A tale of two gravities (FG)

[NLSurfer]

Hi All,

I recently brewed an all grain batch using the parti-gyle method with one batch to become a lager (pressure lagered) and the other an IPA. The grain bill was as follows:

• 18 lbs Pilsner Malt (Avangard)
• 7 lbs Pale Malt (2 Row) UK
• 2 lbs Cara-Pils/Dextrine

I mashed at 150F. I have a setup with a RIMS tube, so before mashing out I heat and recirculate at around 170F before drawing from a hot liquor tank to fly sparge at 170F.

I mashed out to two boil kettles and equalized the volume to about 6.5 gallons each pre-boil. The pilsner OG ended up being 1.048 while the IPA was 1.078 as measured by hydrometer. I then used a RAPT Pill to monitor fermentation. I oxygenated using pure O2 and an air stone at 1L for about 2 min and added yeast nutrients to both batches. For the IPA I used Lutra Kveik at 95F and for the pressure lager I used SafLager W‑34/70 at around 68F under 1atm.

So, skip ahead about three weeks and the lager dropped to 1.012 FG (74% Att.) while the Lutra IPA is as 1.028 (63% Att) and hasn't budged in about a week and a half. I had stirred up the fermenter several times with no luck. I drew a sample from the fermenter of the Lutra IPA to verify gravity using a hydrometer and sure enough it matches the RAPT Pill (1.028). I tasted a sample and don't notice anything off.

So, I decided to keg the pressure lager and then rack the IPA onto the yeast cake of the lager 3 days ago. I have been tracking the gravity using the RAPT but it hasn't budged and there are no signs of fermentation in the fermenter.

Normally I might conclude that I mashed at too high of a temperature, or used too many unfermentables, but in this case the other half of the parti-gyle fermented down to 1.012 with issue.

Am I missing something here, has anyone else experienced this?

 

[hotbeer]

I mashed out to two boil kettles and equalized the volume to about 6.5 gallons each pre-boil. The pilsner OG ended up being 1.048 while the IPA was 1.078 as measured by hydrometer.

I don't have an answer for your question, but I am curious about the disparity in your OG's. When you say equalized the volume, did you just add more water to one of the boil kettles that had less wort in it? Or were they equal with wort and topped off with the same amount of water and just boiled off unequally?

Or were these two separate mashes and I'm misunderstanding that.

 

[NLSurfer]

I mash out initially to one kettle, producing a very high gravity wort and then divert the mash out to a second kettle (halfwayish during the mashout) for a low gravity batch. I then transfer some wort back and forth using a gallon measuring pot until both are around around the desired gravity.

 

[doug293cz]

You are using the term "mash out" incorrectly. What you are referring to is correctly termed "lautering," which means separating the wort from the grain. It's also called "running off."

A "mash out" is when you raise the temperature to ~170°F at the end of the mash, and hold for a few minutes, in order to denature all of the enzymes to keep the sugar profile (molecular weight distribution) from changing during lautering, especially when doing a fly sparge (which can take a while.)

Using agreed to definitions is key to understandable communications.

Brew on

 

[NLSurfer]

You are using the term "mash out" incorrectly. What you are referring to is correctly termed "lautering," which means separating the wort from the grain. It's also called "running off."

A "mash out" is when you raise the temperature to ~170°F at the end of the mash, and hold for a few minutes, in order to denature all of the enzymes to keep the sugar profile (molecular weight distribution) from changing during lautering, especially when doing a fly sparge (which can take a while.)

Using agreed to definitions is key to understandable communications.

Brew on

You are correct sir. I mash out by raising my mash temp to 170 using my rims tube before lautering to my kettles. I don't talk to enough brewers to fine tune my vocabulary!

 

[hottpeper13]

When I use Lutra in a low gravity beer I use 1/2 tps fermaid K in 5 gal. You used a second runnings wort that might be way low in nutes. Might need a full tps in that.

 

[NLSurfer]

When I use Lutra in a low gravity beer I use 1/2 tps fermaid K in 5 gal. You used a second runnings wort that might be way low in nutes. Might need a full tps in that.

The Lutra was used in the high OG mix, and the W-34/70 in the low gravity. I did add nutrient to both but it was DAP. I wonder if I should have added a more "diverse" nutrient instead of DAP. I thought transferring the Lutra IPA on top of the 34/70 yeast cake would do the trick, but still nothing.

On that note, does anyone ever add nutrient this late in the fermentation? I'm guessing it would be a bad idea...

 

[hottpeper13]

I wouldn't add more nutes for fear of the umami coming thru. I've gotten no less then 80% ADF on my Lutra's ,but I start them at 68-76 for 1-3 days them bump to 85. The Voss does well finishing at 90. I do step ferments with all my yeasts.