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General Category => All Grain Brewing => Topic started by: chadchaney97 on March 16, 2013, 06:49:11 PM

Title: Preboil Gravity off
Post by: chadchaney97 on March 16, 2013, 06:49:11 PM
My preboil OG is consistently off by about 10, example 1.040 is 1.030, etc.  Always seems to roll this way, nay ideas?
Title: Preboil Gravity off
Post by: duboman on March 16, 2013, 07:19:49 PM
Things to evaluate:
Crush quality
PH
Water to grist ratio
Temp
Sparge method
Sparge temp
Equipment-bazooka screen, manifold, false bottom?

Maybe tell us your process and can chime in accordingly
Title: Re: Preboil Gravity off
Post by: tygo on March 16, 2013, 08:00:38 PM
Is your actual efficiency relatively consistent?
Title: Re: Preboil Gravity off
Post by: hellbound on March 16, 2013, 08:45:42 PM
Things to evaluate:
Crush quality
PH
Water to grist ratio
Temp
Sparge method
Sparge temp
Equipment-bazooka screen, manifold, false bottom?

Maybe tell us your process and can chime in accordingly

+1
It sounds like just poor efficiency, could be attributed to alot of things.
Title: Preboil Gravity off
Post by: duboman on March 16, 2013, 09:25:30 PM
Is your actual efficiency relatively consistent?
+1
If this is a consistent issue you can change your efficiency % and just add some grain to your recipes as well!
Title: Re: Preboil Gravity off
Post by: Wort-H.O.G. on March 16, 2013, 09:46:35 PM
My preboil OG is consistently off by about 10, example 1.040 is 1.030, etc.  Always seems to roll this way, nay ideas?

Do you crush or received crushed grains? Kits can come a little coarse and hurt efficiency.

What is your mash process- qt/lb, batch or fly sparge, single infusion...etc.
Title: Re: Preboil Gravity off
Post by: stephanehml on April 12, 2013, 12:03:46 PM
My preboil OG is consistently off by about 10, example 1.040 is 1.030, etc.  Always seems to roll this way, nay ideas?

Take your gravity at 20°C, not at 100°C.
Title: Re: Preboil Gravity off
Post by: wckedpete on April 13, 2013, 10:00:44 PM
If you were hitting the gravity before and now magically you are not, I would check the milling of your grain first. If you have never hit your gravity, it could be your system.
Title: Re: Preboil Gravity off
Post by: euge on April 14, 2013, 11:42:05 AM
My preboil OG is consistently off by about 10, example 1.040 is 1.030, etc.  Always seems to roll this way, nay ideas?

Take your gravity at 20°C, not at 100°C.

+1

Also, I've found a preboil gravity reading to be utterly useless and a complete waste of time.
Title: Re: Preboil Gravity off
Post by: jimrod on April 15, 2013, 06:44:45 AM
 Crush quality
PH
Water to grist ratio
Temp
Sparge method
Sparge temp
Equipment-bazooka screen, manifold, false bottom

I had the same problem and was very careful to correct all of the above. Then I got rid of the bazooka screen and added a false bottom and it changed everything. Gained 10 pts.
Title: Re: Preboil Gravity off
Post by: AmandaK on April 15, 2013, 02:41:34 PM
My preboil OG is consistently off by about 10, example 1.040 is 1.030, etc.  Always seems to roll this way, nay ideas?

Take your gravity at 20°C, not at 100°C.

+1

Also, I've found a preboil gravity reading to be utterly useless and a complete waste of time.

Really? Why?

Also, have you checked your hydrometer's calibration in water?
Title: Re: Preboil Gravity off
Post by: gsandel on April 15, 2013, 03:29:23 PM
I haven't figured out what in beersmith tweaks that pre-boil gravity number.  Mine is consistantly off by about 10 points (I always have a higher number than BS says I should), but end up within 1-3+/- of my original gravity target and I don't run off 15.57 gallons in my 15.5 gallon keggle as it tells me to (so it is not at all concerning).

I figure for me it is a combination of the equipment settings in BeerSmith, (it doesn't have a keggle setting), an estimation of what my deadspace in the mash tun is (I never checked), and that for whatever reason, my vigorous boil does not evaporate at the same rate that BS thinks it should....(I am at altitude, but I would figure my boil off rate would be higher, not lower, but boil temp is lower here, too).

