Outdoor grilling is a very popular method of cooking. In
fact, approximately 75 percent of U.S. households have a
grill. A grill consists of a cooking surface, typically
made of parallel metal bars or a porcelain-covered metal grid,
over a fuel source capable of generating intense heat, usually
up to temperatures of 500 degrees Fahrenheit (260 C) or more.
Grilling is done all year, but is most
popular during the spring and
There are several different types of grills, but gas
and charcoal are by far the most common.
In this edition of HowStuffWorks,
you will learn about the parts of a grill and how they work
together. You'll learn what charcoal is and how it is made, as
well as about the differences between liquid-propane
(LP) and natural-gas grills. You'll also find out about
other less-common types of grills and their fuel sources.
Let's start by taking apart the trusty charcoal grill.
Fire Up the Charcoal
The components of a
grill can range from very simple to incredibly sophisticated.
The simplest grill is a charcoal burner and has three
- Cooking surface
- Charcoal container
- Grill support
A common version of this arrangement uses a shallow, round
container mounted on a metal tripod, with a round cooking
grill that rests on top of the container. Look at the example
A simple charcoal
Charcoal grills can be more complex than this -- some have
a hood to cover the grill and additional tiered
cooking surfaces -- but the basics are the same.
The fuel source for charcoal grills has been around
for at least 5,000 years. No one is certain who discovered
charcoal or even what civilization first used it. Evidence of
charcoal has been found all over the world. It was even used
embalming process for Egyptian mummies!
You may not realize it, but charcoal is not a rock or even
some type of coal. It is actually wood! Charcoal is
created by heating wood to high temperatures in the absence
of oxygen. That is, you take wood, put it in a sealed box
or clay and heat it to about 1000 F (538 C).
Why would you go through such a tedious process instead of
just burning the wood as it is? Freshly cut wood contains a
lot of water -- sometimes more than half its weight is water.
Seasoned wood (wood that has been allowed to sit for a year or
two) or kiln-dried wood contains a lot less water, but it
still contains some. Watery wood does not make for very
efficient cooking. Also, when the tree was alive it contained
sap and a wide variety of volatile hydrocarbons in its
cells. "Volatile" means that these compounds evaporate when
While it may not look like it, charcoal is
When you put a fresh piece of wood or paper on a hot fire,
the smoke you see is those volatile hydrocarbons evaporating
from the wood. They start vaporizing at a temperature of about
300 F (149 C). If the temperature gets high enough, these
compounds burst into flame. Once they start burning, there is
no smoke because the hydrocarbons turn into carbon dioxide and
water (both invisible).
This explains why you see no smoke from a charcoal
fire (or a fire that has burned down to embers). This process
drives off all of the volatile organic compounds and leaves
behind pure carbon and ash (the non-burnable
minerals in the tree's cells). When you light the charcoal,
what is burning is the pure carbon. It combines with oxygen to
produce carbon dioxide, and what is left at the end of
the fire is the ash -- the minerals. This produces a very
intense heat with very little smoke, making charcoal very
useful as a cooking fuel that will not overwhelm the flavor of
the food with the elements found in normal woodsmoke.
Grilling enthusiasts passionately argue the merits of
charcoal versus gas grilling, citing especially the difference
in flavor. Charcoal does provide a distinctive flavor
that is not easily reproduced. It is a tough decision for many
people: the convenience of a gas grill against the flavor of
charcoal. Let's take a look at gas grills and how they work.
Cooking with Gas
Even the simplest gas grill
is more complex than a typical charcoal grill. Common
components of a gas grill include:
- Gas source
- Valve regulators
- Cooking surface
- Grill body
- Grill hood
Components of a gas
The grill body houses all of the other components
except the hood. The hood covers the cooking surface
and serves to trap the heated air inside, which increases the
temperature inside the grill.
The gas source is connected to the valve
regulators via the main hose. The regulators are
controlled by knobs that allow you to determine how much gas
is allowed through the valve to the burner. Most grills have
two main burners, with a regulator for each one. Each burner
has a series of tiny holes along its length that the
gas exits through.
Three things are required for a gas grill to ignite
The gas is supplied from the propane tank or the
natural-gas pipeline (more on this in the next section), and
oxygen comes from the air. But where does the
spark come from?
Making Sparks Fly
The spark usually is
supplied by the grill starter, sometimes called the
igniter. This is a push-button or rotating knob that
creates a spark of electricity to ignite the gas. The starter
uses piezoelectricity to generate a nice spark that
lights the grill.
