Scottish ales are recipe and temperature dependent rather than being heavily process dependent. They are defined by maltiness and residual sweetness with a little bit of roast character. So mash temperatures should be high, 154–155 °F (67–68 °C) or even up to 158 °F (70 °C), and fermentation temperatures should be kept low. Those are the critical techniques required by the style.
Scottish ales need to be fermented at cooler temperatures than English ales to achieve their classic, yeast-neutral flavor profile. The esters and higher alcohols produced by fermenting in the 70s (~20 °C and up) are antithetical to what defines the style. Diacetyl and a bit of fruitiness are perfectly acceptable, but the big ester profile of an English ESB is not.
The right temperature is pretty much dependent on the yeast strain employed, but it is always going to be below 68 °F (20 °C). A reasonable starting point would be pitching the yeast into 60 °F (16 °C) wort and keeping the temperature at or below 65 °F (18 °C) for at least the first 48 hours. The fermentation should finish out in 4–5 days. If the beer takes longer than five days to ferment the temperature is too cold for that strain, if it takes three or less it is too warm. Letting the temperature freely rise to room temperature after the yeast has passed its major ester-formation stage in the first 48 hours helps achieve a timely fermentation.
The grain bill is really important to nailing the style. It should be simple — classically it is nothing but pale malt and a dash of roast barley. If the recipe uses floor-malted Maris Otter or another moderately-modified barley as its base malt then only 1–2% roast barley is otherwise required to duplicate what’s being poured in Scotland.
When the base malt is very well modified and produces relatively dry beers, brewers generally add a little caramel or crystal malt to give the beer a higher finish gravity. If the base malt will be an American or well-modified English malt, then the addition of 2–3% Crystal or 5–10% Carapils is necessary. The flavor contribution needs to be minimal for the beer to remain within the style characteristics. Caramel should never dominate the beer’s flavor.
For a more complex flavor profile add 10-20% Munich malt or 3-5% biscuit or amber malt to the grain bill. 5% oat flakes or 5-10% of oat malt will give the beer a bigger, very silky mouthfeel appropriate to the Heavy and Wee Heavy styles. Flaked barley can be substituted to give a full but drier mouthfeel.
Pretty much any British or German strain of ale yeast will produce good Scottish ale profiles if they are restrained by temperature control. Even lager yeast strains produce passable Scottish ales. Belgians successfully brew Scotch ales using house strains that are estery, phenolic and fusely at above 75 °F (24 °C) simply by fermenting at cooler temperatures.
The best strains to use are the Scottish, northern English and under-attenuating German alt strains, since they are specifically selected and cultured to complement sweet, malty beer profiles. They tend to be well-flocculating strains that leave lots of residual sugars behind. Strains that produce diacetyl are appropriate; a hint of butterscotch can really complement the style.
I prefer English varieties of hops, especially Fuggles for Scottish ales, but given the low flavor impact imparted by the hops just about anything but the American “C” hops (Cascade, Chinook, etc.) will produce good results. I like Fuggles because they contribute a fresh, worty hoppiness. Goldings or Northern Brewer contribute a little more assertive character that is more appropriate when brewing the export style. They are also excellent for balancing the huge sweetness of Wee Heavies; spicy German hops also really suit the Wees.
The hopping can be done in one or two additions. The bittering addition can be made at the start of the boil. A small flavor addition within the last few minutes is really optional for any of the styles except the Export.
Light and Heavy Scottish Ales should be conditioned for two weeks to a month and then consumed. They should have the edge worn off them by cold conditioning, but they are meant to be pub drafts and should be drunk young.
The Export style needs time to condition too. However it has enough bitterness and hop flavor to stand up to six months to a year or so of storage after it is kegged or bottled.
Wee Heavies need long, cool aging to develop character. It takes from six months to a year for them to begin to develop the propanol Scotch whisky aroma. Oxidation and aldehyde formation during aging adds complexity. Our experience at Vermont Pub & Brewery has been that the Wee Heavy flavor blossoms after 10 months of aging at 45 °F (2 °C), peaks at about three years and deteriorates after five.
