What causes low OG?

[Mr_Turtlehead]

Brewed up my second batch today...a "Texas Bock" from Austin Homebrew. And followed everything to a "T" or so I thought. Made 2.5 gallons of wort, chilled to 80 degrees and transferred to primary with another 2.75 gallons of spring water (instructions said to bring to a total of 5.25 gallons) and mixed well. My only deviation from the recipe was to add Irish Moss with 15 minutes left and to siphon wort off of trub with 1/2 inch of liquid left in brew pot. My SG read 1.038 while the sheet said it would be 1.045. Would siphoning off the wort make for a lower OG (instructions read to pour contents of brewpot into primary)? What can I expect for a final product....lower alc content? more bitter? Thanks in advance.

 

[Genghis77]

Generally, a low OG is attributed to the addition of too much water.

 

[homebrewer_99]

...and/or not enough fermentable sugar...

 

[El Pistolero]

Brewed up my second batch today...a "Texas Bock" from Austin Homebrew. And followed everything to a "T" or so I thought. Made 2.5 gallons of wort, chilled to 80 degrees and transferred to primary with another 2.75 gallons of spring water (instructions said to bring to a total of 5.25 gallons) and mixed well. My only deviation from the recipe was to add Irish Moss with 15 minutes left and to siphon wort off of trub with 1/2 inch of liquid left in brew pot. My SG read 1.038 while the sheet said it would be 1.045. Would siphoning off the wort make for a lower OG (instructions read to pour contents of brewpot into primary)? What can I expect for a final product....lower alc content? more bitter? Thanks in advance.

How much liquid did you leave in the brewpot when you siphoned? What was the temp when you took your SG reading? If it was 78F say, then your corrected SG would be 1.041. There's not much diff from .041 to .045...may not even be able to taste the difference in bitterness.

 

[david_42]

Most likely the two quarts or so you left behind caused the difference. That would have been about 8% of your sugars, accounting for .003. Because you had to add an additional 2 quarts of water to bring it up to 5.25 gallons you lost another .002.

The ABV will be slightly lower, as will the IBU. Not enough to notice.

 

[Mr_Turtlehead]

Thanks everyone. It all makes sense. The temp was 76F when I took the reading.

Is there a multiplier/scale used to factor SG at different temperatures?

Also, I probably left behind a quart of liquid. Should I just dump it all in with future brews? I've read where you should try to leave as much trub out of the primary as possible.

 

[El Pistolero]

Is there a multiplier/scale used to factor SG at different temperatures?

It's around +.001 for every 6 degrees over 60F.

 

[david_42]

I've always used a filter of some kind when transfering from the kettle to the pail, I hate leaving wort behind. Technically, what is in the kettle is hops, hot break proteins and the crud Irish Moss binds to. Trub is what you leave behind going from the primary to the secondary. I transfer until I get some trub in the tube. The most of the rest goes in a pitcher to settle out, for Quality Assurance.

 

[rod]

i found what appears to be a good way to leave the trub behind.
after using my immersion chiller to coll the wort, ilet the wort sit 5-10 minutes in the bucket to let the cold break settle a bit. i then put a sterilized 5 gall nylon paint strainer over my colied copper chiller. i slowlly submerge the chiller in the wort.
the wort comes cleanly through the strainer and i syphon it into the fermenter with my racking cane. all the trub,hops is left behind.