you choose the end time as being when you see water start to boil, isn’t that a little subjective? Why wouldn’t reaching a certain temperature point be more accurate?

Hi seitan,

As a pilot test, try it both ways.

Whatever criterion is chosen, reliability must be established. As subjective as it seems, I’d bet that recognizing a running boil is more reliable than a temperature measure, but that’s just until reliability data is gathered. If temperature is a better criterion, the correlation will be higher.


If speed is the sole criteria there is nothing faster than a big microwave tube and a pyrex container.

It would be much more efficient at transferring energy directly to the liquid than any metal pot on a burner.

Hi VikingKaj,

Is this a philosophical belief, or have you made measurements?

What specific comparisons have you made between microwave and induction? What’s the time difference?


Microwaves transfer the energy to the water molecules directly.

With an induction cooktop the energy has to go through an additional barrier, the cooking vessel.

So microwaves are going to transfer a given volume of energy faster with less loss.

The speed, of course, depends on the size of your burner:

Different variables with the MW. The waves only excite the molecules within a given distance of the wall Usually about 1.5"), not necessarily equally from all sides, and you must assess the radiolucency of the vessel. I’m sure there are more.

Hi Ray,

“Whatever criterion is chosen, reliability must be established. As subjective as it seems, I’d bet that recognizing a running boil is more reliable than a temperature measure,”

A boil is a process. At what point in the process do you arbitrarily consider water to have ‘reached a boil’? 500 bubbles?, 1000 bubbles.? You need a precise marker to make it reliable. A specific temperature goal, on the other hand, is a precise mark, and a reliable one, precisely because it’s exact.

Hi, Seitan:

There are many variables at work here. But from a macro perspective, thinness is probably a speed boost to boiling water fast. If you could make a copper pan thin enough to allow its skin depth compatibility in the 22-24kHz induction frequency range, such a pan would likely beat both pans Franz tested. I remember Politeness and another Chowhound poster saying their fastest boils came in a thin SS mixing bowl and an enameled steel canner.

One way of looking at it is that a thick pan has less heat moderating effect to gas or electric than does a thicker pan–more of the 3500F gas flame is closer to the pan/water interface. Water is not the greatest conductor, but it is so thin that convection currents are easy to start; these currents are a more effective means of heating the water as a whole than is pushing heat up the sides or across a base. Basically, if you have a hot enough spot and even fair heat transfer, the convection currents will work about the same with all pans.

There are probably 10-20 other factors that might explain Franz’s particular result, but other than evaporative heat loss, I think most are pretty minor for a boil speed test.

If you’re really interested, I did the same type of test a few years back on Chowhound.


So, I guess the answer is: philosophical belief.

I don’t think that you’ve got your induction analysis right at all. That’s why I was hoping that you would have actual data to support your speculation.