Porters of the late 1700's were quite strong compared to todays standards, easily surpassing 7% alcohol by volume. Some brewers made a stronger, more robust version, to be shipped across the North Sea, dubbed a Baltic Porter. In general, the styles dark brown color covered up cloudiness and the smoky/roasted brown malts and bitter tastes masked brewing imperfections. The addition of stale ale also lent a pleasant acidic flavor to the style, which made it quite popular. These issues were quite important given that most breweries were getting away from pub brewing and opening up breweries that could ship beer across the world.
Average alcohol by volume (abv) range: 7.0-10.0% --BeerAdvocate
