Author Topic: preboil vs postboil gravity  (Read 952 times)

Offline kylekohlmorgen

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Re: preboil vs postboil gravity
« Reply #15 on: January 22, 2014, 11:02:22 AM »
...Beer Smith uses Brewhouse in the eff field...

You can calculate both mash and brewhouse efficiency in your recipe.

I personally don't like "Brewhouse Efficiency" on the homebrew scale. Since it is affected by so many unrelated variables, it doesn't really tell you anything on its own. You end up looking at mash efficiency + other numbers to diagnose an unexpected result.

Either way, its more important to understand the numbers and what they mean to you. If you change your process or change your recipe, can you still get accurate numbers from the software?
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Re: preboil vs postboil gravity
« Reply #16 on: January 22, 2014, 11:13:09 AM »
I make sure that I take my samples after mixing the wort thoroughly. I do not however take my preboil reading after the hot break but right after collecting the second runnings.

I've experienced inaccurate readings due to stratification by doing that.
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Re: preboil vs postboil gravity
« Reply #17 on: January 22, 2014, 11:21:17 AM »
I make sure that I take my samples after mixing the wort thoroughly. I do not however take my preboil reading after the hot break but right after collecting the second runnings.

I've experienced inaccurate readings due to stratification by doing that.

So accuracy is still a worry if it is well mixed?

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Re: preboil vs postboil gravity
« Reply #18 on: January 22, 2014, 11:25:00 AM »
...Beer Smith uses Brewhouse in the eff field...

You can calculate both mash and brewhouse efficiency in your recipe.

I personally don't like "Brewhouse Efficiency" on the homebrew scale. Since it is affected by so many unrelated variables, it doesn't really tell you anything on its own. You end up looking at mash efficiency + other numbers to diagnose an unexpected result.

Either way, its more important to understand the numbers and what they mean to you. If you change your process or change your recipe, can you still get accurate numbers from the software?

Thanks. This makes the most sense to me. I am usually determining what my final volume should be by using preboil vol, preboil gravity and postboil gravity. This is obviously not accurate for me and I probably have incorrect approximations in beersmith for estimating volumes.

I think I need to work on calibrating a stick to put in the kettle for volumes...

Offline kylekohlmorgen

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Re: preboil vs postboil gravity
« Reply #19 on: January 22, 2014, 11:39:49 AM »
Thanks. This makes the most sense to me. I am usually determining what my final volume should be by using preboil vol, preboil gravity and postboil gravity. This is obviously not accurate for me and I probably have incorrect approximations in beersmith for estimating volumes.

I think I need to work on calibrating a stick to put in the kettle for volumes...

The boiloff / losses entered in the volumes tab are what got me! I had entered some numbers that weren't always constant and, depending on the beer/brewday, would throw off my expected SG/volume. It took a bit of playing with the numbers (and reading about efficiency calcs) to dial it in.

Now I account for mash efficiency and evaporation in the software, but trub losses manually. I increased my batch size to 6 gallons post-boil, not including trub/hop losses.

YMMV - I adopted this procedure because of my system's quirks: evaporation rate changes radically with the season and my losses to trub are different based on style.

For getting your kettle volumes: I use a tape measure to find the height of liquid in the kettle, then plug the height into a spreadsheet to get volume.
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Re: preboil vs postboil gravity
« Reply #20 on: January 22, 2014, 11:41:18 AM »
So accuracy is still a worry if it is well mixed?

I've never been able to get it mixed well enough.  If you're sure that you can, then it's fine.
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Re: preboil vs postboil gravity
« Reply #21 on: January 22, 2014, 12:54:58 PM »
Ok so I am pretty much a moron.

I was basically equating post boil volume and volume into the fermenter as the same. I have been calculating my post boil volume and entering that into batch size in Beersmith. Batch size is basically volume into the fermenter from what I understand.

I need to be measuring the 'post boil volume' right after the boil concludes hence the term 'post-boil'. That should resolve a lot of my confusion...

Sorry all and thanks for all of the help.


Offline kylekohlmorgen

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Re: preboil vs postboil gravity
« Reply #22 on: January 22, 2014, 02:55:06 PM »
Ok so I am pretty much a moron.

I was basically equating post boil volume and volume into the fermenter as the same. I have been calculating my post boil volume and entering that into batch size in Beersmith. Batch size is basically volume into the fermenter from what I understand.

I need to be measuring the 'post boil volume' right after the boil concludes hence the term 'post-boil'. That should resolve a lot of my confusion...

