Choosing charcoal

Choosing The Right Charcoal

Choosing the right kind of charcoal, can be a big dilemma for those who are inexperienced at the art of the barbecue. And even the experienced have problems. Some people swear by lump wood for its purity. Others insist on briquettes because of their even heat and consistency. So what are the differences?

The Theory

Lump wood charcoal is “true” charcoal and although sometimes treated with chemicals to make it easier to light, is usually unadulterated. It is made by burning wood in the absence of oxygen. In the old days, that used to be underground in buried pits. Lump wood charcoal is almost entirely used up when burnt, leaving very little ash.

Briquettes are a manufactured product from compressed wood charcoal and various other ingredients that can include types of actual mineral coal (lignite and anthracite) limestone, starch (to bind), wax (both to bind and assist burning), borax, sodium nitrate (to assist with combustion) and sawdust (combustible filler).

Some people say these chemicals affect the flavor of the food. Others say this only happens if you put the food on before the charcoal is ready, when those chemicals that are there to help it burn haven’t yet been burnt up.

However even lump wood is not all the same. I don’t mean the fact that not all pieces are the same size. Even batches and types differ. Some batches have large pieces. Others have small pieces. Some types of lump wood are dense and heavy. Others are light for their size and physically less dense.

The reason for this is that charcoal is produced from wood and not all woods are the same: different woods will produce different types of charcoal - both different densities and different proportions of non-combustible material. Also, although the process by which charcoal is produced is essentially the same and has been since time immemorial, there may be some slight differences depending on the available facilities and technology.


Choosing the right charcoal

In general, there are three variables to consider:

● The temperature at which it burns (“power density”)

● The time duration for which it burns (“energy density”)

● The amount of ash left after it has finished burning (“residue”)

The terms in brackets are for the benefit of physicists. The rest of you can ignore them.

And for the benefit of the mathematicians among you, any two of these variables are independent and the third is dependent. But what does that mean in practice?

The amount of time a piece of charcoal burns depends upon its weight.


● A large piece will burn for LONGER than a smaller piece of the same physical density.

● A heavy piece of any size will burn for LONGER than a lighter piece of the same size.

The temperature at which a piece of charcoal burns depends upon its physical density.


● A less dense piece will burn HOTTER than a denser piece.

● A small piece will burn at the SAME TEMPERATURE as a larger piece of the same physical density.

It should be clear from the above that charcoal can either burn hotter for less time or less hot for more time. The larger, dense pieces burn less hot for a more time. The larger but less dense pieces burn hotter but for less time. While the smaller dense pieces burn less hot and for less time (because they are smaller).

But all of this presupposes that all the charcoal fuel gets burnt up. In practice, some of it is left as ash. That means that if a piece burns both very hot and for a long time, it is going to leave less ash behind at the end than another piece of the same size that burns at the same temperature for less time.

Think of the charcoal that burns longer as nearly pure fuel and the other as adulterated fuel. That is essentially what it is. In practice. I don’t mean that it’s deliberately adulterated. Unlike briquettes, lump wood charcoal is not usually adulterated with chemicals or additives. However, no charcoal is pure carbon. It is made from burning wood without oxygen and there are always other chemicals present as well, including potassium. These chemicals do not burn and are left over afterwards as ash residue

Thus, briquettes leave behind more ash than lump wood and don’t burn as hot as even the denser lump wood charcoal. But do burn longer.

The following table illustrates this set of relationships more graphically:

BIGGER LUMP WOOD High temperature Short duration Not much ash Intermediate temperature Long duration Not much ash
SMALLER LUMP WOOD High temperature, VERY short duration Not much ash Intermediate temperature Short duration Not much ash
CHARCOAL BRIQUETTES Lower temperature Longer duration A lot of ash


Choosing the right charcoal

In Practice

Okay, but what does all this mean to you as a customer trying to make up your mind about which charcoal to buy?

Well, as there is a tradeoff between temperature and how long the charcoal burns, the first thing you need to think about is what you will be cooking and how long you will be cooking it.

For example, will you be cooking burgers and sausages over an open grill? If so you want something that will cook them quickly but not something that will continue to give out heat long after you’ve finished cooking. This could come from smaller pieces of charcoal. They won’t burn too long, but they also won’t burn too hot for sausages that can be quite vulnerable to burning. Also, if the pieces of lump wood are small, they will not be too high or too close to the food rack.

On the other hand, if you are cooking steaks, you will want something hotter but at the same time, you still don’t want the charcoal to be spewing out heat long after you’ve taken the steaks off and are sitting down to eat. That would just be wasted heat. So, for that you would want large but light charcoal. (See our review article: Flavor from the Fire II - smoker boxes, lava rocks and charcoal for comparisons of different brands of charcoal.) One observation we should make about this hot but fast burning charcoal is that it produces very little smoke (remember that smoke is the result of less oxygen and a slower burn rate). So, if you want smoke with this type of charcoal, you need to throw on a few wood chips.

But if, instead, you are cooking something for longer on the barbecue, or for a very long time in the smoker, you will want large and dense “restaurant grade” charcoal. This is available from several suppliers and reviewed on this site (see above). The reason that restaurants use this kind of charcoal is because they are cooking all day and they need to keep it up without having to top it up or start again and relight the grill.

You may have noticed that we haven’t mentioned briquettes. That’s because we at don’t really like them. But we’re open to persuasion.

Also remember that you can also use wood chips and wood chunks for flavoring. Again, remember, the principles are the same as for charcoal, more or less. For a medium or long cooking or smoking session, use wood chunks. For a short session, especially using an open grill, use wood chips.

And don’t forget to write in and share your experiences with us.

Happy Barbecuing!

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