We use a wide variety of words to talk about beer color — words such as white, pale, straw, blonde, beige, golden, yellow, honey-like, latte, orange, bronze, brown, mocha, caramel, chocolate, black, and many more. Yet even this list is inadequate to describe traditional beer styles. Beyond that we also have fruit beers, cloudy beers, color-dyed beers, clear beers and other variations with color well outside the standard beer color scale. In this article we’ll explore a bit of history on beer color, how the current SRM and EBC color scales evolved, and also how beer gets its color. I’ll close with some thoughts on estimating color, and the innovative use of color in beer — frontiers we are still exploring today.
History of Beer Color
For much of recorded history, dark or darker beers with colors varying from that of a brown ale to a dark stout dominated brewing. This is because malts were kilned primarily over wood fires, and so they had a smoky character and dark color that would be closer to a smoked modern brown malt than pale or Pilsner malt.
Around 1642, the first pale malts were made in small quantities by kilning them over coke instead of wood. (Coke is a fuel usually derived from coal that has few impurities and a high carbon content.) However it would be another 150 years before these malts were mass produced and became affordable. Most of the modern light beer styles we enjoy today such as bitters, most lagers, Pilsners, and IPAs were introduced in the 1800s after pale and Pilsner malt entered mass production.
Coincident with the introduction of lighter malts was a similar revolution in the production of glassware. Where clear glassware was once hideously expensive and owned only by royalty and the very rich, the industrial revolution made glassware affordable. Suddenly drinkers could see the beer they enjoyed.
The combination of clean pale and Pilsner malts and affordable glassware led to a revolution in brewing as well as dramatic change in drinking habits as consumers abandoned their smoky dark traditional beers and started consuming lighter-colored continental and English styles in the 1850s.
So in the mid-19th century, the palette of beer expanded from “dark and darker” to the array of colors modern beer drinkers enjoy. As this happened, the interest in measuring the color of beer also increased.
The first widely used system for measuring beer color was invented by J.W. Lovibond in 1873, a system to which he gave his name. Even today, Lovibond is used to characterize the color of most malts in the US. The Lovibond system originally used colored slides, each representing a color in “degrees Lovibond.” Later, beer color was often graded by comparing beer against glass standards.
Over time the limitations of Lovibond became apparent. Variations in lighting, as well as a person’s individual color perception could significantly affect the judged color of a sample. By the mid-20th century, light spectrophotometer technology was developed. In 1950 the American Society of Brewing Chemists adopted the Standard Reference Method (SRM) color system. Separately the Europeans developed another visual system called the European Brewing Convention (EBC). It originally used visual comparison, but some 25 years later changed to use a spectrophotometer in a slightly different way than SRM.
The SRM color of beer is measured using a 1⁄2-inch glass cuvette and a spectrophotometer at a light wavelength of 430nm. The SRM color is defined as 10 times the amount of absorbance, which is measured on a logarithmic scale. The SRM color is approximately equal to the old lovibond scale in most cases, which made the transition from Lovibond to SRM easy for brewers.
The other common method, called the European Brewing Convention (EBC), is measured at the same wavelength but in a smaller 1-cm cuvette. Most modern spectrophotometers use a 1-cm cuvette and simply scale the result differently to measure in EBC or SRM. In practice, the EBC color is approximately 1.97 times the SRM color (EBC = 1.97 * SRM) for light beers, though it diverges slightly to a more complex formula when measuring darker beers.
Limitations of SRM and EBC for Homebrewers
Whether you use SRM or EBC measurement methods, you need to understand that both measures are a crude attempt to represent a wide spectrum of colors as a single number. Anyone who took a grade school art class knows that there are three primary colors: Red, blue, and green, and the combination of those primary colors ultimately give us the spectrum of colors we see. All colors, therefore, have three components to them: Red, blue, and green. To that we could also add a fourth component, which is transparency (or opacity), as our beers have varying degree of transparency as well. Two beers of identical color shade could appear differently if one was more opaque than another.
The SRM and EBC scales attempt to compress the red, green, blue and opacity information in the actual color into a single number. As a result they will often not capture the exact shade and color of the beer. While this works for many beers, it will fail to capture the decidedly red hue of an Irish red ale, the cloudiness of a New England IPA or red/purple you may find in a raspberry stout made with real raspberries.
