Specific gravity questions

[Smoketer10]

I was wondering if my starting gravity after batch sparging should be different from my after boil gravity (og vs bg) . I am new to this, just brewed my second batch, a red ale, and the two gravity readings were the same 1.047. I have heard that it should go up but can't find anything about it anywhere? Thanks for the help in advance...Chris

 

[lukeziegler]

well, I am new to this as well. But,from what i know, during your boil your losing quite a bit of liquid to evaporation, leaving behind the sugars. So you have a higher sugar content in a smaller amount of wort. Thus, higher gravity.

 

[slapnutz]

Did you adjust for temp? Did you stir your wort pre boil? You can get stratification of gravities if you don't. Have you calibrated your hydrometer?

 

[jro238]

As likeziegler said, because you decrease volume during the boil (evaporation) and lose no sugar, the gravity will increase. This increase will be directly proportional to the volume that you lose.

 

[vrodbrad]

I was with Chris on that day and it confused the heck out of me also. We did two batches, both a red ale. The one I did the SG of pre-boil and post boil changed, while the one that Chis did did not. He did stir and mix very well his pre-boil, that I don't believe was the the issue. We both used the same hydrometer so while I had two different readings and he did not is confusing the heck out of me. I know that with evaporation that the post boil should of gone up. Temp was adjusted for on both pre and post.

 

[Smoketer10]

Thank you all for replying. Slapnutz, I did all that you asked and yes the hydrometer is calibrated. And I understand what the other posts described about lose of water and higher sugar amounts thus higher readings. However, my starting and ending gravities were the same, they did not change and that is the confusing part. Could it be that I did not have my water temperature high enough when I steeped my grains? That would be the only thing that was out of the normal.?

 

[IL1kebeer]

Get a refractomenter if you want to make quick and precise gravity readings on the hot side. I personally only use my refractometer on the hot side and only use my hydrometer for the cold side. I used both on the hot side until everything was calibrated and consistent.

A hydrometer is too much trouble on the hot side. If you aren't letting your sample cool then you can't really temperature correct unless your sample is pretty close to the calibration point. If you are calibrated at 60F and are temperature correcting at 170F then you aren't getting accurate readings. To get accurate readings, you must cool your wort to close you your calibration temperature so that you can accurately use those temperature adjustment calculations. This is not exactly a fast way of doing things and will prohibit you from making adjustments on the fly. A refractometer solves these problems. Get one.

I'm not exactly sure what your process was but it seems to me that there was some user error with the hydrometer.

 

[Smoketer10]

The second reading from the hydrometer was after immersion chilling to 76 degrees. The process, steep the grains, batch sparge, boil, cool, pitch, ferment. A very simple recipe. It tasted great and that's what matters but I enjoy the science and wanted to find the reasoning behind the specific gravity not being different and understand how, if at all, it will effect the taste or ferment ability. Then next time, if it's as great after conditioning as it was at wort, I do it the same for that same great taste.