As with any topic in barbecue, everything is an argument and people have their own ideas about what is best. This even includes things like the orientation of brisket and whether or not the fat cap should be up or down in the smoker.
In general, the fat cap of the brisket should be oriented towards the heat source. The fat cap functions as an insulator and helps to prevent the flat from drying out.
Animals like steer use fat (Adipose tissue) for energy storage as well as the regulation of bodily temperature.
There are several types of fat found on an a steer - subcutaneous, intermuscular, intramuscular, intercostal, etc.
This article explores the solid subcutaneous animal fat that sits on top of the brisket. This fat is referred to as the "fat cap."
The brisket comes from the chest of the steer. The side of the brisket that faces the skin is covered with a layer of subcutaneous fat - this fat is referred to as the fat cap.
On a whole packer's brisket, the fat cap layer is rather thick, usually 1-2 inches - however, the thickness of the fat cap depends entirely on how the steer was butchered.
It's typically recommended to trim the fat cap down to roughly 1/4 to 1/2" thick as you're not going to entirely render 1-2 inches of fat; Nobody would want to eat that much fat either.
Rather, you can trim this fat and save it for beef tallow. Keep in mind, trimming too much fat can also affect the structural integrity of the brisket.
Trimming is done to make the brisket "aerodynamic." Meaning, we maximize airflow inside the smoker.
Things like protruding nodules and boxy angles will affect airflow (can you identify the boxy angles above?). These protrusions are apt to dry out, which you don't want.
Their are three main opinions when it comes to brisket's placement on the smoker; Either up, down, or flipped.
However, they all really boil down to one concept:
The brisket's fat cap should face the heat source to function as an insulator. Meaning, the smoker you own and use matters.
To illustrate:
Say you're following a recipe online for smoking brisket.
If the person owns an offset smoker, they'll likely tell you to orient the fat cap up. What they fail to tell you is that they're doing this because the heat is coming from the top. They also likely orient the point end towards the firebox.
The picture below demonstrates the general flow of heat inside an offset smoker:
However, if you own a Weber Smokey Mountain you'd want to orient the fat cap down because there is radiant heat from the bottom due to the heat baffle.
Here is a picture of the heat flow inside a Weber Smokey Mountain:
If you own a pellet smoker, you may start smoking with the fat cap up due to the radiant heat from the baffle, but flip the meat after a period of time so that the fat cap is down.
This way, your bark is set on the lean and won't wash away as moisture pools and fat renders.
The general flow of heat inside a pellet smoker is pictured below:
These days, almost all my briskets are cooked on my Weber Kettle with a Slow N' Sear.
Since the heat rolls over the top of the brisket, I orient the fat cap up.
With this idea in mind, almost all people who smoke on an offset smoker will orient the brisket with the fat cap up as the as the heat rolls over the top and out of the smokestack.
I already demonstrated the flow of heat in a regular offset smoker but even on a reverse flow offset smoker, the heat functions in a similar way.
Keep in mind, in this example, the point would be oriented in the opposite direction due to the lower baffle.
I remember when I first got started smoking brisket, I saw on barbecue forums a number of people said to do fat side up because it provides "moisture" to the meat.
Meaning, as the fat starts to render it will penetrate the meat.
That doesn't make sense.
I quickly ignored these ideas because I remembered a demonstration from my 5th grade Teacher where She combined lipids (Fat) and water in a glass.
As you might expect, the fat and the water never combined - fat is non-polar and water is polar - and the fat sat on top of the water.
Meaning, this idea that somehow the fat could penetrate the brisket (which is primarily water) made no sense.
You will also hear folks say the fat can render and then braise the meat. This idea I can more-so get behind and is a big reason for why I foil boat all of my briskets.
Foil boating allows the fat cap to continue to render (which improves bark) and for water to collect on the bottom. The meat juices will then braise (slow cook in a liquid) the meat side of the brisket.
The added benefit of the foil boat is that it preserves the "sugar cookie" bark that can become ruined through Texas crutching with aluminum foil or with wrapping in butcher paper.
With the purpose of the fat cap to act as a heat shield, there are several smokers that require you to orient the fat cap down.
Apart from Kettle Grills/Smokers and Offset smokers, almost all other types of smokers should orient the fat cap down because that's where the heat source is.
For example, in an electric smoker you have the heat source at the bottom:
Electric smokers are also very insulated. In most cases you don't even have to wrap because there is so much humidity within the smoke chamber which helps prevent the brisket from stalling.
The same could be said for gas smokers:
The only time I've ever flipped my brisket mid-cook was with my pellet smoker.
Pellet smokers work primarily based on convection heat (like your oven). However, there is also radiant heat from the bottom as that's where the heat source is (the firepot).
Meaning, you can start the cook with the fat cap up to set the bark on the lean side. This helps to prevent the rub from washing away as moisture wicks and fat renders.
You can then flip the brisket so that the fat cap can function as a heat insulator and so that the fat can start to render.
In my opinion, on other smokers, flipping isn't necessary. Granted, I'm also apt to be as lazy as possible.
This is a quick cheat sheet for folks to reference. It simply lists the different types of smokers and if the fat cap should be up or down.
Note: This table isn't all encompassing. I did my best to list the most common types of smokers and cookers used.
| Type of Smoker | Fat Cap Up, Down, or Flipped |
|---|---|
| Offset smoker (standard and reverse flow) | Up |
| Weber Smokey Mountain (WSM) as well as most water smokers | Down |
| Pellet Smoker | Flipped |
| Weber Kettle | Up |
| Electric Smokers | Down |
| Gas Smokers | Down |
| Gas Grill | Down |
| Ugly Drum Smokers | Down |