At any rate, I feel like hitting your expected pre-boil gravity is an indication that you have done everything properly and all systems are go!
Title: Re: Preboil Gravity off
Post by: euge on April 15, 2013, 07:36:50 PM
The problem with a preboil gravity reading is that if your water volume is off then most likely your numbers will be skewed. But, this doesn't necessarily mean that the final numbers will be off.

I've found that the most beneficial gravity reading is at flameout and when it is certain that the desired and expected volume is correct. 
Title: Re: Preboil Gravity off
Post by: gman23 on April 15, 2013, 07:44:52 PM
I take a preboil gravity reading for every batch since I know exactly what my preboil volume is. When I take my post boil gravity I can calculate the exact post boil volume thus getting a more accurate efficiency. My buckets are only calibrated in 1/2 gallon increments so I like to know my post boil volume more accurately...
Title: Re: Preboil Gravity off
Post by: klickitat jim on April 15, 2013, 08:02:48 PM
I use refractometer for first run, start boil, end boil, then a hydro reading of what ends up in the fermentor.

"Freedom is temporary unless you are also Brave!" - Patriot

Title: Re: Preboil Gravity off
Post by: Mark G on April 15, 2013, 09:25:23 PM
To be perfectly honest, if my preboil gravity and volume are on target, I don't even bother checking again postboil. I know how much water boiled off, and the sugars aren't going anywhere, so why bother.
Title: Re: Preboil Gravity off
Post by: duboman on April 15, 2013, 09:31:45 PM
I always take a pre-boil reading as it only takes a minute but I really don't lose sleep on it.If it's a little low I'll just adjust the boil a bit. Since I started adjusting my water and milling my own grain I have found that I 'm always 80% efficient in the mash/lauter and have been using the same equipment for over two years so I'm pretty dialed in. I guess I just keep doing it out of habit:D
Title: Re: Preboil Gravity off
Post by: malzig on April 16, 2013, 12:55:35 AM
To be perfectly honest, if my preboil gravity and volume are on target, I don't even bother checking again postboil.
Same here.  I used to check, but my post-boil gravity was always what the pre-boil gravity and volume predicted it to be.  I think the pre-boil gravity is the second most important, since that is your best chance to correct the hopping rate if the gravity is off.  First is the mash gravity, since that tells you that your mash has fully converted and that your gravity expectation will be met.

Once you know your system, the kettle volume should be a given.  You know how much water you put in, you know your dead space, and you know how much grain you used, therefore your absorption.  It shouldn't be much of a mystery.  I measure the kettle volume just to confirm that it is the volume I expected.
Title: Re: Preboil Gravity off
Post by: tschmidlin on April 16, 2013, 08:49:53 AM
Also, I've found a preboil gravity reading to be utterly useless and a complete waste of time.
I agree if by "preboil" you mean before the boil, which it pretty much translates as.  I found I was not getting good mixing and any "preboil" gravity reading was off.

Now I take my "preboil" reading at the hot break, which is preboil as far as the hops are concerned but means it has been mixing for a while and gives me much nicer results.  I start timing my boil from there.
Title: Re: Preboil Gravity off
Post by: malzig on April 16, 2013, 09:41:39 AM
Now I take my "preboil" reading at the hot break, which is preboil as far as the hops are concerned but means it has been mixing for a while and gives me much nicer results.
Yes, it is a lot easier to get a fully mixed sample at boiling.  It's also easier to get an accurate kettle volume at this point, since you know the volume expansion is 4% at 212F.
Title: Re: Re: Preboil Gravity off
Post by: Mark G on April 16, 2013, 12:13:23 PM
Also, I've found a preboil gravity reading to be utterly useless and a complete waste of time.
I agree if by "preboil" you mean before the boil, which it pretty much translates as.  I found I was not getting good mixing and any "preboil" gravity reading was off.

Now I take my "preboil" reading at the hot break, which is preboil as far as the hops are concerned but means it has been mixing for a while and gives me much nicer results.  I start timing my boil from there.
Good point. I also wait until the beginning of the boil to take the "preboil" reading.
Title: Re: Preboil Gravity off
Post by: topher.bartos on April 30, 2013, 06:58:04 PM
Are you taking into account temperature?? Higher temperatures will lower the gravity by a few points.