The Auld Alliance

Although Scotland harbours a population only one tenth the size of England, it has nurtured a unique brewing culture for much of its history. Like their neighbours to the south, Scottish brewers were active in exporting beer around the globe during the eighteenth and nineteenth centuries. They also produced a broad variety of styles including those usually associated with England and Ireland and they were the first British brewers to make lagers.
 
Agriculture still occupies three-quarters of the land in Scotland and barley remains a major crop. Barley produced in the north of Scotland most often becomes Scotch whiskey while that grown in the south is better suited to the making of beer. As a result of these patterns, barley has been readily accessible to Scottish brewers throughout their history.
In contrast to barley, hops refuse to flourish in Scotland. Long after the English had conceded to use hops, the Scots continued to prefer other bittering substances. A variety of products were used instead, including "ginger, pepper, spices and aromatic herbs."
A further encouragement of these pressures came when Scotland and England joined in 1707. The Treaty of Union that joined Scotland and England specifically excluded Scotland from a substantial malt excise tax, thus sustaining the malt-oriented view of the Scottish brewers.

As a result of these influences, we today recognize four styles of beer that hail from Scotland.

Three are called Scottish ales and range in gravity from 1.030 to 1.050. These three are distinguished by strength, as Light (OG 1.030-1.035), Heavy (OG 1.035-1.040) and Export OG 1.040-1.050).
The fourth style, known as a Scotch ale, is much higher in gravity, ranging from 1.072 to 1.085. It is often called "strong Scotch ale," or by its common nick-name of "Wee Heavy."

Scottish ales are often labelled according to an old price-based system of identification. The Light, Heavy and Export are known as 60/-, 70/- and 80/- shilling ales respectively. Wee Heavies are commonly called 90/- or even 120/- shilling ale.