Historically Scottish ales were gruit beers and remained so long after the German and English brewers had embraced the hop. Hops don’t flourish north of the Borders so Scottish brewers bittered and flavored their brew with the local heather and other heaths, meadowsweet, bog myrtle (sweet gale), juniper berries, spruce tips and broom.
With the high price and limited availability of hops it’s a synergetic time for homebrewers to replace hops with herbs and brew in the old style. Localvore brewers in the northern states and Canada can brew with what is seasonally available - spruce tips in late spring, bog myrtle and meadowsweet in midsummer, heather leaves and flowers in late summer, bog myrtle branches in winter and juniper berries year round.
I always say that for Scottish ale, accent the maltiness over the hop character. Depending on the type of Scottish ale (they get maltier as they go up), the general description for all of them is that they are malty over hoppy — so sort of the opposite of an IPA. I use some dark malt like chocolate and dark crystal so that you get a dark color but not so much of a roast flavor.
Some people also use peat-smoked malt, which I think is more of an American rendition. If you use too much peat-smoked malt, you can ruin your beer — if you cross the threshold you can’t do anything about it. One percent might be appropriate while three percent might be too much. Another problem with peat-smoked malt is if you use too much it can be too phenolic and smell like electrical fire and burning wires. If there are brewers that really like to start from scratch, I once brought peat back from overseas and smoked my own pale malt. It’s very mild compared to the commercial peat-smoked variety, so it is more forgiving.
For choosing hops, keep in mind that you’re not trying to get a whole lot out of them. I like to stay true to the style with Kent Goldings, Fuggles — mostly keeping with tradition and using the English varieties. Steer clear of any aggressive varieties. You do want enough bitterness to make sure it’s not too sweet, but not hoppy overall.
Temperature is important for these beers. Keep in mind the climate of Scotland. When fermenting a Scottish ale, I like to go with a low temperature — not low like 50 °F (10 °C) for lager — but the mid to low 60s (~15 °C) therefore reducing the esters. As for conditioning, the bigger it is the longer I’ll let it sit close to freezing. A lot of homebrewers don’t have the ability to do that, but get it as cold as you can.
When it comes to choosing yeast strains, there are specific Scottish strains, but any yeast strain that you can go with a slightly lower fermentation temperature will work. Keep in mind that some ale yeasts may not even ferment below 60 °F (15 °C) and you want a strain with low to medium attenuation.
Because we brew a lot of Kilt Lifter Scotch Ale, we start out with a basic North American 2-row. Traditionally you would use a nice cultivated malt from Scotland or England, which are expensive. But I think we can still make a great Scotch ale with our base malt by using very good English or German specialty crystal malts. There are lots of very good malts from overseas, and not to deny the US and the great roastings you can get here, but I’ve always had better success with quality specialty malts with Old World styling, plus it makes it more authentic in my mind.
A long 90 minute or 120 minute boil is important in Scotch ale because a lot of the malts you would normally use, such as English malts, have more dimethyl sulfides so a good long boil is important to drive off those nasty characters and have nice malty flavors.
When choosing yeasts, the thing you want to look at is that there is going to be more in the beer to ferment out, so you need something with a higher alcohol tolerance, say 10–11% tolerant. There’s going to be a lot of residual dextrins and the yeast get tired after working on the simple sugars before going into the complex dextrins. At the same time there will be a lot of alcohol already there. The vessel is also one of the most important things in brewing Scottish ale in my opinion. You really want to control that rising temperature that moves from the bottom to the top of the fermenter.
Scotch ales also need time to condition. If you take a look at wine, which can also be in the 8-12% ABV range, those high alcohol levels need more time to mature. This style is not something that you want to drink super-fresh. The flavors, nuances and dextrins start to mellow in the beer over time and I think time does a great service — it will turn Scotch ale into a delicious beer for several years to come.