AG Issue looking for value added

[Summers]

I brewed a kolsch this weekend, and I had a problem which I need some help explaining what happened. I was brewing a 6 gallon batch, the target pre boil volume was 7.5 gal and the pre boil SG was 1.040, well After 5 gallons of collected wort, fly sparging at a rate of 1lt per every 80 sec I checked the of running's and the SG was 1.015 then after 5.5 gallons it was down to 1.010 so I stopped fly sparging. I ran the pump to recirculate the wort pulled a sample to checked my pre boil SG and it was 1.055.

All of SG reading are with a refractometer once the temp has reached 75 degrees.

Mill is set at .035" confirmed with a feeler gauge
Mash ratio was 1.25lt per lbs.
Mash pH was 5.6
End of sparge pH was 5.9 after 5.5 gallons of collected wort
First runnings SG was1.068
My mash temp was 148 for the full 60 min and I used a RIMS to control it and I raised the temp to 168 and held the mash for 10min.
Fly sparge was for 5.5 gallons at 168

So my question is what cased me to reach the end of sparge target of 1.010 at 5.5 gallons.

I was able to add water to reach the target pre boil volume of 7.5 gal which dropped the SG down to 1.039, so I stopped freaking out and boiled the wort hit the rest of the target values and just went on my way pitched the yeast and just let it ride. I am not to concerned about the beer. I am just trying to under what caused this problem so I can understand what I might have done wrong to increasing my understanding and learn from this.

Thanks
Summers

 

[MrHadack]

So my question is what cased me to reach the end of sparge target of 1.010 at 5.5 gallons.

Perhaps it was effective sparging? Congratulations.

Seriously, there's no problem here. Pre-boil volume is targeted at 7.5 gallons because you'll lose 1.5 in the boil and you're making a 6 gallon batch. It's not 7.5 gallons because that's how much liquid you'll necessarily need to collect through the sparging process to get down to 1.010 runnings. You ended up with 7.5 gallons and also hit your pre-boil gravity almost exactly. That's all that really matters.

So now you may ask, "Why check my final runnings then?" The answer has to do with efficiency. Let's pretend you hit 7.5 gallons of pre-boil volume in the kettle, and the final runnings were 1.020. This means there are still a decent amount of sugars left in the mash. Your pre-boil gravity would probably be higher than 1.040 as well. This means your mash efficiency is higher than what you planned for when designing the recipe. If this happens consistently it would be a sign that you can scale back the amount of grain needed to make the same beer in the future.

Now let's say the opposite happened. You get to 7.5 gallons pre-boil volume, but your pre-boil gravity is 1.030. That's 10 points too low. You check your final runnings and they're 1.008. Uh-oh! This indicates for some reason your efficiency was lower than what you planned. Something went wrong with the mash. If this happens over and over again with more batches, you'd need to use more grain to make the beer until you figure out why your efficiency is lower than expected. Make sense?

 

[Summers]

Thanks for the explanation.

 

[doug293cz]

I brewed a kolsch this weekend, and I had a problem which I need some help explaining what happened. I was brewing a 6 gallon batch, the target pre boil volume was 7.5 gal and the pre boil SG was 1.040, well After 5 gallons of collected wort, fly sparging at a rate of 1lt per every 80 sec I checked the of running's and the SG was 1.015 then after 5.5 gallons it was down to 1.010 so I stopped fly sparging. I ran the pump to recirculate the wort pulled a sample to checked my pre boil SG and it was 1.055.

All of SG reading are with a refractometer once the temp has reached 75 degrees.

Mill is set at .035" confirmed with a feeler gauge
Mash ratio was 1.25lt per lbs.
Mash pH was 5.6
End of sparge pH was 5.9 after 5.5 gallons of collected wort
First runnings SG was1.068
My mash temp was 148 for the full 60 min and I used a RIMS to control it and I raised the temp to 168 and held the mash for 10min.
Fly sparge was for 5.5 gallons at 168

So my question is what cased me to reach the end of sparge target of 1.010 at 5.5 gallons.

I was able to add water to reach the target pre boil volume of 7.5 gal which dropped the SG down to 1.039, so I stopped freaking out and boiled the wort hit the rest of the target values and just went on my way pitched the yeast and just let it ride. I am not to concerned about the beer. I am just trying to under what caused this problem so I can understand what I might have done wrong to increasing my understanding and learn from this.

Thanks
Summers

What were your actual grain bill weight, strike water volume, and assumed mash efficiency for the recipe? Your numbers don't seem self consistent to me, and I'd like to do some cross checking. In particular, at 1.25 L/gal (1.32 qt/gal), first runnings SG should be about 1.092 for 100% conversion efficiency. 1.068 works out to only 70% conversion efficiency, and mash efficiency is going to be even less, since mash eff equal conv eff times lauter eff, and lauter eff is always less than 100%.

Brew on

 

[Summers]

Grain bill was 10.5 lbs, beer smith gave me a mash volume of 13.5L and I added 2L of 168 degrees at mash out to help raise the temp, my assumed mash was set at 75% for this recipe.

 

[doug293cz]

Grain bill was 10.5 lbs, beer smith gave me a mash volume of 13.5L and I added 2L of 168 degrees at mash out to help raise the temp, my assumed mash was set at 75% for this recipe.

Ok, the extra water added for mash out makes a difference in max first runnings SG. At 100% conv eff, you would have been around 1.078, and your actual of 1.068 puts your conversion efficiency at 85%. With a pre-boil volume of 7.5 gal at 1.039, your lauter efficiency was about 94%, which is very good. and your mash efficiency was about 80%. 85% isn't particularly good conversion efficiency, but with your high lauter efficiency, you compensated.

Apparently, your fly sparge process is very effective at extracting maximum sugar from the grain bed with a minimal amount of sparge water. Thus your got your projected gravity points before you sparged enough to get your target pre-boil volume. Diluting the pre-boil wort put you right back on target. Well done.

Brew on