Maker’s Mark has been doing some cool stuff with special releases lately — for a recap, check out my pieces on the Wood-Finishing Series here and here — but this one truly takes the cake for anyone interested in the science behind bourbon.

The new Entry Proof Experiment will hit shelves later this month — you’ll most likely find it at the distillery gift shop, and if you’re a member of The Whisky Drop* Maker’s club, you’ll be getting the bottles in the next two installments. Basically, there are four bottles in this release, and all four come from an experiment held at the distillery in 2013.

To see how much impact barrel entry proof has on the taste profile of their bourbon, the folks at Maker’s Mark entered the bourbon into barrels at four different proof levels: 110 (which is what Maker’s has used since the beginning but is considered low in the industry), 115, 120 and 125.

For a quick explanation, entry proof is the proof of the distillate before it goes into a barrel. Many distilleries opt to put it in around 125 and then add water when it’s done aging, thus saving money on the amount of barrels needed. Some choose a lower number — like 110 — which was more common before and right after Prohibition because some believe by adding the water up front, it produces a better-tasting, nuanced bourbon.

Barrel entry proof is just one of the many bourbon-making components that can be manipulated to produce a different result. There’s no right or wrong number here — by legal definition, you can’t enter it into a barrel higher than 125 proof — it’s just the preference of the distillery and its master distiller as to when they want to add the water (before or after it ages).

So anyway, Maker’s decided to play around with the four different entry proofs, and they figured they’d let their fans get a taste of the experiment as well. The cool thing about these four bottles is that the age of the whiskey inside is about 8 years old — definitely older than the standard Maker’s Mark. So just taking that into account, it’s a rare release you’ll want to have in your collection. Plus, these are bottled at barrel-proof, so here’s your chance to try 8-year-old Maker’s Mark at cask strength!

I was invited to a media tasting and explanation of the DNA Project, and I was blown away by the completely different flavors each sample produced. Even someone new to bourbon would be able to tell the differences between each sample.

I was partial to the first sample — 110 — as was the majority of the group. The flavors were more rich, and that familiar Maker’s Mark mouthfeel was present from the first sip to the last.

The other three expressions had some funky flavors — the 120 proof even had strong pineapple notes, which is crazy — and it was easy to see why the founders of Maker’s Mark chose 110 and have stuck to that ever since, even though it ultimately costs them more money.

What this experiment shows is, yes, barrel entry proof does indeed have a pronounced effect on taste profiles. And the best news is that you can try it for yourself.

Maker’s suggests buying the entire four-bottle set (at $99 per bottle), but they will also be sold individually at the distillery and various bars and liquor stores in the area. The bottles are 750ml, and with a purchase of the set, you also get handmade posters from Louisville’s Hound Dog Press, which partnered with Maker’s for this release.

There are only 2,400 sets available, and the release is staying in Kentucky. Each poster will be numbered to match your bottles. Look for these later this August and tell me which one is your favorite.

*Speaking of The Whisky Drop, I hear they’re expanding the membership to more folks in Kentucky and Washington, D.C., so if you want to sign up for that, click here. It’s a membership service where you get two special bottles in the mail every couple months or so.