Beer Forum

I am listening to this week's Session and there was talk about either not boiling long enough or nor boiling strong enough resulting in a lower than expected OG. With extract, I usually end up having a lower than expected OG. What can help this?

I have been doing partial boils: started w/ 3 gal and the last few doing 4 gal. My pot is big enough to go up to 5 gal or even 5.5 but my stove may not be strong enough to get that to a boil. With the partial boil, I have been adding water to make 5 gal in the carboy.

olafphysics wrote:I am listening to this week's Session and there was talk about either not boiling long enough or nor boiling strong enough resulting in a lower than expected OG. With extract, I usually end up having a lower than expected OG. What can help this?

I have been doing partial boils: started w/ 3 gal and the last few doing 4 gal. My pot is big enough to go up to 5 gal or even 5.5 but my stove may not be strong enough to get that to a boil. With the partial boil, I have been adding water to make 5 gal in the carboy.

if its consistently low OG, i would just add more base malt(in your form is DME or LME) to get to your target OG... take a sample once you get your wort up to a boil and check the gravity...if its low, then add more extract...

The boiling issues resulting in a low og is related to evaporation rate in an full boil system. In other words, if you have 7 gallons preboil at 1056 and are planning on boiling down to 6 gallons to leave you with a gravity of 1066, but have a weaker boil, you may only lose 0.5 gallons to evaporation, and have 6.5 gallons at ~ 1061. With extract in a partial boil, this generally isn't going to be an issue, as a certain amount of malt and a certain amount of water will give you a particular OG. If you are consistently low, either your expected OG is based on slightly different numbers than what you are getting ( 38 ppg instead of 36, etc), you are topping off to over 5 gallons, or your hydrometer is giving you a false reading. The first thing I'd do is check your hydrometer if you haven't done that already, tap water should give you a reading of 1.000. If that seems ok, then as matt said, either add more extract to get where you want to be, or add less water at the end. How far off are your numbers that you are getting?

This also maybe as simple as calibrating your hydrometer... Mine always shows 3 points high... You could be hitting your mark and not know it!


Josh

Yeah, I have not calibrated my hydrometer lately - I've been lazy. And I am aware that the discussion on the show was referring to a full boil & predominately full grain. It just brought the question back to the front of my head.

How low I am has depended on the beer. Even if my hydrometer is a little off low, when I take my fg, it is never as low as it should be with a low hydrometer.

So, I will check my hydrometer the next time I brew (this weekend is visiting breweries in WI instead of brewing) and I will add some extra DME that I keep around for starters if I am low. (I usually don't have extra from the recipe).

It could also be your recipes. It's really common for the OGs provided with extract recipes to be off, especially recipes that have been converted from all-grain. Most conversions substitute extract for base malt but keep the specialty grains and predicted OG the same. Steeped specialty grains yield less fermentables that contribute to OG than mashed specialty grains. Because of this difference, it's pretty common to be 2-4 pts low on extract versions of converted recipes, and it's quite possible to be 8-10 pts low.

Are you brewing from kits, or are you following recipes from someplace?? Have you tried calculating the OG to compare with what you brewed and the recipe?

The other potential variable is your weight of extract. Weigh it on a scale rather than trusting the number on the package. If you are already weighing check the accuracy of your scale as well as your hydrometer. Just a suggestion.

Bruce