Trying to achieve repeatability - looking for opinions

[TheHappyHopper]

So I have been brewing for a few years and up to now my philosophy has pretty much been "who cares if my efficiency/OG/etc. is off a bit from day to day, in the end I still get delicious beer!"

I know that I can get a program like Beersmith to do all of the calculations for me, but I am an engineer by day and I want to understand where all of the calculations come from. I have built my own spreadsheet that I use for keeping track of recipes and recording all of my brew day stats. I have gotten to the point where I not only want to make delicious beer, but I also want my recipes to be as identical as possible from batch to batch.

The issue that I run into is that, for example, some days I may get an efficiency of 70%, others I may get 74%...some days I boil off x amount of water, others I boil off slightly more/less amounts of water based on the outside temp/humidity and the strength of the boil...

So now I am looking for the opinions of those who may be a bit OCD about this too...

Is there a way to perfectly hit your OG, IBUs, Volume, etc. every time? Do you adjust your OG post-boil with water to make sure you hit your target OG? Would it be better to adjust pre-boil? If I end up with lower efficiency than expected, should I calculate how much longer to boil?! But what if my boil-of rate varies due to temperature/humidity conditions?!?!

Of course I am probably just waaaaaay overthinking all this...
:cross:

I guess my thought is, if I am going to tweak a recipe from batch to batch to try to perfect it, I want to know that I am actually seeing the effects of the things that I tweaked, and not that things are slightly different due to some of those factors mentioned above.

 

[m00ps]

I dont even measure the amount of water I add, but I would venture to say no, there isnt a way. Even commercial breweries have variations batch to batch after dialing in their process hundreds of times.

With the variation in yeast health, hop storage/age/harvest year, grain freshness, etc its impossible to hit the same number every time. Just let things ride and enjoy the beer IMO

 

[trentm]

So I have been brewing for a few years and up to now my philosophy has pretty much been "who cares if my efficiency/OG/etc. is off a bit from day to day, in the end I still get delicious beer!"

I know that I can get a program like Beersmith to do all of the calculations for me, but I am an engineer by day and I want to understand where all of the calculations come from. I have built my own spreadsheet that I use for keeping track of recipes and recording all of my brew day stats. I have gotten to the point where I not only want to make delicious beer, but I also want my recipes to be as identical as possible from batch to batch.

The issue that I run into is that, for example, some days I may get an efficiency of 70%, others I may get 74%...some days I boil off x amount of water, others I boil off slightly more/less amounts of water based on the outside temp/humidity and the strength of the boil...

So now I am looking for the opinions of those who may be a bit OCD about this too...

Is there a way to perfectly hit your OG, IBUs, Volume, etc. every time? Do you adjust your OG post-boil with water to make sure you hit your target OG? Would it be better to adjust pre-boil? If I end up with lower efficiency than expected, should I calculate how much longer to boil?! But what if my boil-of rate varies due to temperature/humidity conditions?!?!

Of course I am probably just waaaaaay overthinking all this...
:cross:

I guess my thought is, if I am going to tweak a recipe from batch to batch to try to perfect it, I want to know that I am actually seeing the effects of the things that I tweaked, and not that things are slightly different due to some of those factors mentioned above.

I'm with you on this, doing your best to control all the variables is the only way to understand the effect of the variable of interest. For me, the biggest challenge is that the quality of ingredients available to homebrewers cannot, for the most part, be verified. Quality of malt can vary from different suppliers, seasons, even lots. Hops are also variable and as mentioned above yeast health and viability can also have a tremendous impact on the final beer. For malt and hops, perhaps it's best to source these ingredients from larger suppliers as they probably have more invested in quality control or suppliers known to have consistent quality. Yeast health is the biggest variable in my opinion and that's why I maintain a yeast library and grow up fresh from storage for each batch. Of course fermentation temperatures should be controlled from batch to batch or varied for experimental effects. Water can also be controlled via knowledge on the forum. Concerning boil off: I attempt to visualize a consistent boil rate and maintain that rate from batch to batch. Although, environmental condition may make that more of a challenge, if a constant boil is maintained, perhaps the difference will be small. For adjustments, I believe it's better to top up than to boil longer due to the effects on hops extraction.

 

[TheHappyHopper]

Thank you for the feedback!

With the variation in yeast health, hop storage/age/harvest year, grain freshness, etc its impossible to hit the same number every time. Just let things ride and enjoy the beer IMO

That is a good point. I admittedly hadn't given much thought to the idea that there could be slight differences in the malts from year to year.

I believe it's better to top up than to boil longer due to the effects on hops extraction

My thought was that I could do something along the lines of...
- I found that my pre-boil gravity is lower than it needs to be!
- Since I have a pretty good idea of what my boil off rate is, if I know my pre-boil volume, I can calculate that I need to boil 68 minutes rather than the typical 60 to hit the post boil gravity that I want
- Throw in the hops at the same time that I would have (i.e. throw in the 60 minute bittering hops after it has boiled for 8 minutes - that way my extraction rates are not too far off from what was expected)

I suppose what it boils down to (pun intended) is: there are going to be some variables that I can't completely control at the homebrew scale, but as long as my processes are consistent, the more likely I am that I can produce a beer that is as close as possible from batch to batch. And for the most part, those little differences that I can't control may or may not make a perceptible difference from batch to batch.

So then that brings up this question for debate: when trying to reproduce the same beer at the homebrew scale - what % error is acceptable (to the point where it won't make a perceptible taste difference)? For example, if I am within +/- 2 gravity points of where I intended to be then I earn the title of Brewing Badass...

