Pre-Boil Gravity and other ?s

[snap1042]

I am a beginner all-grain brewer (2 5-gal all-grain batches up to now). The experiences created several questions. I followed the Palmer book as a guide.

1. What is the value in measuring a pre-boil gravity? If it is too high, isn't it easier to add water post-boil?
2. What do you do if your gravity is too low @ pre-boil? Just boil longer?
3. Is there a problem with pouring too much sparge water into the lauter tun? I had a couple quarts still in the tun when I had my pre-boil wort amount.
4. I assume the pre-boil gravity in recipes is corrected for temperature, correct?

Thanks for the help!
Mike

 

[Kaz]

1. The value in the pre-boil gravity is knowing if you're on target for the finished beer. If you know the pre-boil gravity, the pre-boil volume and how long you are going to boil, then you can make sure that you're on track for the target S.G. If you're volume is high, and gravity is low, you can boil longer. If you're gravity is low but you're volume is right on, then add DME to bring up the gravity. If the gravity is high, add water or make a stronger beer, but maybe add more hops to offset the increase in sugars/alcohol.

2. Answered above....

3. I BIAB so can't answer much to the sparge thing.

4. You want to measure your pre-boil using a hydrometer and then correct it for temperature (hard part is temperature in the sample is dropping pretty fast.) The other and better option is a refractometer which usually corrects for temperature and uses only a drop of wort. Your temperature corrected measurement should match the recipe pre-boil. HTH

 

[Kaz]

You should pick up a copy of "Designing Great Beers" it has some great chapters on gravity, hitting your target gravity and formulas to figure all of it out.

 

[Yooper]

I am a beginner all-grain brewer (2 5-gal all-grain batches up to now). The experiences created several questions. I followed the Palmer book as a guide.

1. What is the value in measuring a pre-boil gravity? If it is too high, isn't it easier to add water post-boil?
2. What do you do if your gravity is too low @ pre-boil? Just boil longer?
3. Is there a problem with pouring too much sparge water into the lauter tun? I had a couple quarts still in the tun when I had my pre-boil wort amount.
4. I assume the pre-boil gravity in recipes is corrected for temperature, correct?

Thanks for the help!
Mike

1. The preboil gravity "tells" you if you're on target. When I was dialing in my system, my readings were all over the place. Checking the preboil SG let me adjust the hopping (up or down, depending on the gravity) so if I missed by a lot I didn't have an 100 IBU 1.035 beer!

2. Yes, you can boil longer. But it's easiest to add a pound or two of DME to get you where you need to be. That also would keep your IBU/OG in the correct range.

3. If you're batch sparging, you want to only add the water to the tun that you're going to take out. Once you've added the water and stirred it, you've got the sugars in the liquid, so you don't want to leave it behind. You'd just use less water to reach your boil volume. I hope that makes sense! If you're fly sparging, some liquid will be left in the MLT.

4. Yes. And no.
The reason is simple, really. Any SG reading over about 90 degrees will NOT be accurate, even with a temperature correction chart. Cool the sample in a pitcher of cold water until it's under 100 degrees, then take a reading. And then use a temperature correction chart to get the corrected reading.