Essay: The difference between ale and beer
Michael Hall in his article about Beer History continues that in 15th-16th century beer brewing art stepped out from being a family practice and transformed into a trade. As breweries and monasteries started dealing in beers, mass consumption of beer started. The differentiation between ale and beer was done on the basis of hops.
The un-hopped beer came to be known as ale while the hopped one was known as beer. In 1400s England imported hopped beer from Netherlands, and later they started planting hops natively. By 16th century however ale became a common name for strong beer and then both ale and beer were started being hopped. In the year 1516, the German King, William 1V, Duke of Bavaria implemented and adapted a purity regulation system. This act was added to the German unification in 1987, and is still applicable in modern beer brewing. What now we call as ales, was beer at that time. However when in 16th century beer was kept for storage in cold caves, Lages was discovered incidentally and from then on superseded ales in matter of its volume.