Ultra low grain absoption with drain/fine crush?

[Andre3000]

I'm trying to sort out my method, now on biab brew #9.

I have a faily tight crush usually yeilding 85% on a consistent basis. After mash I hang the bag as it comes to a boil and usually let it sit 10 min into the boil ~ 30 min total usually.

My question is, I seem to be getting really low actual absorption from this. Eg I just finished bringing my current batch to a boil:

8 lb grains
9.5 lb bag weight after draining

So 1.5 lb / 8.34 lb/gal / 8 lb grain is only .022 gal/lb.

Most people seem to report upwards of .08-.10 gal/lb.

I'm not sure if this is correct, as weighing the grain doesn't account for sugars. Anyone else get absorption this low? It would partially explain why I've been overshooting my batch sizes consistently up to this point.

 

[pricelessbrewing]

That's not how it's measured. You measure how much total water you added to the mash, and you measure how much wort (volume) you got out of the mash. The difference is the apparent grain absorption rate.


If you want to go by the "wet grain mass" after the mash you'd have to measure the SG of the wort and do some more math. Since you didn't give any volume measurements, here's an example.

During the mash, the grain loses most of it's weight. Typically in the 70-80% range, given an average grain potential of 75% extract (ie 36 PPG), the succrose potential of 46 PPG, and ~95% conversion efficiency gives a wort extract weight of 8.92... lbs for a 12 lb grain bill which gives a grain weight loss of 75%.

Then the grains "true" absorption rate is usually 0.135-0.14 gal/lb for a 0.08 gal/lb APPARENT absorption rate, This is the ratio of the volume of WORT that the grain absorbs during the mash. It's a non linear relationship, so it doesn't scale with apparent, but just to give an idea.

 

[ScrewyBrewer]

After mash I hang the bag as it comes to a boil and usually let it sit 10 min into the boil ~ 30 min total usually.

I think the boil off from the kettle has the potential to keep the grains above it fairly wet. Have you thought about sparging the grains, then squeezing the grains to get the most wort from them?

 

[jalc6927]

I use .11 as my rate in my calculations to determine amount of water

 

[soccerdad]

I use .11 as my rate in my calculations to determine amount of water

Similar. I use .125

 

[Andre3000]

That's not how it's measured. You measure how much total water you added to the mash, and you measure how much wort (volume) you got out of the mash. The difference is the apparent grain absorption rate.


If you want to go by the "wet grain mass" after the mash you'd have to measure the SG of the wort and do some more math. Since you didn't give any volume measurements, here's an example.

During the mash, the grain loses most of it's weight. Typically in the 70-80% range, given an average grain potential of 75% extract (ie 36 PPG), the succrose potential of 46 PPG, and ~95% conversion efficiency gives a wort extract weight of 8.92... lbs for a 12 lb grain bill which gives a grain weight loss of 75%.

Then the grains "true" absorption rate is usually 0.135-0.14 gal/lb for a 0.08 gal/lb APPARENT absorption rate, This is the ratio of the volume of WORT that the grain absorbs during the mash. It's a non linear relationship, so it doesn't scale with apparent, but just to give an idea.

Thank you for that great explanation! I figured there was more to it than that. The trouble is I do not have an accurate way of measuring anything after I add all my strike water in the keggle/fermenters/etc. I suppose I need to get on it.

If the consensus is .1 gal/lb I wonder, then, how I'm overshooting my batches. I must be getting an extremely low boil-off rate around .5 gal/hour or less.

 

[Andre3000]

I think the boil off from the kettle has the potential to keep the grains above it fairly wet. Have you thought about sparging the grains, then squeezing the grains to get the most wort from them?

I thought about that too; but I even wondered if the steaming may actually be somewhat of a sparge in and of itself . I've fully subscribed to the hanging-and-done method as mucking around squeezing/sparging grains seems like way too much effort for a few efficiency points. I'm already well into the 80s consistently.

 

[wilserbrewer]

I've fully subscribed to the hanging-and-done method as mucking around squeezing/sparging grains seems like way too much effort for a few efficiency points. I'm already well into the 80s consistently.

Yes, yes and yes to hanging and draining and not mucking. No to the idea that steam from the kettle will increase grain absorption.

Measuring volumes is easy with a poor mans sight glass. Create a measuring dip stick or spoon with marks to show actual kettle volumes based on liquid depth.

 

[pricelessbrewing]

Or grab a stainless ruler that already has markings that are accurate!

 

[soccerdad]

Anybody got a lead on a stainless ruler with no cork back

 

[SleepyCreekBrews]

Might be better off buying one of the long stainless brewing spoons and using that (with your own engraved markings) .
Then you don't have to worry about the possibility of lead paint on a stainless yardstick

 

[raysmithtx]

I bought an aluminum yardstick from Lowes. Then printed out a chart cross referencing inches to gallons.

 

[chris000]

just a reminder regarding measuring volumes; obviously measure them at similar temperature (not cold water and just before the boil)

 

[pricelessbrewing]

https://www.staples.com/Gaebel-600-Series-Stainless-Steel-Ruler-24-In-600-24/product_2246413

If you're okay with aluminum then.

https://www.amazon.com/dp/B00ELMRFDI/?tag=skimlinks_replacement-20

 

[Andre3000]

Is there a possibility that hanging gives closer to .05 gal/lb? I recall I boiled it down from 1.043 to 1.053 in an hour, this calculates to 1 gal/hour roughly. The only way .1 gal/lb would make sense is if my boil-off was around .5 gal/hour.

For whatever reason these dipstick methods sound a bit janky. Maybe I'll have to cave for a sight glass... Or maybe I won't. Ha.

I do need to just measure it.

 

[pricelessbrewing]

My ruler measures down to 1/16th of an inch, which calculates out to like 6 ounces of fluid. That's way more precise than any sight glass or dip stick.

If you don't have volume measurements, then you can't determine your grain absorption.

 

[wilserbrewer]

OP is using a keggle which are not linear volume with respect to height. Simple dip stick imo better for a keggle. Fwiw you only need a few 1/2 gallon marks on the stick in the ranges of total water and post boil volume.

Interpolate b/w marks.

Only difference b/w a sight glass and a dip stick is that ones inside, and the other is outside the kettle, same concept.

 

[Andre3000]

Incase anyone is wondering, I finally put a sight glass on my setup. With my crush, I'm getting exactly .05 gal/lb absorption rate with bag drain until boil, no sparge, yeilding a very consistent 80% efficiency.

Boil-off is around 1 gal/hour.

 

[wilserbrewer]

I'm getting exactly .05 gal/lb absorption rate with bag drain until boil, no sparge, yeilding a very consistent 80% efficiency.

.

The squeezeaholics will never believe this. They look so forward to putting on their gloves and squeezing a freshly pulled wort laden bag, oh they feel they are being so productive.

I guess no one has explained gravity to them

 

[PADave]

Incase anyone is wondering, I finally put a sight glass on my setup. With my crush, I'm getting exactly .05 gal/lb absorption rate with bag drain until boil, no sparge, yeilding a very consistent 80% efficiency.

Boil-off is around 1 gal/hour.

That's the number I use. .2qt/lb = .05gal/lb

 

[jturman35]

I’m thinking of trying a batch without squeezing!

 

[wilserbrewer]

I’m thinking of trying a batch without squeezing!

Typically you don’t go cold turkey with the squeezing. Best approach is imo to let the bag drain for thirty minutes then give it a squeeze, this is the moment you realize there is not much left at all to squeeze so you gently fall out of love with the added effort of squeezing.

It’s a process of realization. You gotta learn your way out of squeezing, not just declare it, that will never work, the temptation is far too great.