Sorry all and thanks for all of the help.

Yep - as long as you don't enter any post-boil losses in the "Volumes" tab, post-boil volume and batch size should be the same.
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Re: preboil vs postboil gravity
« Reply #23 on: January 22, 2014, 04:52:32 PM »
Went back to re-calculate my last 6 batches based on all mentioned variables. It looks like my mash efficiency is consistently about 5% higher than my brewhouse efficiency. Evaporation rates have ranged from 10.6% to 14.2% and batch size from 5.08 to 5.32 gallons. This is assumming constant losses for cooling and trub. I understand trub loss is variable but I don't use a lot of hops in most of my beers so I assume the difference would be minimal...

My calculated IBUs and SRMs were all higher than I originally thought and it makes sense after tasting them. Now that I better understand, I should be able to get my process further dialed in and get better results...
« Last Edit: January 22, 2014, 04:57:15 PM by goschman »

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Re: preboil vs postboil gravity
« Reply #24 on: January 22, 2014, 05:11:58 PM »
Went back to re-calculate my last 6 batches based on all mentioned variables. It looks like my mash efficiency is consistently about 5% higher than my brewhouse efficiency. Evaporation rates have ranged from 10.6% to 14.2% and batch size from 5.08 to 5.32 gallons. This is assumming constant losses for cooling and trub. I understand trub loss is variable but I don't use a lot of hops in most of my beers so I assume the difference would be minimal...

My calculated IBUs and SRMs were all higher than I originally thought and it makes sense after tasting them. Now that I better understand, I should be able to get my process further dialed in and get better results...

You're getting there,man. Getting your process (with all the many variables) dialed in is the toughest part of AG brewing IMO, and one of the most rewarding when you get there. It takes everybody some time. But you're on the way !
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Re: preboil vs postboil gravity
« Reply #25 on: January 22, 2014, 05:16:29 PM »
Went back to re-calculate my last 6 batches based on all mentioned variables. It looks like my mash efficiency is consistently about 5% higher than my brewhouse efficiency. Evaporation rates have ranged from 10.6% to 14.2% and batch size from 5.08 to 5.32 gallons. This is assumming constant losses for cooling and trub. I understand trub loss is variable but I don't use a lot of hops in most of my beers so I assume the difference would be minimal...

My calculated IBUs and SRMs were all higher than I originally thought and it makes sense after tasting them. Now that I better understand, I should be able to get my process further dialed in and get better results...

You're getting there,man. Getting your process (with all the many variables) dialed in is the toughest part of AG brewing IMO, and one of the most rewarding when you get there. It takes everybody some time. But you're on the way !

Thanks! Funny that I have been doing all grain for almost 3 years now... I thought my process and measurements were good but I realize that I was basically half-assing it. Hopefully I am on the way to making some solid, reproduceable beers!

I should probably work on my water next...
« Last Edit: January 22, 2014, 05:18:56 PM by goschman »

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Re: preboil vs postboil gravity
« Reply #26 on: January 22, 2014, 05:27:16 PM »
Went back to re-calculate my last 6 batches based on all mentioned variables. It looks like my mash efficiency is consistently about 5% higher than my brewhouse efficiency. Evaporation rates have ranged from 10.6% to 14.2% and batch size from 5.08 to 5.32 gallons. This is assumming constant losses for cooling and trub. I understand trub loss is variable but I don't use a lot of hops in most of my beers so I assume the difference would be minimal...

My calculated IBUs and SRMs were all higher than I originally thought and it makes sense after tasting them. Now that I better understand, I should be able to get my process further dialed in and get better results...

You're getting there,man. Getting your process (with all the many variables) dialed in is the toughest part of AG brewing IMO, and one of the most rewarding when you get there. It takes everybody some time. But you're on the way !

Thanks! Funny that I have been doing all grain for almost 3 years now... I thought my process and measurements were good but I realize that I was basically half-assing it. Hopefully I am on the way to making some solid, reproduceable beers!

I should probably work on my water next...

It's tough, and I made it that way for awhile back then too. It evidently wouldn't sink in on the first few batches that getting water volumes spot on was pretty important - as in, collecting exactly 7 gallons of wort to boil it down to exactly 5.5 like I usually do now for normal strength beers, and the relationship between doing that and hitting my target gravity. Little stuff like that !   ;)

<EDIT>   Water was another thing I resisted addressing for a while too !
« Last Edit: January 22, 2014, 05:49:42 PM by HoosierBrew »
Jon H.