Advice to hombrewers when the batch specific gravity needs adjustment
As a homebrewer, we’ve all been there. That moment during your brew day when you realize something went wrong and you’re off track. For me, confirmation of that fact usually occurs when I take my first gravity read following the mash at the pre-boil stage of my brew day. I usually know its coming; I missed my target mash temp, my pH was a little off, I got distracted and missed a small step in my process. Sometimes it’s completely unexpected too. Now I find myself staring with dread at that pre-boil gravity number, and its confirmed…I messed up. What to do? Dump it all and start over? That’s a waste of money and time, which most of us can’t afford in our busy lives. It’s time to signal for a relief pitcher! Well that’s me, put me in coach!

Common reasons we miss our gravity

As I said earlier, I usually have a sense that I’ve messed up something in my brewing plans. Common sources for missing your target gravity include:

• Grain Milling – I’ve found it’s always good to check your grain crush before starting the mash. I’ve experienced times when I hadn’t noticed the gap on my home mill had slipped and my crush was poor leading to poor extraction. The same goes for grain from your local homebrew store. Be familiar with what your desired crush should look like and then check it when milling at your local shop.
• Mashing Temperatures – This source has more to do with the fermentabilty of your wort, attenuation and your final gravity. As a general rule, if your mash temp is lower than expected, you can expect your wort to attenuate more than expected. This means not only a lower than expected final gravity, but also a drier beer. If your mash temperature is hotter than planned, your wort will attenuate less and have more body and may be sweeter.
• Sparging speed and temperature – Sparging too quickly or with the wrong temperature, or using the wrong volume can drive a gravity miss.
• Volumes – Failing to carefully measure your volumes at each step of your brew day is very important. For example, a 10% increase in final wort volume can lead to a 10% miss in Original Gravity (OG). I learned this lesson the hard way when I started brewing smaller batches, where small water inaccuracies lead to big gravity misses. Through my efforts to be more accurate, I learned how much measuring cups and pitchers graduations vary. Unless you use scientific vessels, measuring vessels are just “approximately” accurate. To avoid this, consistently use the same measuring vessels when measuring your brewing volumes.

“Put me in coach…”

Over the years I’ve found some tactics, methods and techniques to save my brew day.  I didn’t invent these, smarter people than me discovered them. I’m simply going to share what I’ve found to save you some time researching them. As friends and family can attest, I’m a bit of a perfectionist. So when I take a pre-boil gravity reading and confirm my miss, I’m usually angry and frustrated. Charlie Papazian’s famous quote; “relax and have a homebrew” definitely does not apply to how I brew.  A large part of my “joy of homebrewing” comes from “nailing” my numbers. As well as making a quality and good tasting beer.

My “go to” pitch…

As I said, I’m usually angry and frustrated when I miss my pre-boil gravity. Because of this, my first choice for fixing my problem is to adjust my boil time. If I overshoot my gravity, I shave time off my boil. If I’ve undershot my gravity, I’ll boil longer to concentrate the wort. Here are pro’s and cons of both approaches:

This is my “go to” method for fixing my wort since I find it easy to monitor my gravity as I boil using a refractometer. This method is much more of a challenge if you are using a hydrometer since you need a larger sample of wort and it requires more of an effort to adjust wort sample temperatures to get accurate readings. When choosing either of these methods, it’s critically important to adjust your hop schedule and additions to account for longer or shorter boil times. If you fail to do this, your beer will be either not hoppy enough or too hoppy for the style you are brewing. Hop adjustments can he made using your brewing software or using one of the many free brewing calculators available online.

My “change-up”…

If you’ve undershot your pre-boil gravity, likely the most popular method for saving your brew day is adding DME (Dry Malt Extract) or LME (Liquid Malt Extract) to your boil. Carefully adding these to your wort will boost its gravity to desired levels. Use your brewing software or one of the many free online brewing calculators to determine how much to add to your boil. Light DME adds approximately 45 points/gallon when added, while LME adds about 37 points/gallon.

If you over-shot your pre-boil gravity, you can add water to dilute your wort to your target gravity. Again, you can use your brewing software or free online brewing calculators to determine how much water to add. Diluting the wort can also be done at the end of the boil after chilling the wort. Ideally this should be done using sterile water to avoid any unintentional contaminants being introduced to your sterilized wort. 

A “curveball”…

Though I’ve never done it, gravity adjustments can be made in the fermenter. Sugar can be added to the post-boiled wort to increase gravity. On average, adding a pound of sugar will get you a 10-point gravity increase (1% in alcohol) in a 5-gallon batch. However, adding sugar post-boil could have a detrimental effect on the body of the beer, thinning it out. Adding it will add alcohol, but not flavor or body. In fact, it could unbalance your beer in terms of flavor, mouthfeel and hop profile.

A “Knuckleball”…

There are a couple of additional tactics to consider when wanting to close your gravity miss. Yeast choice can have a big effect on your final OG. When undershooting your OG, choosing a higher attenuating yeast could make up some lost ground and close the gap to your target ABV. Likewise, choosing a lower attenuating yeast could lessen attenuation and help you reach your desired target ABV when you overshot your OG. Understand changing yeasts could have a dramatic effect on your final beer, so choose wisely. Closely study the yeast profile and characteristics to be sure you understand if its appropriate for the beer style you are making. Fully understand what else your yeast choice will change about your overall beer before making the final decision.

As I mentioned earlier, misses in mash temperature can have a dramatic effect on your beers’ final gravity (see above). If you understand the effects and magnitude of your mash temperature miss, you can play with the impact to make up lost ground during attenuation. For example, if your mash temperature was lower than desired, you can expect your wort to attenuate more than you planned. This may close a gravity gap, helping you reach your desired ABV. Knowing this, you may choose to stay with the starting pitcher and ignore the bullpen all together.

Who’s in your bullpen?

These are my relief pitches, what are some of yours? Please share below, so we can all learn from each other. Good brewing!