Scotch Ales are strong ales, also known as "Wee Heavy", from the late 1800s when Scottish brewers commonly sold their strong ale in small 6oz bottles called “nips” or “wee” bottles." In 19th century Scotland, they'd also be known as 160/-, a nomenclature based on the now obsolete shilling currency. Scotch Ales traditionally go through a long boil in the kettle for a caramelization of the wort. This produces a deep copper to brown colored brew with a tan head. Scotch Ale is dark, heavy and strong with a bittersweet, sometimes slightly metallic tang and also very malty in character and is generally fairly full-bodied. Very rich malt aromas and flavors evoke a caramel, nutty character along with characteristic flavors from kettle caramelization. Some examples may have suggestions of roasty flavors and hints of smoke. Brewers may purposely add a peaty quality in modern examples, but there is no historical precedent for doing so. Hops are mild in this style, and a clean, smooth alcohol quality provides balance to the big sweet malts and adds a dimension of warmth and complexity. Some call this style the barley wine of Scotland.
While the full range of ales are produced, and consumed, in Scotland, the classic names used within Scotland for beer of the type described as "Scotch Ale", are Light, Heavy, and Export, also referred to in "shilling categories" as 60/-, 70/- and 80/- respectively, dating back to 19th century method of invoicing beers according to their strength. The "/-" was the symbol used for "shillings exactly", that is, shillings and zero pence, in the pre-decimal £ British currency, so the names are read as "60 (or 70 or 80) shilling (or bob) ale"
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. Hop flavors and bitterness are low to medium-low, so malt impression should dominate. Diacetyl is low to none, although caramelization may sometimes be mistaken for it. Low to moderate esters and alcohol are usually present. Esters may suggest plums, raisins or dried fruit. The palate is usually full and sweet, but the finish may be sweet to medium-dry (from light use of roasted barley).
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.
Comments: Also known as a “wee heavy.” Fermented at cooler temperatures than most ales, and with lower hopping rates, resulting in clean, intense malt flavors. Well suited to the region of origin, with abundant malt and cool fermentation and aging temperature. Hops, which are not native to Scotland and formerly expensive to import, were kept to a minimum.
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. A small proportion of smoked malt may add depth, though a peaty character (sometimes perceived as earthy or smoky) may also originate from the yeast and native water. Hop presence is minimal, although English varieties are most authentic. Fairly soft water is typical.
Source: Beeradvocate: http://www.beeradvocate.com/beer/style/77/, wikipedia: http://en.wikipedia.org/wiki/Pale_ale#Scotch_ale