Finally, SRM and EBC measurements are done at a single wavelength of light — 430nm. This 430nm light is on the blue end of the color scale as your eye sees it and not surprisingly does a poor job of capturing shades of reds, yellows and greens. Your eyes cover a wide spectrum from about 400-800nm, and also your brain automatically compensates for the “temperature” or warmth of your light source. Changing the temperature of your lighting from “daylight” to “soft white” indoor or fluorescent lights will change how you perceive the beer color. At best the SRM or EBC number is going to be a good estimate of the color of beer as you see it, and in some cases may not represent the true color of your beer.
Color Measurement for Homebrewers
If you don’t happen to have a spectrophotometer laying around the house, there are good alternatives if you want to measure the color of your own beer. The simplest method is to use a calibrated color reference card such as the Beer Judge Certification Program (BJCP) color guide (downloadable at BJCP.org) to do a visual comparison against your beer. This color guide requires a 5cm deep path (of beer) in daylight with a white background, and the beer color is compared against the color guide. For accuracy, I also recommend purchasing an actual calibrated color card, as the one you print on your inkjet printer may not render the colors 100% accurately.
Other methods include comparing your beer color against commercial beer samples of known color. Ray Daniels, in his book Designing Great Beer, describes this method in some detail, though of course it requires keeping several reference commercial beers on hand for color comparison. Overall I prefer using a color reference card.
The Source of Color
Beer derives its color primarily from the malts, though some adjuncts such as fruit, spices or additives can contribute color in certain specialty beers. The color of malt is developed in the malting and roasting process by two chemical reactions: The Maillard reaction and carmelization.
The Maillard Reaction
The Maillard reaction was first documented by French scientist Louis-Camille Maillard in 1912. It is often called the “browning” reaction as it is the chemical reaction that makes the crust on your bread brown, sears your steaks, and toasts your marshmallows. It is a form of non-enzymatic browning that typically occurs between 140–165 °F (60–74 °C). At higher temperatures, carmelization tends to dominate.
The Maillard reaction is a chemical reaction between amino acids and reducing sugars such as glucose. Both are present in grains that are malted. The reaction can generate a wide variety of flavor and aroma compounds depending on the malt, and also darkens the color of malt. Much as with toasted bread or grilled steak, these flavors enhance the flavor profile of the malt. The elevated temperature range used to kiln most pale malts is strongly associated with this reaction, though the Maillard reaction can take place slowly even at room temperature, which is why malt extracts often darken as they age. Maillard reactions can also occur during mashing and even during the boil.
The second chemical process that drives malt color is carmelization. Unlike the Maillard reaction, carmelization is a thermochemical decomposition that takes place in the presence of high temperatures and oxygen. Basically you heat sugar molecules until they fall apart. The resulting compounds include many aromatic and flavor compounds including diacetyl (buttery), ethyl acetate (fruity/esters) and furans. It also darkens the malt. Carmelization kicks in at higher temperatures, and is a major player in dark roasted malts, caramel malts and dark colored malts.
The Malting Process
A process called malting turns raw barley into the malted barley we use to brew beer. The malting process involves wetting the raw grains enough so they actually germinate and begin growing - turning the seed into a tiny seedling if you will. However the seed only sprouts and grows for a very short time as the growth process is cut short by drying and kilning the malt with hot dry air. These malts are light in color as they are kilned at low temperature primarily to dry the malt out. Pilsner, pale, and Munich malts are kilned at lower temperatures where the Maillard reaction dominates, which is why these malts tend to create flavors like toast, biscuits, cookies, bread, or malty.
Some malts are also roasted at high temperature to create specialty malts such as roasted, chocolate or caramel malts. Roasting these malts results in buttery and fruity flavors at the low temperature end or burnt coffee, burnt marshmallow, and strong roast flavors at the high end. This carmelization also produces the dark colors we associate with dark malts.
Because both the Maillard and carmelization reactions can continue during the brewing process, the process of making beer does actually impact the color of the final product. The impact of mashing and boiling is usually included in when we estimate the color but unusual variations such as a very long mash or boil, or extract or grains carmelizing on the bottom of a mash or boil kettle can create
darker beer than intended. This is usually not an issue but it is something to be aware of if you direct heat your mash tun or have carmelization in the boil.
