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Obtaining volume by height measurement

Alright guys / gals, this request I understand will seem pretty vague. My holding container in question is identical to the 1 gallon jug sold by NB.

http://www.northernbrewer.com/shop/1-gallon-jug.html

Any advice on formulas I can use to obtain my actual internal volume by measuring the height of the internal contents.
If this bottom was not scalloped I could simply use the same formula I use for kettle volume.

I basically have a thick yeast slurry about .85 inches high on the bottom, and I’m curious of the rough ml measurement for pitching purposes.

:cheers:

edit: Being this was nearly all of a recent 3.5 gallon cake, I’m hoping it would be sufficient for a 5 gallon 1.086 batch. Either way I may through a 3 liter starter on it to be safe.

∏(Radius cm²)(Height cm)(Yeast Density Per ML)(Viability)= Viable Yeast Cells

Using the above formula with the dimensions you provided, and assuming 2 billion cells per ml at 75% viability.

I came up with ~590 Billion viable cells in your 1 gallon jug.

You may wish to recalculate this using more accurate numbers. I dont know the age or density of you yeast cake, so I just guessed at those.

Also, here is a very useful article in regards to this matter.

If you have another 1 gallon jug I would fill it up to the same level and then measure it in a measuring cup.

Thanks Greg!!

And TG, you posted as I was.

That is probably a more accurate way to calculate the volume. But the real variability is in the cake density and viability. Accurately calculating those values is very diffcult with out lab equipment. Really all we can do is make an educated guess based on experiments conducted by others like Jamil Zainasheff and Sean Terrill

Yep totally understood…seems alot of this brewing game is educated guesses…well without proper lab equipment.
I’m looking to need ~ 292 billion cells for the imp stout i’m brewing. This will be the first time I’m starting from so much yeast, I typically grow from 1/2 pint jars with much less.

Hopefully I estimate right and don’t over pitch this brew too much. Any opinions on safe(ish) over pitch levels?

[quote=“dsidab81”]Any opinions on safe(ish) over pitch levels?[/quote]Use 1/2 - 2/3 of the cake and you’ll be fine. If it’s less than a couple weeks old, don’t bother with a starter, but you could remove some of the yeast for later use, then add a half-gallon of the fresh wort to the gallon jug and let the yeast rev up for a couple hours before pitching.

BUt there is no real reason you couldn’t just pitch on the entire cake with a beer as large as an RIS … right???

Cause I have this one on the list of upcoming brews and my plan was to run a lighter beer, and not harvest the yeast as I like to when I run a low OG beer but instead just pitch onto the whole cake. Is that not ok?

Barry

[quote=“Vulkin’”]BUt there is no real reason you couldn’t just pitch on the entire cake with a beer as large as an RIS … right???

Cause I have this one on the list of upcoming brews and my plan was to run a lighter beer, and not harvest the yeast as I like to when I run a low OG beer but instead just pitch onto the whole cake. Is that not ok?

Barry[/quote]
Lets assume you will making 5 gallons of 1.100 RIS, that would require around 350 billion cells for proper pitching rates. Now we will assume your lighter beer will be 5 gallons of 1.040 ale, which would result in a final yeast cake of ~675 billion cells. Almost double what you will need for you RIS. You would probably get better results using ~2/3 of the yeast cake to ferment you RIS, instead of the whole cake.

Obviously all of the above is subject to what you actual volumes and gravities are. I guess the lesson would be to do a little math and try to get as close to the proper pitching rate as you can.

I guess an update is in order. I pitched roughly 2/3 of this 1056 cake into an imperial stout of 86 OG around 5.3 gallons.
This was after aeration with a wine whip leaving a very frothy wort, and the yeast topped of the carboy.

To top it off I pulled an idiot move and inserted my blow off too deeply…looking at it the next morning around 1/8 " above liquid level.
Needless to say my blowoff bucket the next morning was very yeasty and brown, and best I can figure fermentation shot off through the night and kicked the majority of my yeast out of the blow off. :twisted:
So now the wort is perfectly still with no krausen…plenty in the blowoff tube.
I assumed at this point that hopefully some yeast were left in suspension but not nearly enough for a proper fermentation, so i pitched a packet of us-05 to start things off again. Within 2 hours the carboy was chugging away again, so I am hoping all is good.

With all luck enough gravity points were knocked off by the initial pitch and mass exodus for 1 packet to not severely under pitch. Either way I plan on bulk aging for months, so by December I should know about the end product.

Looking back on it, before hastily pitching again I should have tested gravity to know exactly where I was and if 1 packet would suffice.
Either way I reached over the carboy for a six pack and had me a few homebrews to celebrate a glorious mis-adventure!!

:cheers:

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