There's a lot of confusion surrounding this term, so I'll be very clear. A maceration involves soaking plant material in liquid for so long it becomes a pulp. The liquid can be anything from water to alcohol to vinegar. This method take a long time and is quite irritating (because sometimes it all starts to ferment on you and you have to start all over again). Luckily, macerations aren't all that common in modern herbology.
This one should be easy enough to remember because to make an expression you "express" the liquid directly from the plant material. Note that you are not adding any of the plant material to your preparation. There should be no pulp in your expression. Think of it like making orange juice. You can squeeze the orange to get a pulp-free expression or you can twist the orange on a juicer to get a pulp-juice mix. With expressions you are after just the juice, not the pulp.
Expressions are not easy to make at home unless you have the right equipment. If you want to make your own expressions, invest in professional-grade equipment to assist you.
- a large pot
- a screen suspended in the vertical center of your pot
- a domed lid for the pot that does not have a handle
Now you can either make a cold water percolation or a warm water percolation. Fair warning: cold water percolations take a LONG time. Days. Many, many days. If you warm the water gently, the entire process happens faster (though still not fast). Either way, you should see water condense on the lid as it evaporates, roll down to the tip of the dome, and drip onto the herbs. You can speed up the process by putting ice on the inverted lid, but it will still take a while. This is not a method I recommend at home because of the frustrations involved.
I'd rather eat glass than make a reflux at home, so do yourself a favor and leave the refluxing to the professionals. Refluxes are basically percolations using something other than water. Alcohol is the most common. Since alcohol tends to ignite on the stove, you absolutely must have professional equipment for this method. And hopefully a processional to show you how to do it. Don't do this at home.
As you can see, some of these methods are easier to pull off at home than others. Most recipes you will encounter will either be tinctures or infusions (or may just use the whole herb instead), so you don't really need complicated equipment. Just space to store your creations.