Let me start by being honest: I've been really looking forward to writing this post for longer than I'd like to admit. The reason you should apply beard oil right after a shower is a beautifully complex physics problem that highlights the utter simplicity of nature. Like all natural science, it boils down to a complex simplicity, and I love it. So let's talk about it:
Let's rehash The Bearded Savant's recommendation: we suggest you apply beard oil after a shower when your pores are open and your beard is damp, but not wet. Beard oil, as the name suggests, is an oil and oil is hydrophobic. Water and oil don't mix. Water and oil meeting on your facial hair are no different. And this is where the physics goes from cool to freaking awesome.
The atmosphere you saunter through day-to-day is normally well below saturated (unless you live on Mt. Washington, but if you do you get to do this, so you might still come out on top) . As a result, the moisture on your beard wants to evaporate. If you would like to read more on why this is, I suggest brushing up on vapor pressure and partial pressure, but drink some coffee first. The dryer-than-your-beard atmosphere will actually draw the dampness of your beard to the end of the individual hair follicles, because this is where the evaporation is taking place and as the water at the end of your follicle is evaporated, more is drawn in to take its place. Because beard oil is hydrophobic , it will migrate up the follicle, towards your skin, and in the opposite direction of the water. The evaporation of water draws beard oil against your skin, isn't that cool! When this happens in conjunction with more receptive pores, you get maximum absorption of the the beard oil and maximum effectiveness of the carrier/essential oil combinations.
Care to test this? Put some beard oil on right after a shower (when your facial hair is damp but not wet), noting how much you apply. Later in the day, hours after your beard has dried, try applying the same amount of beard oil and you will notice that as you pull your hands away, your hands will feel more oily, that is, there will be more residual oil not taken up by your beard. It is pretty impressive!
This also informs us of a handy beard oil saving trick: No matter how hard you try, if you apply beard oil onto a dry beard, it will not absorb as much oil. Knowing this we can use less oil on a dry beard and more on a damp beard, allowing us all to use our product more effectively. Science informs efficiency and efficiency saves you money. Ergo, science saves you money.