Brew Pal and Mash Calcs

I'm working on mash calcs for a recipe out of "Brewing Classic Styles," just as a learning exercise. The Brew Pal app for iPhone has been my companion in this exercise. For fun, I've been substituting ingredients, yeast strain and amounts, and seeing the effects on the recipe.

I know Brew Pal is supposed to have stability issues, but by and large it seems to function well for me. The problem is that even when I make *no* substitutions, and enter the BCS recipe as is, with the same assumptions about boil volume, efficiency, and every other variable I can identify, Brew Pal comes out with different OG, FG, and ABV numbers than the recipe in the book. It places my recipe (ordinary bitter) clear out of the style guidelines.

If anyone reading this has experience with Brew Pal and knows of a particular assumption or error built into its calculations that would skew my results, I'd sure like to know the secret. This discrepancy is making me doubt my understanding of the calcs in the book.

I use Brewpal religiously. Double check your efficiency, batch size, estimated loss, and conversion values for each of the grains. I'd bet it's the last one.

By conversion rates do you mean the ppg? The trouble is that I'm not knowledgeable enough to know whether Crystal 120 and Special Roast are 33ppg and light DME is 43ppg, like Brew Pal says. I just took it for granted that the software had the values right.

I'm not sure, but....I think PPG varies from batch to batch of grain. I think that is why PPG in BrewPal is assignable. The values in BCS and the default values in BrewPal might be different. Having said that I wouldn't think the difference would be that significant. I use BrewPal also and have noticed the same thing.

Setting boil size in Brew Pal is hard. There seems to be no place where you can say, "We're starting with 7 gallons in the boil." You have to engineer it upwards from batch size, adjust for boil off rate, trub loss etc.

Question: what is the difference between "trub loss" (found under boil settings) and "system loss" (found under mash/sparge settings)? As I type the question, the answer seems obvious, but I'd still appreciate an explanation from someone else. I have both settings set for .5 gallons, but since I will be steeping my specialty grains instead of mashing, I wondered if "system loss" applies to me, or should be set to zero.

I agree that the ppg doesn't seem like it will account for the gravity and ABV surge I see in Brew Pal's calcs. Brew Pal's default for light LME is 34 ppg; hunting through "Brewing Classic Styles" (not in my bitter recipe) I saw one statement that light LME is usually 36 ppg. When I put that higher value into Brew Pal, hoping to true the calcs to those in the book, it pushes the gravity readings even higher than they were previously.

Although I'm comfortable entering the most fundamental aspects of a recipe into Brew Pal, like setting the grain bill and choosing a yeast, I think I must misunderstand some of Brew Pal's more complicated settings. For a long time I couldn't even FIND some of those default settings, since there's no help file. So, I wasn't able to understand how they were impacting the calcs. Any leads you knowledgeable people can offer me would be appreciated.

I've always assumed that system loss refers to liquid left in the tun after mash/sparge that cannot be collected, or liquid left in transfer lines, etc.. I agree that many of the functions are hidden within BrewPal, but I'm slowly ferreting them out the more I use it and the more I learn about the brewing process. Sorry I can't be more help. I think there is a thread on BrewPal through which you could contact the designer.

i've recently been playing around more and more with brewpal and have found it has many more options and flexibility then people realize. my brewing partner and I have been using beeralchemy for mac and keep coming back to brewpal for the sheer ease and consistency of operation...interface is extremely user friendly compared to most

few things..

its took us a while to input what our systems efficiencies are. once we were able to calculate it ( boil off...trub loss) the results on comparison to what the software said were much more aligned.

i recommend taking a closer look at your efficiency...your trub loss, your boil off..and adjust them in the software to match your system. the software is great when you already know what your system is capable of

I know nothing about Brewpal, but I understand that the recipes were initially developed using Promash, and then converted to extract, and the extract potential for LME is assumed to be 36PPG and DME is assumed to be 42ppg (The Promash defaults are 37 ppg for LME and 46 PPG for DME.)
Plugging the Ordinary Bitter recipe as published into Promash, and adjusting the extract potential for LME from 37ppg to 36ppg gives an estimated OG of 1.044 for a 5.5g batch (which is well outside the guidelines max of 1.040).
Going to the AG option at 70% efficiency yields an OG of 1.042 if the extract potential of British pale malt is 38 PPG (which is typical of British pale malt) or 1.040 if the extrract potential of the malt is assumed to be 36 PPG (which is typical of American pale malt).
To achieve an OG of 1.038 (as specified in the book) using LME at 36 PPG, with Crystal 120 and Special Roast, you need to reduce the LME from 6.1 lb to 5.4 lb

Hope this helps.

-a.

Thanks for your replies, Gbrown and A. Since the date of my post, I've become much more comfortable with BrewPal. Asking my LHBS for the yield from the DME they sell was a big help, because I was able to edit the value in the software and start to see the gravity calcs play out as expected. There's still much I don't understand about the software, but that's due more than anything to my experience as a brewer! (I'm doing my first AG batch this Father's Day.) The fun is in brewing, brewing again, and becoming more and more comfortable with the resources at your disposal.

Happy brewing!