Batch sparge grain bed channeling

[BenB]

I brewed up my first lager yesterday. I've taken some photos but they're not overly exciting- the grain shot for one is decidedly dull. The usual things occurred (initial mash temp too low, had to liqour back a lot etc etc). Mash pH was targetted for 5.4 and I got 5.5, otherwise not bad.

Main issue was I was low on the OG and efficiency came in at 63% which seems a rather low. The recipe and Beersmith said 1.061 and I got 1.054.

When I drained the wort I noticed the grain bed was not level. When I vorlauf I tend (through habit) to add it back to one particular edge of the MT and I think by doing so I'm disrupting the grain bed and washing the grain to the other side causing an even drain. I'm going to try putting a metal take-away tray on the top of the mash and adding back the vorlauf to that. I suspect I'm not doing myself any favours by adding it back down the side of the mash tun- presumably it flows down the side of the mash tun wall and pushes the grain bed away- therein creating a nice channel to the drain.

How fast should I be draining the mash tun when batch sparging? When I vorlauf I'm opening the tap only a little initially to compact the grain bed but then when draining off the wort I'm opening it fully- would opening it less help prevent channeling?

[BenB]

I should add when I drain I can see the channeling occurring- the wort is flowing round the sides of the grainbed on the "low" side, making a nice cavity in the grain bed as it goes. I should probably have slowed the drain when I saw this happening.

I ground the mash pretty fine- can too fine a grind cause channeling or would that just cause a stuck sparge?

I think I'm losing points in three places

1) under-shot on the pre-boil volume and didn't want to do a third drain so added the extra liquour to the kettle directly (IE watered down the wort)
2) channeling of the grain bed
3) dead-space is 2L which is quite a %age of the batch- one of the things I was testing was a channeled plug which inserts into the bazooka drain and makes it drain from the bottom only- unfortunately the plug had rotated making it top drain So I had to liquour back by 2L (17L up to 19L)

#1 and #3 I can sort. Just trying to resolve #2.

[Matt12398]

One of the main points about batch sparging is that channeling is less of an issue. It's more relevant with fly sparging since you are rinsing through the grain bed. With batch sparging you're mixing the sugars into the batch liqour and then draining.

[Kev888]

Channelling shouldn't matter much with batch sparging. The process involves stirring the grain and liquor/wort for a bit to ensure a good rinsing effect occurs 'before' the wort is run off the grain. (Its very important with fly sparging because the progress of liquor through the grain 'is' the rinsing effect). Its possible that you aren't stirring thoroughly though, leaving some parts of the grain bed relatively unwashed with the new liquor.

For point 1 liquoring back doesn't reduce efficiency as such, though yes the liquor you added could have rinsed some more sugar out had it been put through the grain bed instead of direct to the kettle.

For point 3 the dead space has no effect on mash efficiency, but it does of brew-house and overall efficiency. Its quite important to distinguish the two in order to find out where the problems are occurring; 63% is not great but it would be far worse if that were mash efficiency (thats almost no-sparge territory).

It sounds like there may be several contributors to this, the mash temperature (and possibly sparge temperature?) being too low may also be involved.

[Jocky]

Was 63% the mash efficiency or brewhouse efficiency? Also what is your normal efficiency?

For me the biggest variation by far in mash efficiency comes from the changes in the ratio between grain weight and net liquor (liquor after absorption). i.e. if I get 75% effieciency for a 1.040 beer I'm going to have to add 50% more liquor to get 75% efficiency for a 1.060 beer.

[BenB]

Cheers all! Yes, very good points- I'll have to check when I'm back at home with access to my laptop. I took the number from the "measured efficiency" in the beersmith design page- not sure if that's brew-house or mash- suspect the later. I'll have to dig into the numbers, it may be my mash wasn't so bad but loses elsewhere made a difference as I suspect the design page will look at brew-house.

Normally my efficiency is in the mid 70s. But that's taken from the same place, I'll have to dig out my old BS brew spreadsheets and check the numbers and compare the mash efficiencies (if I'm looking at the wrong thing).

Good points Kev re stirring and channeling not being an issue...... all good info!

Thanks again.

What with the dodgy yeast starter I'm making a right pigs ear of this one

[Rhodesy]

Cheers all! Yes, very good points- I'll have to check when I'm back at home with access to my laptop. I took the number from the "measured efficiency" in the beersmith design page- not sure if that's brew-house or mash- suspect the later. I'll have to dig into the numbers, it may be my mash wasn't so bad but loses elsewhere made a difference as I suspect the design page will look at brew-house.

Normally my efficiency is in the mid 70s. But that's taken from the same place, I'll have to dig out my old BS brew spreadsheets and check the numbers and compare the mash efficiencies (if I'm looking at the wrong thing).

Good points Kev re stirring and channeling not being an issue...... all good info!

Thanks again.

What with the dodgy yeast starter I'm making a right pigs ear of this one

Measured is Brewhouse. If I look at my last brew, I had a 88.4% mash efficiency and 75.7% measured which I am happy with. You can check the mash efficiency in the Mash tab (desktop version) and also as an addable column.

[Matt in Birdham]

Measured is Brewhouse. If I look at my last brew, I had a 88.4% mash efficiency and 75.7% measured which I am happy with. You can check the mash efficiency in the Mash tab (desktop version) and also as an addable column.

I find BeerSmith's treatment of efficiencies to be highly unintuitive, particularly the fact that you can only modify the overall brewhouse efficiency, which is a combination of mash efficiency and losses throughout the system.
What I have done to "fix" this is to remove all losses in my system, apart from my MLT deadspace. I set everything else to zero, so that my "brewhouse" efficiency is now the same as my mash efficiency. Of course you have to factor other losses in by increasing your overall target volume (e.g. if you lose 2l in the kettle, then target 23l instead of 21l). What I also do now is full-volume mashing with no sparge, which further helps with hitting numbers because SG of the finished mash equals pre-boil gravity.

On your channelling issue I agree with the others - it shouldn't really matter, so long as you are giving everything a good stir when you add your sparge water. If you are having mash eff issues then a full-volume mash can help you get a handle on what might be going wrong.

[BenB]

Okay so the plot thickens. Turns out my mash efficiency from the mash page was 87.2%!!! So much for channelling being an issue. Going back it looks like it runs between 76% and 87%. Which is nice. So it's all brew house inefficiency, probably my deadspaces etc.

Interesting!