[denny]

A difference in what? Runoff speed?  Mine is consistent whether the cooler is 1/4 full or completely full.

[euge]

Seems to me that when it gets thicker in the sense that lower grain to water ratio efficiency suffers. Which is what happens when brewers have maxed the tun capacity out.

In that case I'd rather do a third sparge. 

[richardt]

All these comments are very interesting and thought-provoking.  Depending on the sources, it seems that, for the homebrewer, the ideal grain bed depth is between 4-12 inches.  Perhaps counterintuitively, a deeper grain bed is more "efficient" (up to a point), but not necessarily "faster."  See JP's HTB Appendices E and F for more details, if interested.

A grain bed depth beyond 12 inches might have compaction issues in a 10 gallon round Igloo cooler (internal dimensions 12 inches diameter x 18 inches deep) given that the height would then exceed the width of the grain bed.  That situation (i.e., grain bed height exceeding its width) does not occur in a rectangular mash-lauter tun regardless of lauter design (e.g., false bottom, pipe manifold, or screen) or grist amount (e.g., high versus normal gravity recipe).

My personal observations with the high gravity brewdays seems to suggest slower lautering.  But, there are too many other potential variables (different recipes, different wort temps, mill gap settings, coarse vs fine grist, use of wheat, etc.) involved in order for me to really be able to say for sure.  So I certainly respect the views of those with far more experience.  Nonetheless, being a practical person, I think the hypothetical 3-D MLT design isn't.

[kerneldustjacket]

My personal observations with the high gravity brewdays seems to suggest slower lautering.  But, there are too many other potential variables (different recipes, different wort temps, mill gap settings, coarse vs fine grist, use of wheat, etc.) involved in order for me to really be able to say for sure.  So I certainly respect the views of those with far more experience.  Nonetheless, being a practical person, I think the hypothetical 3-D MLT design isn't.

{emphasis added by me. jw}

Someone else please chime in and agree or disagree...but I see two routes regarding high gravity brew days:
1. Conduct a parti-gyle, and get a high gravity first runnings beer and a mid to low gravity second-runnings beer.
2. Do one beer but fly sparge.

The issue, so far as I see it, lies in how much water is retained by the grains. This was suggested to me by Kai's chart that shows lower efficiency's as the target gravity goes up. (link below; about half way down)
http://braukaiser.com/wiki/index.php/Batch_Sparging_Analysis#True_v.s_apparent_grain_absorption

[denny]

Why couldn't you do one beer batch sparged?  I've done that many times.

[kerneldustjacket]

Why couldn't you do one beer batch sparged?  I've done that many times.

Yes, I'm sure you can Denny. I only recently converted from fly to batch sparging (partly you're fault, Denny!  ) so forgive my ignorance of what's possible.  Also I suppose that I'm thinking in terms of getting as much sugar as you can from a high gravity batch; either in one beer or as a parti-gyle, while also avoiding an overly long boil.

Do you get reasonable efficiency as your gravity increases?
Again, I'm flying off of Kai's chart here, and maybe looking at OGs that are above 1.095; but if you say you've done it then I have no hesitation about believing you.


Duh! I just realized I could make a direct link to Kai's chart:

http://braukaiser.com/wiki/index.php/File:Lauter_efficiency_and_wort_strength.gif

[denny]

My efficiency stays around 85% up to maybe 1.085 OG.  After that I either do a partigyle or sparge more (and of course boil longer) to keep efficiency up on bigger beers.  Pretty much like you'd do with fly sparging.

[kerneldustjacket]

My efficiency stays around 85% up to maybe 1.085 OG.  After that I either do a partigyle or sparge more (and of course boil longer) to keep efficiency up on bigger beers.  Pretty much like you'd do with fly sparging.

Yes...that's what I was proposing...tho I didn't say it as concisely as you did .
But I didn't define how high of a high gravity...so that's my fault.

Makes me wonder if we need to add a few terms to describe gravity:
(older folks will recognize the similarity to "HF" "VHF" & "UHF" from old radios and TVs)
HG: High Gravity...up to 1.085?
VHG: Very High Gravity...1.086 to 1.100?
UHG: Ultra High Gravity...1.101+


Also, I have to confess that the highest gravity I've ever brewed to was 1.084.

[bonjour]

UHG: Ultra High Gravity...1.101+

Ahhhh,
stepping just out of the world of session beers

[kerneldustjacket]

UHG: Ultra High Gravity...1.101+

Ahhhh,
stepping just out of the world of session beers

Fred, feel free to shift the category numbers upward...

When it comes to OG, I'm the Yin to your Yang. 

[a10t2]

Nonetheless, being a practical person, I think the hypothetical 3-D MLT design isn't.

I definitely think it would work. I'm less convinced that there would be a benefit over more conventional designs.

If lautering speed is the concern, I think all the same concerns that apply to fly sparging would also apply to batch sparging. The absolute best design is probably a false bottom, since you would effectively be able to drain the entire area of the mash simultaneously. And you'd want the shallowest grain bed possible.

As a practical consideration, I have a lautering system that's optimized for fly sparging. (A slotted CPVC manifold.) Using a March pump, I average about eight minutes from starting the runoff to filling the kettle. That probably means each ~3.5 gal runoff takes about two minutes. I don't see any reason to experiment with other designs.

[a10t2]

Makes me wonder if we need to add a few terms to describe gravity:

How about HG: 20-30°P; VHG: 30-40°P; UHG: >40°P?

[richardt]

If lautering speed is the concern, ...[t]he absolute best design is probably a false bottom, since you would effectively be able to drain the entire area of the mash simultaneously. And you'd want the shallowest grain bed possible.

I agree.  I think the 10 gallon round Igloo cooler is experiencing mash bed compaction on the high gravity brews despite the use of a 12 inch x 1 inch SS Bazooka screen in the horizontal position.  That's why I wanted to look for ways to shorten the "wort travel" distance and increase lauter surface area by considering a 3-D lauter design (even though it might not be very practical to implement and use).

As a practical consideration, I have a lautering system that's optimized for fly sparging. (A slotted CPVC manifold.) Using a March pump, I average about eight minutes from starting the runoff to filling the kettle. That probably means each ~3.5 gal runoff takes about two minutes. I don't see any reason to experiment with other designs.

Is the suction from the March pump helping you drain the wort faster?  I am just using gravity and time.  My spigot is 3/8" (5/16"ID), but I am convinced the "bottleneck" during lautering is the grainbed compaction around the surace of the Bazooka screen.  I have to scrape the screen with my mash spoon much like one has to scrape the fine nylon mesh screen on the funnels when transferring wort into the fermenter.  That's what intriques me about Denny's comments regarding the rather short length of his SS braid in his mash tun.  This tells me that there's no grain bed compaction occurring in his system.  His example (using water, i.e., a universal solvent) doesn't quite prove the point to me as it does not reflect the fact that we're actualy straining wort (a viscous colloidal solution) from the mash (a thick "suspension") -- a process which can be quite sensitive to grain bed compaction.
I am looking at two possible practical solutions to the problem of lautering high gravity brews:
1.) Use a rectangular cooler (to decrease grain bed height)
2.) Use a false bottom or CPVC pipe manifold (to increase lauter surface area) on the Igloo.

[euge]

It may be as simple as slowing it down to eliminate your compaction issues. I always went full blast no matter the grist ratio and ran into problems- especially with stiff heavy mashes. Throttle back... no compaction issues. It is what it is. Headache gone.

[richardt]

You're probably right Euge.  I will throttle back next time--at least for high gravity brews on my 10 gallon round cooler.