According to this article from Briess: Briess Defining Wort Colors, the type of malt you use directly affects the color of your beer. Using base malts typically contributes yellow to orange tones. Using crystal/caramel malts typically contribute orange to red tones. Using roasted malts typically contribute brown to black tones. With that in mind, and referencing the article, we can safely say that 20 SRM ≠ 20 SRM. That calculated 20 SRM could be a black 20 or a red 20, depending on the type of grains you use to color the wort.
Something that we already do for pH calculation is define malts into categories. Those categories being Base Malts, Specialty Malts, Crystal Malts, and Roasted Malts. Using these existing categories, is it possible to create a more predictable SRM calculation for brewers?
Let’s define those categories in the following way:
Base Malts contribute yellow tones up to light orange tones.
Specialty Malts contribute orange tones up to ruby tones.
Crystal Malts contribute light ruby tones up to red tones, and deep red/brown tones.
Roasted Malts contribute light brown tones up to dark black tones.
The following image depicts these malt categories. The color system used is in CMYK, with only Magenta, Yellow, and Black being used to create these colors. The beginning of each gradient shows the lightest potential, and the end of each gradient shows the darkest potential. These colors are purely estimations that are based on visual comparisons of existing SRM color charts.
The existing SRM calculation uses the following equations.
SRM = 1.4922 x (Batch MCU ^ 0.6859)
Where Batch MCU (malt color unit) = MCU1 + MCU2 + MCU3 … etc
Where MCU = ((ºL * Grain Weight in lbs) ÷ Batch Volume in gallons)
Example for 5 gallons of Irish Stout:
7 lbs of Maris Otter… ((3ºL * 7 lbs) ÷ 5 gal) = 4.20
1 lbs of Roasted Barley… ((550ºL * 1 lbs) ÷ 5 gal) = 110.00
1 lbs of Flaked Barley… ((2ºL * 1 lbs) ÷ 5 gal) = 0.40
4.20 + 110 + 0.40 = 114.60
1.4922 x (114.60 ^ 0.6859) = 38.57 SRM
Extreme unworldly example for argument’s sake:
191 lbs of Maris Otter … (3ºL * 191 lbs) ÷ 5 gal) = 114.60
1.4922 x (114.60 ^ 0.6859) = 38.57 SRM
Obviously the latter example is ridiculous, but it is an extreme example to show that using the existing equation, we can achieve similar SRMs when using an absurd amount of base malt versus using a sensible amount of roasted malt.
Not to say that the current equation isn’t extremely helpful when estimating beer color, because it is. But it’s just that, an estimation. Can we better predict beer color? Is there a new color mode that can be created, similar to CMYK or RGB, that can be used to create a better equation?
Can a YORB color system be created for malts?
Where Y = Yellow, O = Orange, R = Red, and B = Brown/Black.
example of malt categories…
Yellow malts:
Pilsner malts
2-rows/6-rows
Pale Ales
Red Wheat
White Wheat
Flaked Malts, wheat, oat, corn, rice
Oat Malt
Carapils
Orange malts:
Viennas
Munichs
Aromatics
Honey Malt
Melanoidin
Red malts:
Crystal Malts, all colors
Caramel Malts, all colors
DRC
Special B
Extra Special
Brown/Black malts:
Brown Malt
Pale Chocolate
Coffee Malt
Chocolate
Roasted Barley
Black Malt
Each malt is defined in a category that describes its color potential.
Each malt already is defined by a degree lovibond.
MCU would need reworking to factor in each malt’s category.