Pale-colored malt extracts represent another interesting case. Malt extract for extract brewing is made by first mashing and lautering malted grains to produce wort using the same process as an all-grain brewer would use. However, this wort is then boiled to concentrate it into a thick syrup. The boil is often done under a vacuum (at reduced pressure) to lower the boiling point and also reduce the energy used.
When the wort is boiled at a reduced temperature for an extended period to concentrate it into extract, the Maillard and carmelization reactions again kick in. At the temperatures used, the Maillard reaction tends to dominate. As a result our lovely pale color wort is often darkened considerably when concentrated into malt extract. This is why malt extracts, even those made from light colored Pilsner malts tend to be much darker than a comparable all-grain wort. It also explains why it is hard to create very light colored beers like Kölsch using malt extract.
Concentrated malt extract is also subject to the Maillard reaction as it ages on the shelf, due to the very high sugar concentration and acidity of the malt extract. So even at room temperature, malt extracts will tend to darken with age, which is why many extract brewers insist on using the freshest possible malt extract. Storing your malt extract in a refrigerator will also slow the Maillard reaction, and help it retain its original color.
You can estimate the color of your beer directly from the grain bill using either computer software, an online tool, or by directly calculating it. Most modern software uses the Morey equation developed by Dan Morey back in the mid 1990s and first published as a Brewing Techniques article. The Morey Equation gives you a fairly accurate color estimate in SRM units.
The Morey equation calculation starts by totaling up what is known as the Malt Color Units (MCUs) for all of the grains in your grain bill.
MCUs = Sum_of (Grain_Weight x Grain_Color) / Volume_Wort
where the grain weights are in pounds, grain colors in lovibond, and volume of wort is in gallons. You sum all of the (Grain_Weight x Grain_Color) terms up for each of the grains in the grain bill first, then divide the total by the volume of wort in gallons. This lets you estimate the color in the total grain bill.
MCU actually provides a good estimate of beer color for lighter color beers, but starts to diverge from the SRM scale as the beer color exceeds about 7 SRM. This is because light absorbance is logarithmic and not a linear relationship. So to get an accurate color estimate for all beers we need to take the MCU number above and apply the Morey equation to it:
SRM_color = 1.4922 * (MCU ^ 0.6859)
Where the “^” symbol is simply “raised to the power of”. This equation provides an excellent estimate of beer color from 1-50 SRM, and honestly colors beyond 50 SRM appear simply as black to the human eye.
Innovative Use of Color
The Morey estimate above really applies only to traditional beers made with traditional ingredients and methods. This does not mean you can’t make beer just about any color you like. It is common, for instance to add some green food coloring on St Patrick’s day to make green beer. The same technique could turn your ale blood red or just about any other color you like.
Fruits obviously have a large impact on color. Cherry lambic is red, while the raspberry version is decidedly purple. I enjoy adding berries and fruits with acidity and tannins like berries and currants to my beer as these hold up well in fermentation, provide structure to the beer and also add a distinctive color.
You can also play with the opacity of your beer. Traditional hefeweizen is of course cloudy from the yeast left in suspension. The recent New England IPA craze has been turning the tradition of beer clarity on its head by creating beers that are intentionally hazy. Some time back there was a “clear beer” fad with mass-produced beers like Zima. Another interesting concept some homebrewers have explored is creating a beer that tastes like a dark porter or stout but is pale in color. It’s tough to do but certainly an interesting beer to sample when it’s done!
These are just a few examples, but the point is that the color of your beer need not be limited by your ingredients, and you can create just about any color you like — even colors well beyond the traditional SRM/EBC scales.
Color in Perspective
The color of beer has a rich history, and the SRM and EBC scales along with the Morey equation do a reasonable job of providing us with an idea of the color of beer. However, it is also critical to understand the limitations of the SRM/EBC system, and also colors and opacity that it simply may not capture. I hope this article helped you understand where beer color comes from, how it changes during the brewing process and also gave you a few ideas of how you can play with color to create unique beers.