Trying to make sense of these gravity readings....

[Turfgrass]

Today I brewed a NEIPA using Beersmith 3 software. The estimated original gravity calculation by BS3 was 1.072 sg.

Using a refractometer my pre boil sg was 1.046 and post boil at 1.076. I checked for calibration accuracy and I was able to confirm 1.000 using distilled.

I also have a Tilt hydrometer in the fermenter, but I forgot to check for accuracy and it reported a starting gravity of 1.065

The brew was was on a HERMS setup. I am still trying to figure out how to best match up the rate of sparge water entering the MT and liquid to be boiled entering the BK. I try to go as slow as possible and stop once I hit my pre boil volume. Later on I did open OG the drain valve on the MT and collected another 3/4 of a gallon. Not sure how to have reduced that number lower without being able to see past the grain.

Curious as to how I did today and open to suggestions. Thx.

 

[mirthfuldragon]

Are you correcting the SG readings for temperature?
I like my Tilt, but it is not great for accurate readings without setting multiple calibration points (but it does a fine job of telling you fermentation activity and when fermentation stops).

 

[deadwolfbones]

With a refractometer you (usually) don't need to correct for temp.

 

[Rob2010SS]

Gotta ask, how much did you boil off during your boil? A 30 pt difference between pre boil and post boil? Brewers friend says that's about 3 gallons of boil off... 7.5 gallons pre boil to 4.5 gallons post boil.

With my system, I always try and keep about 1-2" of water on top of my grain bed during sparging. I also end up with a lot of excess water in the MT after collecting my pre-boil volume of wort. I really don't know any way around that other than trial and error. Maybe try killing the sparge water when you're 2 gallons away from pre-boil volume, and then on your next brew kill it when you're 3 gallons away from your pre boil volume and so on. You might be able to minimize the left over water this way.

Additionally, I don't think you're hurting anything by having the left over water. Every mash tun will have dead space in it where you wont' be able to collect that liquid no matter what. I think mine is .32 gallons. I don't think yours is .75 gallons but even if it's the same as mine, I don't think .75 gallons extra is bad. If you weren't hitting your expected OG and leaving a bunch of sugar behind, that's one thing, but it doesn't sound like that is the case here.

 

[Turfgrass]

I let the samples cool to room temp before testing, but the refrac has ATC.

 

[Turfgrass]

Gotta ask, how much did you boil off during your boil? A 30 pt difference between pre boil and post boil? Brewers friend says that's about 3 gallons of boil off... 7.5 gallons pre boil to 4.5 gallons post boil.

With my system, I always try and keep about 1-2" of water on top of my grain bed during sparging. I also end up with a lot of excess water in the MT after collecting my pre-boil volume of wort. I really don't know any way around that other than trial and error. Maybe try killing the sparge water when you're 2 gallons away from pre-boil volume, and then on your next brew kill it when you're 3 gallons away from your pre boil volume and so on. You might be able to minimize the left over water this way.

Additionally, I don't think you're hurting anything by having the left over water. Every mash tun will have dead space in it where you wont' be able to collect that liquid no matter what. I think mine is .32 gallons. I don't think yours is .75 gallons but even if it's the same as mine, I don't think .75 gallons extra is bad. If you weren't hitting your expected OG and leaving a bunch of sugar behind, that's one thing, but it doesn't sound like that is the case here.

There is a .25gal dead space in my MT, but that wasn’t included in what I drained. I actually did stop the sparge about 2 gallons from pre. Oil volume and will stop a bit sooner next time. I’m not sure what you mean by the 30 pint calculation. My system boils off at 1 gallon per hour and then there is some lose to hoses and dead spaces within the BK and chiller.

Sorry, but I don’t know how to screen shot on a iMac. According to BS3 my mash efficiency is low at 62.6%. I may tweak the grain crush a bit.

 

[Rob2010SS]

View attachment 617200
There is a .25gal dead space in my MT, but that wasn’t included in what I drained. I actually did stop the sparge about 2 gallons from pre. Oil volume and will stop a bit sooner next time. I’m not sure what you mean by the 30 pint calculation. My system boils off at 1 gallon per hour and then there is some lose to hoses and dead spaces within the BK and chiller.

Sorry, but I don’t know how to screen shot on a iMac. According to BS3 my mash efficiency is low at 62.6%. I may tweak the grain crush a bit.

I'll elaborate on what i meant. As you boil off volume during your boil, your gravity reading will increase because you're evaporating off water, right? So your pre boil gravity will be lower than post boil. I think we're on the same page there...

You stated that your pre boil was 1.046 and your post boil was 1.076. That's a 30 point difference (76 - 46 = 30). Plugging those numbers into brewers friend boil off calculator (see attached pic), it says you must have boiled off 3 gallons in order to hit that gravity reading when you started at 1.046.

It's not really important, it just seemed like a huge difference between pre boil gravity and post boil gravity. The difference in mine is usually 10-15 points so it caught my eye.

 

[Turfgrass]

I'll elaborate on what i meant. As you boil off volume during your boil, your gravity reading will increase because you're evaporating off water, right? So your pre boil gravity will be lower than post boil. I think we're on the same page there...

You stated that your pre boil was 1.046 and your post boil was 1.076. That's a 30 point difference (76 - 46 = 30). Plugging those numbers into brewers friend boil off calculator (see attached pic), it says you must have boiled off 3 gallons in order to hit that gravity reading when you started at 1.046.

It's not really important, it just seemed like a huge difference between pre boil gravity and post boil gravity. The difference in mine is usually 10-15 points so it caught my eye. View attachment 617202

I see what you are saying, but I was right on as far as the boil goes, so maybe I wrote it down wrong or something else happened. Definitely didn’t boil off 30 pints.

 

[Derp]

Sorry, but I don’t know how to screen shot on a iMac.

https://support.apple.com/en-us/HT201361

 

[Soulshine2]

View attachment 617200
There is a .25gal dead space in my MT, but that wasn’t included in what I drained. I actually did stop the sparge about 2 gallons from pre. Oil volume and will stop a bit sooner next time. I’m not sure what you mean by the 30 pint calculation. My system boils off at 1 gallon per hour and then there is some lose to hoses and dead spaces within the BK and chiller.

Sorry, but I don’t know how to screen shot on a iMac. According to BS3 my mash efficiency is low at 62.6%. I may tweak the grain crush a bit.

he meant 30 (gravity)POINTS not 30 pints.

 

[RPh_Guy]

Evaporation from the sample while it is cooling will give a falsely elevated reading.

I like my hydrometer. It's easy to use and always gives accurate readings.

 

[RM-MN]

Using a refractometer my pre boil sg was 1.046 and post boil at 1.076. I checked for calibration accuracy and I was able to confirm 1.000 using distilled.

My system boils off at 1 gallon per hour and then there is some lose to hoses and dead spaces within the BK and chiller.

With this bit of info, I'd conclude that you didn't stir the wort collected and took your gravity sample off the top of wort that was stratified. Next brew session, either stir before sampling or take the sample off the bottom (if you have a port there) and see if you get different numbers.

 

[Rob2010SS]

With this bit of info, I'd conclude that you didn't stir the wort collected and took your gravity sample off the top of wort that was stratified. Next brew session, either stir before sampling or take the sample off the bottom (if you have a port there) and see if you get different numbers.

That's an excellent point. I did not think about that. That would help make sense of this...

Pre boil gravity reading was 14 points low (red circle) and post boil gravity reading was 4 points high (blue circle).