Beer Varieties: The Origins (Part Three: Colour)
In this series, we are exploring what characterizes the hundreds of styles of beers that are available. While yeast is the most important determinant of beer style, two of the other main ingredients (hops and malt), and how the beer is brewed, among other things, also play a part. It is these factors that create the inherent qualities of the beer, which formulates each category or style. Part Two looked at how gravities and alcohol by volume (ABV.) are calculated. In Part Three we will explore colour; how it is measured, and how the different colours are assigned.
By David Nuttall on Sep. 08, 2016
What colour is beer?
Through much of history, beer was a rather murky, nondescript brownish colour. It wasn’t until the rise in the popularity of lagers and the refinement of dark beers such as stouts and porters, in the mid 1800s, that colour measurement and differentiation became important. To this end, the Lovibond scale (L), also known as degrees lovibond, was introduced by Joseph Lovibond in the 1860s. Originally used to measure gas colours, it was expanded to measure other products such as chemicals, oils, foods and beverages as well. Colour was determined by how closely a sample matched a colour disc of tinted glass when placed in a “Tintometer”. For brewing, Lovibond was used primarily to specify grain colours by preparing a laboratory wort from a sample of the malt and comparing that to the colour discs. This method lasted until 1950, when The Standard Reference Method (SRM) was adopted by the American Society of Brewing Chemists.
What causes beer to be different colours?
The type (colour) of the malt is still the main factor in beer colour, but the intensity and length of the boil also contribute. Common or base malts such as Pilsner or Pale Ale malt will produce a light straw or yellow colour. Caramel malts will create gold to amber beers and specialty dark malts, such as Brown malt and Chocolate malt will produce brown and black beers. Using different malts in combination will derive the other colours between straw and black. In fact specialty malts need only account for only 5-25%, and can be as little as 1%, of the total amount of grain used to achieve a darker colour. Because specialty dark malts are a result of grains being roasted or cooked at high temperatures, they do not have enough enzyme activity (sugars) to work alone in the mash, and must be combined with base malts in order to produce a wort.
Thus, once the types of malts are determined, the resulting colour becomes an important characteristic of style.
How is the colour of beer measured? What is the SRM of a beer?
Today, two scales are now used for colour determination, or more correctly, to measure colour density- the SRM scale used in much of the world and the European Brewery Convention (EBC) scale in Europe. Both are numeric scales that go from low (light colours) to high (dark colours). This is calculated by using a spectrophotometer or photometer to measure the attenuation of a deep blue light at 430 nanometers as it passes through a sample contained in a standard 1 cm by 1 cm cuvette (a square test tube).
How to calculate the SRM of a beer
The formula derived is:
SRM = 12.7 x D x A{430}
where D is the dilution factor (D = 1 for undiluted samples, D = 2 for 1:2 dilution, etc.) and A{430}is the absorbancy at 430 nm in 1 cm.Example: an SRM of 31.75 =12.7 x 1 x 2.5
The wavelength of deep blue light and the multiplier were chosen to make the resultant values of the SRM formula comparable to those in the Lovibond system. The EBC formula is similar, but the unit of colour is 25 times the dilution factor, rather than 12.7. The resultant conversion formula is:
EBC = SRM X 1.969
This results in EBC values commonly being considered about twice the SRM values.
The formula yields numbers that are given names of colours. They start at straw around 2-3 SRM and lead to amber at 6-9 SRM. Light brown begins at about 17 SRM, with black coming in at around 30 SRM. Black has a darker version, called black opaque, represented by over 40 SRM (40+). The main difference between the two kinds of black is that a back light can be seen through lower numbered beers, while opaque black beers will not let much or any of the light shine through.
BJCP 2015 Guidelines for SRM values
Straw 2-3
Yellow 3-4
Gold 5-6
Amber 6-9
Deep amber/light copper 10-14
Copper 14-17
Deep copper/light brown 17-18
Brown 19-22
Dark Brown 22-30
Very Dark Brown 30-35
Black 30+
Black, opaque 40+
As much as 90% of the world’s beer falls into the straw or yellow colour realm, due to the predominance of light lagers being brewed in almost every country. However, since the growth of craft breweries in the past 30 years or so, more beer styles are being explored, and more colours are showing up in pint glasses. There are now more opportunities to enjoy the golden hues of a maibock, the caramel flavours of an amber ale, the bitter fruitiness of a Flanders red, the roasted nuttiness of a fine brown ale, or the dark chocolate/coffee richness of an imperial stout (For a list of beer styles and their colours see Just Beer article: Beer Colours: The SRM Colour Guide for Beer Styles).
In fact, if you add fruit beers or specialty beers that have unusual ingredients to the mix, a beer can be almost any colour at all these days. Fruit beers tend to start as a light coloured beer and once the fruit or syrup is added, its colour changes. Of course, a brewmaster (or pub) could add artificial colouring to any light coloured beer, much the way green beer is created on St. Patrick’s Day.
Beer colour therefore becomes important to even the casual beer drinker. It is the only property of a beer that can be gauged on sight alone. Also, because it’s the malt that produces those colours, certain aromas and flavours become expected from beers of different colours. While most beers fall in the standard straw to black realm, modern brewers now have the ability to make beer literally any colour they so choose. The only restriction is their imagination.
SRM Colour Chart
Want to learn more about Beer?
Go back to school at the ABF Beer School with David Nuttall.