Sunday, March 10, 2013

SRM / Lovibond / EBC Values

I started looking at SRM recently, after doing some research on Westvleteren 12, which according to notable sources has an SRM 40. This number seemed off the mark to me, so I knew I needed to do a bit of research because I want to brew a credible clone of the Westy 12.

Keeping track of what color value means what is complicated a bit because there are three different scales for determining the color of a beer: SRM, Lovibond and EBC. SRM and Lovibond are essentially the same for the values that can be discriminated by the human eye:

°L = (SRM + 0.6) / 1.35
For example, with an SRM of 6, the Lovibond value would be 4.88, so the difference is nearly indistinguishable, and I think most people treat them as being the same. Looking at beer in a glass, I don't think I could spot one degree of difference without some reference system. Here's an example:

SRM   Color  

EBC is roughly double SRM, but not quite. Why should any part of this be simple?

EBC = SRM x 1.97
SRM = EBC x 0.508
And just to keep things more interesting, the Lovibond scale is mostly used to express the potential color for dry ingredients such as malts and sugars, while SRM and EBC are used to express the color of liquids.

So, back to the problem at hand, the color of Westvleteren 12. To put things in perspective, here is a scale that represents the colors for various style of beer. (Yes, I know that what I can show on a webpage is only a vague approximation because the perceived color depends on the angle of the light, the angle of the view, and the thickness of the sample, so bear with me.) If Westy 12 really does come in at SRM 40, it's at the end of the scale, and is the same darkness as Imperial Stout.

SRM EBC Example Styles   Color  
2 4 Pale Lager, Pilsener
3 6 Maibock, Blonde Ale
4 8 Weissbier
6 12 American Pale Ale, India Pale Ale  
8 16 Saison
10 20 English Bitter, ESB
13 26 Biere de Garde, Double IPA
17 33 Vienna lager, Märzen, Amber Ale
20 39 Brown Ale, Dunkelweizen
24 47 Doppelbock, Porter
29 57 Stout
35 69 Foreign Stout, Baltic Porter
40+ 79+ Imperial Stout

With all this in mind, 40 seems way too dark. To settle it once and for all, I needed to open a bottle of Westy 12. This is the kind of research I need to do more often. Looking at a fresh pour, it looks pretty dark, but the head isn't as dark as I would expect for RIS:

And when I shine a flashlight from the back, it's clearly not as dark as RIS:

Finally, as I expected, pouring it into a smaller glass has a significant effect on the color perception. There is also a bit of sediment from the bottom of the bottle which gives the light something more to reflect off.

I think I'll be shooting for an SRM around 25 or 26 when I brew my Westvleteren 12 clone.

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