OG is lower than target
TroubleShooting
John “Mick” Barnes • Marcellus, New York asks,
Help! I have been brewing for about 10 years and have just taken the step to all-grain. I have been reading and trying many of the recipes in BYO, and as long as I stay with extracts or partial mash, I am very close to the OGs. But when I do an all-grain batch, I am about ten points below the target OG. I know I can correct this with some DME, but I don’t want to. When you publish recipes, is it assumed that the brewer knows enough to adjust for mash efficiency, or are they already adjusted to some unknown mash efficiency? I run into the same problem with other books and publications.
The recipes published in Brew Your Own and in other magazines and books are indeed formulated with some efficiency in mind. In the case of regular columns, such as “Replicator,” the columnist typically will use his own efficiency factor, based on his system and experience. This is usually between 65 and 68 percent, meaning that a pound of malt will add between 0.65 and 0.68 pounds of extract to the wort. Other recipes are submitted by readers, and it is difficult to know what the brewer had in mind.
I am occasionally asked to review reader recipes. When I review them I begin by checking if the malt (or other sources of extract, when applicable) contributes enough extract to hit the target gravity. In order to do this, some assumption about efficiency must be made, and I personally use between 65 and 68 percent. Sometimes the malt list doesn’t match the original gravity and the amount of the primary extract source (usually some type of pale malt for all-malt brews) needs to be increased in order to improve the odds of hitting the target gravity.
When I use other brewers’ recipes I look at the malts, their relative proportions and the original gravity. I then re-calculate the recipe based on my own brewing system and, to a large extent, ignore some of the finer details of the recipe. I use a certain mash thickness that works for my system, I get a particular yield influenced by my mill and my mash and lauter vessels, I have certain mash profiles that I like, I typically boil wort in a particular fashion and so on. I imagine that most brewers merge a recipe into their standard procedure in a similar way.
It sounds to me that your system consistently has an efficiency less than that used by most homebrew publications when they check the accuracy of recipes. If I were you, I would adjust recipes by focusing on the pale malt (or other primary source of extract). You may find that simply increasing the amount of pale malt by 20 percent over what is listed in the recipe works out. You may also want to examine the coarseness of your malt. Overly coarse grist may be one of the culprits behind your low yield problem and simply using a finer grist may help out considerably. Regardless of how much tweaking and tuning a brewer does to his system, it will never be able to exactly produce 5 gallons of wort at a target original gravity using a recipe based on another brewer’s system unless some modifications are made to the recipe. You could also check out a brewing-calculation software program like ProMash, which makes it easier to adjust base-malt amounts to match target gravities on a given system.
