Low OG

[monty1]

I brewed up my Citra single hop pale ale - the one I posted my recipe to here viewtopic.php?f=4&t=1206)

My OG came in at 1.040 rather than the estimated 1.053.

I ended up with 10 litres as per the recipe (5 litre wort with additional 5 litres tap water due to pot size) and the recipe otherwise went pretty much according to plan. My mash temperature was an average of 66 degress but was with +/- 3 degrees.

What did i do wrong to get a low OG and is there a way to fix it? Did i not get enough sugar out of my grain - I stirred the mash every 5 minutes or so and sparged too.

[Jeltz69]

I suspect that its a mash issue. Not getting a good efficiency.

I take it that you are still doing BIAB? What was the starting and finishing temp of the mash and how long did you mash for?

[vacant]

Given "66 degress but was with +/- 3 degrees", I'd guess the starting mash temp was 69, finishing at 63. Unless the mash was for less than 30 minutes, I'd be surprised to see efficiency drop from an expected 70% to 53% due to BIAB mash technique, there's not really very much to go wrong lifting a bag out. However, I've had BIAB vary from 65% to 75% which was probably due to the crush so maybe 70% is too high for your current sack. 65% to 53% is still a big drop though.

If your 10 litres @ 1.040 are precise, are your scales accurate? Did you weigh the grain correctly ? I use 500g kitchen scales and once brewed with eight scoops of MO rather than the recipe's nine by mistake.

[monty1]

Yes this is still BIAB. Starting temp was about 68, mash for 60 minutes controlling the temperature as best I could on the gas burner. It slipped up or down a few times but was rarely outside of 3 degrees each way.

To be honest I didn't weigh when I used a full bag (so where I knew i needed a kilo, i used a 1 kilo bag) and only weighed where i needed a partial bag and used a good set of digital scales. Thinking about now I should have weighed, but would the slight amount you probably get over in a bag really make this kind of difference?

Do i just need to mash for longer? Should I mash until i hit my target OG?

[Jeltz69]

My advice would be to get the water up to 70-71°C put the grain in, check that its OK temp wise. Then take the pot off the hob wrap it in a duvet or sleeping bag and leave it for 90 mins.

Trying to control the temp on burner is very hard compared with trying to keep the heat in with insulation.

[steve crawshaw]

My advice would be to get the water up to 70-71°C put the grain in, check that its OK temp wise. Then take the pot off the hob wrap it in a duvet or sleeping bag and leave it for 90 mins.

Trying to control the temp on burner is very hard compared with trying to keep the heat in with insulation.

For my system (50L mr. lard mash tun) 70 - 71 would be too low. My strike water is at 77C and this gets me to 66C mash every time. YMMV.

[Jeltz69]

Indeed lots of factors come into play but I would be surprised if the strike water needed to be that high with BIAB. As the single vessel is heated with the strike water in you don't get the same level of heat transfer to the tun and the greater ratio of water to grain reduces the effect of the temperature of the grain.

Obviously if the grain is stored at very low temperature then the strike water will have to be higher, but if its about room temp I'd still dough in @ 70°C and see what happens. Its easier to heat than cool in that situation.

[vacant]

For my system (50L mr. lard mash tun) 70 - 71 would be too low. My strike water is at 77C and this gets me to 66C mash every time. YMMV.

Nic's temps are right for BIAB. Typically if 12L water @ 78C drops to 66C with 5Kg grain (12C drop), then 34L water for a BIAB is roughly three times the volume so will have a third of the temperature drop of around 4C so 71 - 4 = 67.

[monty1]

It's just occurred to me that I took my OG at around 33 C rather than 20 C

I've used an adjustment calculator (hbd.org/cgi-bin/recipator/recipator/hydrometer.html?16484400)

which corrects my reading to 1.044

So, still out but not quite as much

When I come to measure FG, should I heat the test liquid to the same temp I took OG at?

[Jeltz69]

I just take note of the SG & Temp and plug it into the calculator on the homebrew forum to give me the corrected reading. My hydrometer is calibrated @ 20°C.