The starter on this grill uses a knob that
to trip the
Certain crystalline materials (like quartz, Rochelle salt
and some ceramics) have piezoelectric behavior. When you apply
pressure to them, you get a charge separation
within the crystal and a voltage across the crystal
that is sometimes extremely high. For example, in a grill
starter, the popping noise you hear is a little spring-loaded
hammer hitting a crystal and generating thousands of volts
across the faces of the crystal.
Turning the knob on this grill causes the
spark to jump between the two
A voltage this high is identical to the voltage that drives
a spark plug in a gasoline
engine. The crystal's voltage generates a spark large
enough to light the gas in the grill.
Burners in gas grills often look like
flattened "O"s riddled with small
The burner is where all the actual burning occurs.
It mixes the gas with oxygen and spreads it out over a large
surface area to burn. Each burner has a pair of
electrodes connected to the starter. When the starter's
hammer is tripped, the resulting surge of electricity causes a
spark to arc across these electrodes and ignite the gas/oxygen
mixture. To create an evenly heated cooking surface, most gas
grills have at least two separate burners.
It's a Gas!
The majority of gas grills use
metal tanks full of liquid propane (LP) gas. LP gas has
the advantage of coming in a portable tank, and it is
available nearly everywhere, whereas natural gas uses a pipe
connected to the gas main at your home.
Why can you get LP gas in a tank but not natural gas?
Propane normally changes from a liquid to a gas at -46 F (-43
C). However, propane has the nice property that when you
compress it, it condenses into a liquid and will stay
that way until it is uncompressed. This means that propane is
much easier to store in a tank than natural gas, which does
not easily compress. Because natural gas doesn't compress well
into a liquid form, it is typically delivered via a dedicated
pipeline to your home.
Another benefit of LP is that it contains much more energy
than natural gas. A grill's cooking capability is rated in
British thermal units (BTU). A BTU is the amount of
heat required to raise the temperature of 1 pound (0.45 kg) of
water 1 F (0.56 Celsius). A cubic foot of natural gas contains
something like 1,000 BTU of energy. One cubic foot (1
ft3) of propane contains
perhaps 2,500 BTU. Grills typically range from 20,000 BTU to
about 50,000 BTU. A higher BTU rating normally indicates a
larger grill with a greater cooking surface.
Most gas grills use a propane tank like this
On a grill, you can see the difference between natural gas
and LP most easily by looking at the pipes connecting
to the burners. The pipe on a natural-gas grill is about twice
as big as the one on a propane grill. Natural gas is mostly
methane but contains significant quantities of other
compounds, including butane, ethane and propane. You normally
would only buy a natural-gas grill if you plan to connect it
directly to a gas pipe in a permanent location and if natural
gas is available in your area.
Propane?Propane is created
and contains aliphatic hydrocarbons --
hydrocarbons composed of nothing but hydrogen and carbon
atoms. When you take petroleum and process it in a refinery,
you end up with hydrocarbon chains of different
lengths. These different chain lengths can then be
separated from each other and blended to form different
fuels. For example, you may get methane, propane and
butane. All three are hydrocarbons:
- Methane has just a single carbon atom and
four hydrogen atoms (CH4).
- Butane has four carbon atoms and ten
hydrogen atoms (C4H10).
- Propane has three carbon atoms chained
together with eight hydrogen atoms (C3H8).
Grilling Alternatives and Options
move beyond the basic grill design, most manufacturers offer
several options to enhance your grilling abilities. Some of
these options are:
- Multi-tier grills - There are grills that add a
second and even a third cooking surface above the main one.
Because the temperature drops considerably as the distance
between the cooking surface and fuel source increases, the
second cooking surface is typically used for things like
steaming vegetables and keeping cooked meat warm.
- Side burners - By running a hose on a gas grill
to a small burner attached to the side of the grill,
manufacturers provide a way to cook sauces or other foods
that need to be in a pan or pot.
- Rotisserie - This is a long metal rod suspended
horizontally above the fuel source and rotated slowly,
usually by an electric
motor. It is used primarily for slow-roasting poultry or
Electric grills are very popular, especially
with people who cannot have an outdoor
While charcoal and gas grills are the most popular, there
are alternatives. The most common is electric. An
electric grill has a heating element either embedded
within the cooking surface or directly below it. A drip
pan catches the grease and fat that cooks out of the meat.
Electric grills are typically portable, and most are small
enough to place on a table or countertop. Unlike gas or
charcoal grills, electric grills can be used indoors.
Another type of grill that is catching on at the premium
end of the market is infrared. Infrared grills use
special ceramic-plate burners that radiate infrared
heat. According to Thermal
Engineering Corporation (TEC), infrared grilling does not
dry the meat out and can generate a much higher temperature
(up to 1,650 F / 899 C) than any other type of grill.
Be sure to check out the links on the next page for more
information on grills, grill manufacturers and related topics.
Lots More Information!
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