Lower original gravity than expected

[shambala]

Hey guys, first time poster but long time reader and just started brewing a couple months ago. After fixing/correcting the mistakes on my first couple brews I thought I had the process down pat and my next one would be for the most part error free. This was not the case though and its why I am finally posting here today.

Extract Recipe (Hefeweizen 5 gallons):
6 lbs. Wheat LME
1 lb. light DME
8 oz. Carapils
1 oz. Tettnang
Safbrew WB-06 Dry Yeast

I was not sure how much to boil to account for evaporation, etc. so my starting volume was 8 gallons, steeped the grains for 30 minutes, boiled for 90 minutes, cooled using a CFC and aerated it all with an inline aeration stone and aquarium pump, stirred the wort a bit just in case, took 2 samples (1 from the bottom and 1 from the top) and my hydrometer read 1.04 both times, the wort was 78°F so the adjusted reading came out to be 1.042. The recipe says it should be 1.049-1.053. What did I or could I do to hit my target next time?

 

[doug293cz]

Hey guys, first time poster but long time reader and just started brewing a couple months ago. After fixing/correcting the mistakes on my first couple brews I thought I had the process down pat and my next one would be for the most part error free. This was not the case though and its why I am finally posting here today.

Extract Recipe (Hefeweizen 5 gallons):
6 lbs. Wheat LME
1 lb. light DME
8 oz. Carapils
1 oz. Tettnang
Safbrew WB-06 Dry Yeast

I was not sure how much to boil to account for evaporation, etc. so my starting volume was 8 gallons, steeped the grains for 30 minutes, boiled for 90 minutes, cooled using a CFC and aerated it all with an inline aeration stone and aquarium pump, stirred the wort a bit just in case, took 2 samples (1 from the bottom and 1 from the top) and my hydrometer read 1.04 both times, the wort was 78°F so the adjusted reading came out to be 1.042. The recipe says it should be 1.049-1.053. What did I or could I do to hit my target next time?

With extract, if your OG actually is low, it is because have more water diluting the sugar than you are supposed to have. With a given weight of extract, you have a fixed amount of sugar. That sugar doesn't go anywhere during boil (unless you boil over, spill, or similar.) What was your post-boil volume, and what was the recipe post-boil volume? Your answer lies there.

If you started with 8 gal, and boiled off 1 gal/hr, you'd have 6.5 gal post-boil. Since you had 42 gravity points/gal post-boil, your total points are 6.5 * 42 = 273. If your post-boil gravity had been 5.5 gal then you would have had 273 / 5.5 = 49.6 pts/gal => 1.049 - 1.050 OG.

Extract brewers sometimes have trouble getting accurate OG readings if they add top up water post boil. This is a mixing problem, as it takes a lot of vigorous mixing to homogenize high gravity wort and water. But since you took a top and bottom sample, and they were the same, this is not your problem.

Brew on

 

[shambala]

Thanks for the information and breakdown of the gravity points! I had a feeling it was the starting volume of water that caused it, at the time I figured I would start high so I could avoid topping off post boil. My post boil was pretty much right at 6.5 so you are spot on, Ill try 6.5-7 gallons next time and see what happens.

 

[ncbrewer]

You should still have a tasty brew. Enjoy.