Curiosity recently lead me to look over my brewing records with an eye to the national origin of the beer styles I've brewed. It turns out that 38% of my batches are Belgian style ales (for comparison, 26% are UK styles, 7.5% are German wheat beers, and only 3.7% are US styles). It occurred to me that I've been mentally following certain guidelines worked out over those 38%. So, in what will likely be the first of many 'editorial' posts in which I go rogue and give you opinions rather than facts, I figured I should share those guidelines. Call it the Ten Commandments of Belgian ale.
Belgian beers create complexity from simple ingredients. Not too simple. Blending pils malts—and your base should be pils—from different maltsters or sources keeps things simple, but not too simple. A number of Trappist breweries use the same strategy, so it's got some pedigree.
Pale Belgian ales should be dry. Though they shouldn't be thin or lack head retention, you don't need any crystal malt (not even carapils) to achieve this. A small percentage of crystal malt can enhance the profile of dark Belgian beers like quads, but it shouldn't stand out as identifiable. The next time you want to add lots of crystal malt, remind yourself that Westveleteren 12 has no crystal malt. Zero.
Pale or dark, low or high abv, Belgian ales should be drinkable. You shouldn't feel bloated after a glass of even an 11.3% beer like Rochefort 10. Using simple sugars in the recipe can get you there, making the beer feel less heavy despite the alcohol punch. With beers under 7% like Trappist singles or standard saisons, the yeast and process should produce the dryness you want without need for any sugar.
Notice I said 20% of fermentables, not 20% by weight. In other words, up to fifth of your starting gravity points might be from sugar. Whether a fifth of the weight in your recipe is sugar will depend on how efficiently you're extracting fermentable material from your grain, which varies between systems and brewers. I find it helpful to calculate the starting gravity of a 'sugarless' version of a recipe with my expected efficiency, then add sugar to the calculation until I get the percentage of fermentables I want.
In some ways, beer is a simple beverage. It doesn't have many ingredients besides the base of water—just hops, grain (maybe sugar) and yeast—so it's best when only one of those is in a forward position. With American beers, it's the hops; with German lagers, it's the grain; and with Belgian ales, it's the yeast. The other elements should be there as complements, not competitors. But aggressive American hops will compete and clash with the yeast profile. The best Belgian beer with US hops that I've had is La Vermontoise, a collaboration between Blaugies and Hill Farmstead. And even it didn't seem right. So save the Cascade and Simcoe for a beer where it has room. You might be able to get away with noble-type US hops like Liberty, but only because they can stand in for continental hops.
Remember how I said the beer should be dry, but not seem thin or lack head retention? Step mashing is how you hit all three points at once. Combining a low temperature saccharification rest (say 144-48) with a high one (say 156-62) will give you a low final gravity with long chain sugars leftover for body. A quick protein rest enhances things even more and can improve head retention. I know that mashing everything at one temperature for an hour is quicker and easier. Do you think I like babysitting a mash for 2 or 3 hours? But Spinoza was right when he said "all things excellent are as difficult as they are rare."
If you tend to brew American style ales, you're probably used to keeping the fermentation temperature below 68F no matter what. That's a good thing to do if you want a great American ale. Or a boring Belgian ale. Fermenting Belgian yeast cool is like playing heavy metal softly. Add your yeast when the wort is at least 4F or 5F cooler than your desired fermentation temperature. If the fermentation temperature (which you can predict with this) doesn't peak at 70F or above, you're missing out on what Belgian yeasts can do. For saison yeasts, make it at least 80F.
Samuel Smith's ales, Czech pilsners, and Westvleteren wouldn't be what they are without open fermentation. And many other Belgian brewers still use wide, shallow vessels even when they switch to closed fermenters. The geometry of a wide, shallow fermenter can ramp up ester production and the open fermentation allows easy access to oxygen whenever the yeast want it. Don't worry about oxidizing the beer—just close the fermenter once the krausen starts to fall.
Generally speaking, following the usual guidelines of .75 million cells per ml per degree Plato is fine. But if your yeast is really itching for a fight, it can handle more action. A smaller number of yeast cells will also need to divide more times to hit a sustainable population, and multiplication is where most flavor products are made. In other words, 300 Spartans is better than 600 couch potatoes. If you grow up the right number of cells with a standard starter, then keep them happy with a vitality starter—add some extra wort a few hours before pitching—they'll be at their best when they get to work.
My lovely and amazing wife and I did an experiment. I bottle conditioned some of a batch and kegged the other part. We tasted both. Guess which one was richer and more interesting? You'll notice some bottle conditioned beers say 'refermented in the bottle' on the label. This isn't just fancy talk. The yeast in the bottle generates a second, miniature fermentation that adds new fermentation byproducts to the beer. These are trapped in the bottle, ending up in your glass rather than being blown off. The result is an extra layer of goodness.
The ideal Belgian ale will be topped with a thick layer of dense foam the texture of shaving cream. The beer should be lively. Champagne should be jealous. So when you're picking bottles to condition your beer in, pick thick ones. I prefer around 3.2 to 3.5 volumes myself.