 

[p_p]

Thank you for the feedback!



That is a good point. I admittedly hadn't given much thought to the idea that there could be slight differences in the malts from year to year.




My thought was that I could do something along the lines of...
- I found that my pre-boil gravity is lower than it needs to be!
- Since I have a pretty good idea of what my boil off rate is, if I know my pre-boil volume, I can calculate that I need to boil 68 minutes rather than the typical 60 to hit the post boil gravity that I want
- Throw in the hops at the same time that I would have (i.e. throw in the 60 minute bittering hops after it has boiled for 8 minutes - that way my extraction rates are not too far off from what was expected)

I suppose what it boils down to (pun intended) is: there are going to be some variables that I can't completely control at the homebrew scale, but as long as my processes are consistent, the more likely I am that I can produce a beer that is as close as possible from batch to batch. And for the most part, those little differences that I can't control may or may not make a perceptible difference from batch to batch.

So then that brings up this question for debate: when trying to reproduce the same beer at the homebrew scale - what % error is acceptable (to the point where it won't make a perceptible taste difference)? For example, if I am within +/- 2 gravity points of where I intended to be then I earn the title of Brewing Badass...

Why not to always overshoot for OG purposely and top up with cold water after boil to hit the exact OG you want for your beer?

Your final volume may vary slightly, but that's not as critical as variations on your Og. Plus the top up water could be near freezing to help bring the temp to pitching target faster.

 

[dmtaylor]

I too am an engineer and tend to think a lot about the brewing process and how to make it easier and more predictable... more efficient!

One thing I learned early on was that original gravity points plus efficiency is nearly a constant for any recipe, as long as the rest of the process remains basically the same (mash time, boil time, sparge volumes, etc.). In other words, if I'm getting 75% efficiency on average with a 1.060 recipe, then my own personal constant (nearly constant anyway) is 75 + 60 = 135. I can then brew any other recipe with any other original gravity and determine the effect on efficiency by simple subtraction. So, for a 1.070 beer, I know my efficiency will dip by about 10%, 135 - 70 = 65% efficiency. And so on.

Now here's where it gets a little complicated. In reality, the near-constant is not constant. Figure at the low end, you'll hit a brick wall where at say 1.045, you'll only be able hit 90 or 95% efficiency maximum. So then your constant maxes out at about 45 + 95 = 140 when original gravity is quite low, and for most people will actually be much less than this, with a "constant" of just 125 or 130 since they can't seem to be able to hit 95% efficiency for various reasons. And then from about 1.075 and above, your constant actually stays constant, at around 140 to 150. If you really get into this, you'll do as I did and make a pretty graph with asymptotes and the whole thing that visually shows all of this, and can thus formulate exactly what your expected efficiency will be for any given original gravity of your recipe you want to brew.

With this technique, my OGs have become extremely predictable for any recipe. I can nail the OG on just about any recipe within 2 or 3 points without trying.

Bottom line is, don't expect your efficiency to remain constant for different recipes and different gravities. Everyone will tell you it should remain constant. Everyone is wrong.

 

[doug293cz]

Mash (to kettle) efficiency is fairly deterministic and straight forward to control if batch sparging. I'm not sure about fly sparging, as it is a much more difficult process to model (it's a dynamic process, and thus requires differential equations to model.)

Mash efficiency is the product of two factors: conversion efficiency and lauter efficiency.

Mash Efficiency = Conversion Efficiency * Lauter Efficiency​

Conversion efficiency can be monitored during the mash with SG samples. For most gain bills (that are mostly base grain), the sugar potential is about 80% by weight on a dry basis, and moisture content of the grain is typically 4%. So, it turns out the wort SG in the mash @ 100% conversion is a function of only the water to grain ratio. You can determine how close you are to 100% conversion by comparing your mash SG to the table found here: http://braukaiser.com/wiki/index.php?title=Understanding_Efficiency#Measuring_conversion_efficiency You can then extend the mash time as necessary to get your target conversion efficiency. For this monitoring to work well, you need to measure grain weight and strike water volume accurately. A consistent crush and good mash pH are required for consistent mash times, which still may vary with mash temperature.

For batch sparging it is straight forward to model the lauter efficiency. For the model to be valid, the sugar concentration throughout the mash needs to be uniform prior to each run-off (initial or sparge.) Uniform sugar concentration can be attained by aggressive mixing prior to any run-off (vorlauf after mixing.) The lauter efficiency then depends only on the following variables:

• Grain bill extract potential
• Grain moisture content
• Grain bill weight
• Strike water volume
• Sparge water volume(s)
• Apparent grain absorption
• MLT undrainable volume

For example if we assume a typical apparent grain absorption of 0.12 gal/lb, with a single batch sparge, and strike and sparge volumes adjusted for equal run-off volumes, we get the following set of curves for efficiency vs. grain bill weight for various MLT undrainable volumes (grain assumptions are the same as above in the conversion discussion):



The uncontrollable (by the brewer) variable for the mash output is the potential of the grains due to lot variability. Some maltsters do publish malt analyses for each lot, and if you can get this information, you can adjust your brew session predictions for this.

Boil-off can be monitored at various points in the boil, and boil-off at any elapsed time in the boil can be compared the predicted boil-off at that point. Heat input can then be adjusted to increase or decrease boil-off going forward, as needed.

None of the above helps with variability due to hops or yeast.

Brew on