The Brewers Association (US) offers the following style parameters:
"Light amber to mid-range brown in color, strong ales are medium to full bodied with a malty sweetness. Hop aroma should be minimal and flavor can vary from none to medium in character intensity. Fruity-ester flavors and aromas can contribute to the character of this ale. Bitterness should be minimal but evident and balanced with malt and/or caramel like sweetness. Alcohol types can be varied and complex. A rich, often sweet and complex estery character may be evident. This process often softens the perceived bitterness. Very low levels of diacetyl are acceptable. Chill haze is acceptable at low temperatures. (This style may often be split into two categories, strong and very strong.)"
Original Gravity (ºPlato): 1.060-1.125 (15-31.5 ºPlato)
Apparent Extract/Final Gravity (ºPlato): 1.014-1.040 (3.5-10 ºPlato)
Alcohol by Weight (Volume): 5.5-8.9% (7-11%)
Bitterness (IBU): 30-65
Color SRM (EBC): 8-21 (16-42 EBC)
Strong Scotch Ale
"Scotch ales are overwhelmingly malty and full bodied. Perception of hop bitterness is very low. Hop flavor and aroma are very low or nonexistent. Color ranges from deep copper to brown. The clean alcohol flavor balances the rich and dominant sweet maltiness in flavor and aroma. A caramel character is often a part of the profile. Dark roasted malt flavors and aroma may be evident at low levels. Fruity esters are generally at medium aromatic and flavor levels. Low diacetyl levels are acceptable."
"Chill haze is allowable at cold temperatures. Though there is little evidence suggesting that traditionally made strong Scotch ales exhibited peat smoke character, the current marketplace offers many Scotch Ales with peat or smoke character present at low to medium levels . Thus a peaty/smoky character may be evident at low levels (ales with medium or higher smoke character would be considered a smoke flavored beer and considered in another category). Strong Scotch Ales may be split into two subcategories: Traditional (no smoke character) and Peated (low level of peat smoke character)."
Original Gravity (ºPlato): 1.072-1.085 (17.5-20.5 ºPlato)
Apparent Extract/Final Gravity (ºPlato): 1.016-1.028 (4-7 ºPlato)
Alcohol by Weight (Volume): 5.2-6.7% (6.2-8%)
Bitterness (IBU): 25-35
Color SRM (EBC): 12-30 (30-60 EBC)
The BJCP offers the following style parameters:
9E. Strong Scotch Ale
Aroma: "Deeply malty, with caramel often apparent. Peaty, earthy and/or smoky secondary aromas may also be present, adding complexity. Caramelization often is mistaken for diacetyl, which should be low to none. Low to moderate esters and alcohol are often present in stronger versions. Hops are very low to none."
Appearance: "Light copper to dark brown color, often with deep ruby highlights. Clear. Usually has a large tan head, which may not persist in stronger versions. Legs may be evident in stronger versions."
Flavor: "Richly malty with kettle caramelization often apparent (particularly in stronger versions). Hints of roasted malt or smoky flavor may be present, as may some nutty character, all of which may last into the finish. ...."
Mouthfeel: "Medium-full to full-bodied, with some versions (but not all) having a thick, chewy viscosity. A smooth, alcoholic warmth is usually present and is quite welcome since it balances the malty sweetness. Moderate carbonation."
Overall Impression: "Rich, malty and usually sweet, which can be suggestive of a dessert. Complex secondary malt flavors prevent a one-dimensional impression. Strength and maltiness can vary."
History/Comments: "Also known as a “wee heavy.” ...."
Ingredients: "Well-modified pale malt, with up to 3% roasted barley. May use some crystal malt for color adjustment; sweetness usually comes not from crystal malts rather from low hopping, high mash temperatures, and kettle caramelization. ..."
OG: 1.070 – 1.130
IBUs: 17 – 35
FG: 1.018 – 1.030+
SRM: 14 – 25
ABV: 6.5 – 10%