When cooking with different pans you’ve probably noticed that they heat up at different speeds and some pans hold their heat better than others. This is all to do with the construction of the pan and the metals that have been used.
Different metals have a different thermal conductivity. This is a measure of how well heat is transferred through the material. They also have different heat capacities, which is the energy required to heat a piece of metal (such as your pan), and therefore the metals ability to store more heat and hold onto it for longer.
Typically you will find that more expensive pans use metals which have a higher thermal conductivity but these same metals have a higher price tag. This is typically why expensive pans perform better than cheap ones.
Which Metals Are Best?
We can combine a measure of both the thermal conductivity and heat capacity into a single measurement, called the thermal diffusivity. Using this single number, common metals used in cookware can be ranked as follows (items towards the top of the list are considered “better”).
- Cast Iron
- Carbon Steel
- Stainless Steel
However, in reality, this doesn’t tell us what the best metals really are. After all, there is more to it than just how well each metal handles the heat. You might think that looking at this chart, we should just make all pots and pans from copper. However, there are drawbacks to using certain materials.
Reactivity, Cost and Durability
Some metals will react with our food to make them taste bad, or even worse to make us ill. Both copper and aluminium, which topped our diffusivity chart, react badly with food. Copper can cause liver and kidney problems, and aluminium has been associated with Alzheimer’s disease. Ingesting tiny amounts of copper and aluminium may not do you much harm, but extended exposure could lead to real problems.
Another drawback to making our pots and pans from copper and aluminium could be the cost and the durability. Copper is the most expensive of the materials in our list and it scratches easily. Although with proper care a copper pan will last you a lifetime, you won’t be able to put it in the dishwasher, and you may find that it loses its lustre over time.
Luckily, there is a way around both of these problems by combining different metals together. A pan could be constructed with a copper base, but then have the rest of the pan constructed from stainless steel to prevent contamination of the food. This would give us a more evenly heated pan that comes to temperature quickly, with less of the health risks. This would also bring down the total cost of construction.
The way that a pan is put together will also impact how well it performs. When you place a pan on your gas burner, you are exposing the bottom of the pan to a number of hot spots directly over the flames. If your pan has a very thin base and a low thermal conductivity this effect will be amplified. The burners will heat up the areas of the pan directly above them very quickly, and the rest of the pan will not be able to pull the heat away quickly.
By building a thicker base into a pan, we can alleviate this problem, but at a cost. It will take longer for the heat from the burners to reach the cooking surface within the pan, but the heat will arrive more evenly. You will get a better cooking experience, but it will take much longer for the pan to come up to heat in the first place.
With this in mind, the best pans will have thick bases made of metals with a high thermal conductivity. This is why copper bottom pans are so popular. The higher thermal conductivity means that the pan heats quicker, compensating for the thicker construction.
Pros and Cons
Let us take a look at each of our metals in turn and discuss where their strengths and weaknesses lie.
Copper has a high thermal conductivity, which means that it will heat up very evenly (especially with a thicker base) and is very responsive to changes in heat. This means that when you change the temperature of your hob, the pan will change with it quite quickly. This can be a plus or a negative, depending on whether you need your pan to hold onto heat.
Copper is extremely expensive, heavy and easy to scratch. On top of that, it can react with your food and cause health problems. This means that it is best used in cookware when combined with another material such as stainless steel. A lined copper pan will make a brilliant tool for cooking on the stove top.
Aluminium combines a high thermal conductivity with low cost. However, like copper, it can react with your food. A common solution to this is to coat the pan with Teflon, which has the added benefit of making your pan non-stick.
However, a plain aluminium pan can be used with non-reactive foods such as water (for cooking eggs or pasta) and stock. As an alternative to a Teflon coating, aluminium may be anodized (which creates a hard aluminium oxide coating) which will also prevent a reaction. Coating with stainless steel is another option but tends to be expensive.
Coated aluminium pans make great all-rounders without breaking the bank. This is likely to be the kind of pan most people have in their kitchen (particularly if they like Teflon).
Cast iron has a fantastic ability to hold onto heat – way beyond other materials. Combined with its low cost of manufacture, this makes a cast iron skillet a must have for serious cooks. Cast iron cookware tends to be heavy duty, which leads to even heating, but its low thermal conductivity means that it can take a while to come up to heat.
Cast iron can also react with acidic foods and so must be carefully seasoned to avoid this from happening. However, once seasoned these pans are pretty bulletproof and easy to look after. Cast iron skillets and griddle pans are particularly popular.
In theory, carbon steel should perform fairly similarly to cast iron. The only difference between the two is the ration of carbon to iron. However, because of the manufacturing methods used for carbon steel pans, they tend to be thinner and more lightweight. As carbon steel has a low thermal conductivity this can lead to low heat retention and hot spots in the pan. So, be sure to look out for thicker built examples. Having said all of that, carbon steel pans can make great frying pans and woks. As with cast iron, they will need to be seasoned to keep them non-stick.
A pan made entirely from stainless steel is likely to be unpleasant to cook with. However, it’s a great material when used in conjunction with others. It’s low cost and extremely durable, being easy to clean and difficult to scratch. Stainless steel also makes a great material for things like mixing bowls, whisks and other kitchen equipment.
The Best of All Worlds?
Hopefully what you are taking from this article is that no one metal gives us everything that we need. Perhaps the best solution is to use something like “tri-ply” cookware. This is cookware where the pan has been made from layers of material, usually copper and aluminium on the bottom and then stainless steel for the top. Some more expensive pans will have the outer material all around the sides too, which will give even heating around the side of the pan.
However, different cooking styles and personal preferences will often determine what the best pan is for you. I hope that with this article you can make a bit more sense of the sales materials next time you come to buy a new pan, and you can get the best possible to fit your needs and your budget.
If you’ve got any tips – please leave them below in the comments!