1784 was a momentous year. It's when the first analyses of beer gravity and attenuation were published. You could see it as the beginning of modern, scientific brewing.
It's hard now to imagine that brewers once had little idea of the strength of their beers. They knew how much malt they'd put in, which gave them a very general idea. But they had no idea what sort of yield their malt gave them nor how far the wort had attenuated. The hydrometer changed all of that.
In the 1770's, Richardson carried out a series of experiments using the hydrometer to measure worts before and after fermentation. Funny thing is, hydrometers had been knocking around for ages. Distillers had been using them since the 17th century. funny how no-one thought to take one into a brewery.
Here are the results of Richardson's investigations:
A couple of things stand out. First, the erratic attenuation of Strong and Common Ales. Second, the poor attenuation of the Strong Ales. The Porters, averaging around 75% attenuation, look positively modern. You'll note that the Porters are much stronger than their 19th century descendants.
What effect did the hydrometer have on brewing? It made brewers aware of the yield they obtained from their malt. Which in turn led to changes in the selection of materials and brewing techniques. Seeing the better yield from pale malt, brewers soon changed to using it as a base for all beers, including Porter and Stout.
Soon after the publication of Richardson's work hydrometers were in widespread use in larger English breweries. Not really a surprise. Would you want to brew commercially without one?
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