How does BTP calculate SRM of recipes?

[TCBrewguy]

I've been comparing the SRM of a pale ale recipe between apps like BTP, ProMash, BeerSmith, Beer Alchemy and the hbd.org/recipator. It seems like BTP calculates a darker SRM than any of these other apps. I've used BTP since the first beta version and have never questioned this calculation before, but now I'm wondering how the app calculates color and why there would be a disparity between apps. BTP calculates an SRM of 12.4 for a recipe that all of the other aforementioned apps calculated at about 9. I made sure that all other variables (e.g., pre- & post-boil volumes, efficiency, etc.) were as equal as possible while plugging in this recipe.

edit: I also noticed that ProMash allows users to choose different color algorithms. One such algorithm is the "Morey" color formula. BeerSmith exclusively uses Morey's power equation. Here is a link to a Brewing Techniques excerpt where Dan Morey briefly discusses his color formula. From brief discussions with other brewers who use brewing software, it sounds as though the Morey formula is the most common one applied these days.

Would you guys be open to adding a color formula feature to BTP in the future? Maybe allowing users to choose between Daniels', Mosher's and Morey's formulas?

[TCBrewguy]

Here's an example of why I think allowing users to choose their color formula would be useful. The main window shows a recipe with an SRM of 11.8. Using the Morey Color Formula, the SRM is 8.6, reflected in the SRM calculator window. To me, that's enough of a difference (especially with SRM's > 10) to warrant the option.

[jeff]

Currently BTP uses Noonan's data for generating the formula.

[TCBrewguy]

Currently BTP uses Noonan's data for generating the formula.

Any chance that in future releases there will be a color formula choices (Noonan, Daniels, Mosher, Morey, Fowler )?

[jeff]

Any chance that in future releases there will be a color formula choices (Noonan, Daniels, Mosher, Morey, Fowler )?

Posting those formulas here might increase the likelyhood

[TCBrewguy]

Any chance that in future releases there will be a color formula choices (Noonan, Daniels, Mosher, Morey, Fowler )?

Posting those formulas here might increase the likelyhood

Gotcha! Well, here they are:

Morey's Formula
SRM = 1.4922 [(MCU) ^ 0.6859]

Daniels' Formula
SRM = (MCU * 0.2) + 8.4

Mosher's Formula
SRM = (MCU * 0.3) + 4.7

where MCU (malt color units) is the weight of the ingredient in pounds times its color rating (in degrees L) divided by batch size, i.e., 'final volume' in BeerTools Pro (in gallons).

I sourced Morey's formula from a Brewing Techniques post he made. I sourced Daniels' and Mosher's Formulae from the Atenveldt Brewers Guild Brewer's Handbook, pp. 30-31.

[jeff]

I believe I can find Daniels' formula in Designing Great Beers when I get home. I'll try to get my hands on Mosher's too.

Thanks man!

[TCBrewguy]

I believe I can find Daniels' formula in Designing Great Beers when I get home. I'll try to get my hands on Mosher's too.

Thanks man!

No prob! See above...I found all of em.

In addition to the Atenveldt Brewer's Guild Handbook, Daniels' and Mosher's Formulae can both be found in the publication Brewing Techniques, Vol. 3 #6 - November/December 1995, in an article entitled "Beer Color Demystified - Part III" if you care to double check the above.

[TCBrewguy]

I know you guys are pretty busy, Jeff, but I was just wondering if a color formula selection feature would be part of the next release? Or possibly 1.1? I can do the Morey formula by hand in the meantime.

[rrosa]

I am surprised to see that none of the formulas above take the boiling time into account. That could make a significant difference, couldn't it?

[TCBrewguy]

I am surprised to see that none of the formulas above take the boiling time into account. That could make a significant difference, couldn't it?

Ray Daniels discusses that very point in his book Designing Great Beers. However, he comes to the conclusion that given the huge amount of differences between individual homebrewing systems/procedures, there isn't a formula that can truly express the difference that boiling time/kettle caramelization would make. So, the color formulas that I posted above (which are used by many other brewing apps including ProMash) don't take boiling time into account. FWIW, beers brewed on my system seem to come out lighter than what BTP projects using the Noonan formula. My beers are closer to what the Morey formula projects. This is why I would like the option to choose between color formulas.

[rrosa]

That makes sense.

I have to admit I didn't trust the color prediction of BTP. Two dark beers that I brewed recently came out darker than what BTP predicted, but I boiled them for two hours on purpose (a dubbel and a barley wine). The Stout was boiled for 75 min but it is too dark to tell any difference. I have to check the lighter Pale Ale.

[TCBrewguy]

That makes sense.

I have to admit I didn't trust the color prediction of BTP. Two dark beers that I brewed recently came out darker than what BTP predicted, but I boiled them for two hours on purpose (a dubbel and a barley wine). The Stout was boiled for 75 min but it is too dark to tell any difference. I have to check the lighter Pale Ale.

Precisely why BTP could use a color formula selection feature!

[jawbox]

I agree, we get the choice with hop utilization, we should have be able to select a method of calculating color that will match our individual systems the best.

[harten74]

Bump... This would be very useful. Are there plans to add this feature in a future update?