Too "thin" mash?

[Toxxyc]

Good morning ladies and gents,

So yesterday I brewed my second ever all-grain beer. It's been a while since my low-ABV (that came out very "meh") since I became a father and all that, but I tried yesterday.

Anyway, my recipe was pretty simple. I planned a 14l batch, using 2.3kg of grains. I hoped for a 1.04 OG post-boil but undershot severely. My mash efficiency came in at around 50%, which is a lot worse than I had hoped. I was wondering if you guys could comment on my method and see if it's maybe due to the "thin" mash I had? I used:

1kg Vienna malt
1kg Pale malt (like 2-row)
0.3kg CaraMunich II

Mashed in 15l of water, strike temp 70°C. I mashed for an hour at 66°C. When I got the wort out there was a bit less than I expected so I did squeeze the bag pretty hard to get the wort out. Post-boil gravity came in at only 1.032. The colour and taste and bitterness is all spot on and perfect for me, so that I'm not worried about, but I ended up with less wort than planned at a lower OG.

So my question is - Could the watery mash cause this? Should I next time reduce the water and increase the grains? I'm planning on increasing the grain content anyway next time (maybe add another 1kg of Vienna), but should I try to reduce the water amount as well? I saw lots of "quarts per pound" of grain numbers, but plenty of guys said it doesn't really matter, so I thought little of it and just mashed with lots of water from the get go to avoid a sparge session (space is an issue).

Smell from the fermenter is amazing, by the way, so I'm not unhappy with the batch. I just want to figure out where I went wrong so I can fix it come next batch.

 

[Gnomebrewer]

A no-sparge mash (very thin) will have lower efficiency than a mash with a sparge, but should still be much higher than 50%, even without squeezing the bag. A no-sparge BIAB with a squeeze should get you better than 70%, quite possibly a lot higher.
A few things that could cause a problem:
Grain crush (#1 efficiency culprit). Whole (uncrushed) grains just don't work. What did your crush look like? Are there many whole grains?
Water. If your water is very high in alkalinity, your pH won't be right. I'll look for a Pretoria water profile and post back if I find one.
Temperature: Have you calibrated your thermometer?
Hydrometer: Have you calibrated your hydrometer? Your efficiency might be better than you think!

Whatever the issue, you can help efficiency by have a 15 minute rest at about 70 to 72C. Hold back some of the mash/strike water and use it for a boiling water infusion after the main mash rest. It helps finish things off, more due to extraction of starches that can be stubborn at lower temps rather than the actual conversion.

 

[Gnomebrewer]

Here you go. Low Calcium (19ppm) and moderate alkalinity (70ppm bicarbonate). You should definitely start using some Calcium chloride; about 2tsp in a 14L batch would be good. Some acid would help things as well, but shouldn't be responsible for the very low efficiency.

 

[Toxxyc]

Yeah the grain crush is fine. It's crushed for my by the brew shop I buy my grains from, and they have some good mills. It's the same as last time. I had no whole grains, and the whole crush was great.
Water isn't too alkaline. I used tap water, yes, but I doubt it'll be THAT big of a difference, would it?
I used a no-contact thermometer that's supposed to be accurate to 0.1°C, since it's also used to measure fevers and whatnot. I've double-checked it with two other "manual" thermometers, and it's spot-on accurate.
The hydrometer is calibrated to 20°C wort. I measured the wort at 22°C, so slightly up, and I adjusted the OG for temperature. When the wort was cooled down to 20°C I measured again and got the same reading.

I THINK, for now anyway, that the thermometer might be correct, but I THINK that it might be reading incorrectly by taking the surface temperature of the wort/mash. I'm not 100% sure, but I can only imagine that that's the issue I have. I'll have to invest in a better thermometer before the next brew.

EDIT: Thanks for that, I'll definitely look into it. It's strange though - with my previous batch I made I got 79% efficiency with the same tap water

 

[Gnomebrewer]

If you are full volume mashing, give the mash a thorough stir at the end of the mash, then measure the gravity before you remove the grains. Use the spreadsheet below to calculate your mash conversion efficiency. If it's not AT LEAST 90%, keep mashing - preferably at a higher temperature around 70 to 72 (boiling water infusion or heat on stove top etc.).
http://braukaiser.com/documents/efficiency_calculator.xls

 

[Toxxyc]

Yeah I stirred the mash twice during the mash, but I'll give it a test next time before I stop mashing. I can't waste that much grains each time, it doesn't make sense. It's cheap, yes, but I hate wasting.

Like, I DESPISE wasting.

 

[RM-MN]

Yeah the grain crush is fine. It's crushed for my by the brew shop I buy my grains from, and they have some good mills. It's the same as last time. I had no whole grains, and the whole crush was great.

If you only got a 50% efficiency I doubt that the grain crush was fine. They may have excellent mills but they are set to accommodate all brewers, not just you. Bite the bullet, get yourself a Corona style mill. Set it as tight as it will go and try another batch. I've never had efficiency below 80% even with full volume, no sparge.

 

[Toxxyc]

If you only got a 50% efficiency I doubt that the grain crush was fine. They may have excellent mills but they are set to accommodate all brewers, not just you. Bite the bullet, get yourself a Corona style mill. Set it as tight as it will go and try another batch. I've never had efficiency below 80% even with full volume, no sparge.

They also milled my previous batch of grains, and on that batch I got almost 80% efficiency. I think something else was amiss here, and the more I think about it the more I honestly think it was the temperature of the mash.

 

[Toxxyc]

OK so it seems all is not lost at all. I may have low gravity, but the smell from that fermenter is incredible. There's hope!