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Brews & Views Bulletin Board Service * Brews and Views Archive 2004 * January 12, 2004 * Help with Receipe Colour formulas? < Previous Next >

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Fredrik (
Posted on Tuesday, December 30, 2003 - 01:14 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

I'm come to the colour part of the receipe formulas and I'm looking for the formulas used for colour calculations from a receipe.

First I fail to find the definition of the SRM values of malt. I know it's a measure of absorbance at a certain wavelenght, but what's the size of the container, and what strenght of the extract is used for producing the lot numbers?

Does anyone have a refercen to any forumlas?

I've been extrapolating some tables I found and it seems

the Colour vs extrakt% is fairly accurately a

Colour = A * Extract^B

Where A and B are constants.

I found that "B" seems to be almost independent of the malt.

"A" however seems to depend in a nontrivial way on the malt colour. Only approximately proportional to the square root of the malt SRM values?

What formulas are promash using? There must be some offical formula right?

I searched the net but doesn't fint any formulas.
All you guys that doesn't use promas and use spreadsheets, what formulas do you use?


Bill Pierce (
Posted on Tuesday, December 30, 2003 - 02:04 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

Randy Mosher had a very good article on beer color in the September-October 2003 issue of Zymurgy. It provides much of the information you are seeking. The chapter on color in Ray Daniels' Designing Great Beers is also a good reference.

Fredrik (
Posted on Tuesday, December 30, 2003 - 03:03 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

Thanks Bill! maybe I should get that book of Ray Daniels! My LBHS has it in stock. However they are closed for the holidays and I am eager to finish the spreadsheet :)

Any chance I can buy zumurgy articles online? or do they only come in papercopies?


Bill Pierce (
Posted on Tuesday, December 30, 2003 - 03:21 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

Zymurgy articles are not available online. Perhaps you could find someone to copy it for you. I don't have a flatbed scanner. If you can't find it elsewhere I'll copy the article and scan it, then e-mail to you.

Jeffrey Donovan (
Posted on Tuesday, December 30, 2003 - 03:52 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

From the ProMash Help....thought it might shed a bit more light on the subject......

ProMash produces color swatches based upon a calculated SRM color value which is determined from the color values of the malts which make up the grist (Details of formulas ProMash can use for calculating color). As the color values of the various malts are determined with a special laboratory mash procedure which is quite different from typical mashing procedures used in actual brewing, as there is no accurate way to account for the color changing effects of inordinately short or long boils, abnormal water loss (or gain from dilution) in the copper, as the effects of fermentation on color change cannot be accurately predicted and especially as wort and beer do not follow Beer's law (which says that total light absorption at a particular wavelength is proportional to the concentration of dissolved material) the calculated SRM values should be viewed as approximations. Furthermore, the ASBC's Standard Reference Method (SRM) value is, by itself, insufficient to specify beer color. SRM measurement requires that the beer being measured have "average" spectral absorption characteristics. Given that this requirement is satisfied the SRM color is 10 times the absorbance of one-half inch of beer at 430 nm. To calculate color from the SRM value and present the color on the screen of your computer requires several assumptions. These are that the beer does have the average spectral characteristics required for a valid SRM computation, that the beer is being viewed by transmitted light which has the color characteristics of "Illuminant C" (which resemble mid day northern light), that the thickness of the beer being viewed is 5 cm (the same assumption as is required by the Davidson Guide based on the diameter of the base of the typical cup used in homebrew competitions) and that the user's computer monitor is "profiled" to accurately present the calculated colors to the viewer.

As most beers (with the exceptions of fruit beers) have nominally the same spectral characteristics, as the eye compensates for differences in illuminant spectral characteristics to some extent and as most computer monitors are at least approximately calibrated, the ProMash color swatches can be used to roughly compare the colors of beers provided the 5 cm rule is not violated. Beer thickness has a profound effect on the perceived color of beer. One can easily see this by looking at a Pilsner served in the traditional conical glass. At the top, where the light path through the beer is greatest, the beer will appear much redder than near the stem where the path is shortest. For example, consider a beer 5 cm of which passes 10% of blue light and 90% of red light so the ratio of red to blue light exiting will be 9:1. Doubling the path to 10 cm results is 10% of 10% of the blue light or 1% passing though and 90% of 90%, or 81% of the red light so now the red-blue ratio is 81:1 and the beer appears much redder.

