Plato scale

When drinking beer, there are many factors to be considered. Principal among them are bitterness, the variety of flavours present in the beverage, along with their intensity, alcohol content, and colour. Standards for those characteristics allow a more objective and uniform determination to be made on the overall qualities of any beer.

"Degrees Lovibond" or "°L" scale is a measure of the colour of a substance, usually beer, whiskey, or sugar solutions. The determination of the degrees lovibond takes place by comparing the colour of the substance to a series of amber to brown glass slides, usually by a colorimeter. The scale was devised by Joseph Williams Lovibond. The Standard Reference Method (SRM) and European Brewery Convention (EBC) methods have largely replaced it, with the SRM giving results approximately equal to the °L.

The Standard Reference Method or SRM is a system modern brewers use to measure colour intensity, roughly darkness (but see Tristimulus Colour below), of a beer or wort. The method involves the use of a spectrophotometer or photometer to measure the attenuation of light of a particular wavelength, 430 nanometres, as it passes through a sample contained in a cuvette located in the light path of the instrument.

The EBC convention also measures beer and wort colour, as well as quantifying turbidity (also known as haze) in beer.

Beer strength is the alcohol content measured by volume expressed as a percentage, that is to say, the number of millilitres of absolute alcohol in 100 ml of beer.

The most accurate method of determining the strength of a beer would be to take a quantity of beer and distill off a spirit that contains all of the alcohol that was in the beer. The alcohol content of the spirit can then be measured using a hydrometer and tables of density of alcohol and water mixtures. A simple calculation would then yield the strength of the beer. This method is accurate, but is time, energy and beer consuming.

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