Thus to compare beers to the ProMash color swatches and especially to each other it is important to use a container that is close to 5 cm (2 inches) in diameter. If possible use the light from a north facing window and try to do the comparisons around noon. Even so, do not be surprised if the colors seen on the screen do not match exactly to the beer in your hand. Concentrate on the lightness or darkness of the beer rather than on its hue.

Fredrik (
Posted on Tuesday, December 30, 2003 - 04:07 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

I tried a few searches again, I found some further reading and I'm going to play some more, but to determine the constants I need to know the definitions... I found someone claming that the lot data are measure on 1.0462 extract (ie they make an extract and dilute it to 1.0462 without boiling). However this was said not to apply to dark grains, so the question is what math they use when scaling back and forth when diluting the samples, as it's not linear. I'll give it one more try, otherwise I may look for a copy of that article. Thanks Bill.


Fredrik (
Posted on Tuesday, December 30, 2003 - 04:26 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

Thanks Jeffrey for the additions. I see that if I want to know the spectrum it's complex and the data available isn't enough. But for my first receipe sheet I'm happy if I can predict the standard 430nm values roughly properly :)

Btw, is the colour extraction yeild assumed to correlate to the normal extract/grain yield? That is suppose I have 70% mash/lauter yield, do I have also 70% yield of total colour contribution or is the colour yield higher?


Drew Avis (
Posted on Tuesday, December 30, 2003 - 05:25 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

Fredrik, have a look at:

Especially the last link:

This outlines the "Morey" formula for estimating beer colour based on the malt lovibond ratings. StrangeBrew uses this formula, and I think Promash does too (but Jeffrey would have to confirm this).

As you must have noticed based on your question, this formula does *not* account for efficiency / extract. So if you adjust your brewhouse efficiency down to 10% or up to 90%, you get the same estimated colour.

Now, it seems that *most* colour is extracted during the first runnings, especially with darker roast malts, so perhaps the approach that efficiency doesn't affect colour is "close enough" that it works at the efficiencies most homebrewers experience (65%-80%). However, if you were brewing with very low efficiency (say for a barleywine) you might want to compensate your colour estimate slightly.

Good luck w/ your research.

Fredrik (
Posted on Tuesday, December 30, 2003 - 07:41 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

Thanks Chris! the forumla in the second link from Dan Morey formulas is pretty much on the spot what I arrived at as well extrapolating a table I found. cool :)

The exponent 0.685 is exactly what I found from extrapolations. The variations I found in the square root is explained in this forumla! ^0.685 rather than ^0.5!

So are you saying that the colour yield is always high? Suppose I regulate the colour yield in with the extract effiency number, would that mean I underestimate the colour?


Fredrik (
Posted on Tuesday, December 30, 2003 - 07:43 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

I mean thanks Drew, not Chris :)


Drew Avis (
Posted on Tuesday, December 30, 2003 - 08:24 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

Bob, I mean Frederik, I'm saying that efficiency seems to have less of an effect on colour extraction than sugar/fermentable extraction - but there must be *some* effect, because even the last runnings have a bit of colour. No forumula I've seen accounts for this, though. You'd need to do some actual testing to come up with a model.

Fredrik (
Posted on Tuesday, December 30, 2003 - 10:23 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

I think I got it now! It seems most tables doesn't account for the yield at all. It seems they assume 100% colour yield and just go for the amount of grains rather than amount of extract. It clearly can't be truly correct, but if that's the standard procedure I'll use it for now, the colour isn't the most important thing of the beer anyway. If I can do ballpark estimates for the beer colour I think it's enough. Extra light, golden, middle dark, very dark och black, that's all I need to know for now I think, anything else will be left for future projects.


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