Hitting really low gravities!

[RdeVjun]

Agree with Mark, Droopy & others, the pot is a restriction and some recirculation should help, be it manual or pumped. Where the 'BIAB' structure, in your case the 19L pot, doesn't fill the kettle there's much dead space that doesn't allow for much contact between all of the water and the grain, while all the mash stirring on earth will have little if any impact if it is constrained in a limited volume. However, a mechanism to achieve the same ends as regular BIAB should compensate, ie. move the water through the grain.
I had this problem with a largeish cake rack and undersized bag once, some recirculation seemed to fix it.

 

[checkers]

Not efficiency related..but.. How do you lift that pot out?

2 irwin vice grips.. One each side
I lift it out, put a cake rack on top and then sit it on top of that and sparge.
Works a treat

 

[checkers]

Just punched some of your numbers into the BIABacus and it doesn't agree with beersmith. In fact to get 1.050 from your grain bill I had to adjust the efficiency up to about 75%.

I guess the first question is what efficiency are we talking about. Mash efficiency or brew house efficiency?

If I read your posts correctly you are leaving 8L or about that in the kettle below the tap? If so that will drop brew house efficiency. Although knowing your mash efficiency will be of the most benefit to it is worth taking a preboil gravity measurement.

Another thing is that you got 22L at 1.040 when you expected 20L at 1.050. There is a direct relationship between volume and gravity. V1xG1=V2xG2

So 22x40=20xG2, G2=44.

In this case the extra volume accounts for 4 gravity points.

So there's a few options to hit your targets. If you are not recirculating it might be worth trying a brew with a cheap bag, you will get more transfer between the grain and water than with the pot.

Do a 90 minute mash, the extra time does make a difference.

Do a mash out, raise temp to 75C and hold for 10-15 minutes before pulling the grain.

Measure everything so you know gravity and volume at different points in the process. This will help you understand what is going on in terms of losses to grain absorption, boil off and trub and help you tune in your system.

At the end of the day you still made beer so don't worry too much about he numbers!!

This post was written over a couple of hours with kids going nuts so apologies I it isn't that coherent!

Thanks a lot mate,
A lot of good advice in there.
I'll print that out and start the process of elimination

Where you talk about the 22L and the 20L giving different gravity points?
If I didn't add any water wouldn't 1L of wort have the same gravity reading as 20L?
Just thinking if there is "x" amount of sugar extracted it would be the same whatever volume?

 

[checkers]

Just a couple of points that might help
72oC isn't a mash-out, a mash-out is designed to end enzyme activity and improve the wort fluidity, try 78oC
Calculate your strike water temperature, don't guess and make sure you have a reliable thermometer.

You need to be getting the sugars out of the grain and into solution, you have a tap there so just draw off a couple of litres of wort and return it to the top of the grain bed, doing that regularly throughout the mash will stop the extract just building up in the grain pot and blocking more extract from coming into solution.
Your mash in L:G is over 5:1, but in the grain pot your 5.3Kg of grain is in at most 12L of water, effectively a L:G of 2:1 or so, that will cause all sorts of problems - I'm guessing a small pump would be a really good idea.
Mark

Yea I'll go and get one through the week..
I did draw out a fair bit and dump it on top when I was ramping up the temperature as I knew the water around the element would be loads hotter than in the top of the pot..
I'll try a bag and see what happens.

 

[MHB]

If you put 1 teaspoon of sugar in a 500mL cup of coffee, taste, then add another it would be twice as sweet.
if you drank half the cup then added a teaspoon of sugar to the remaining 250mL, it would be just as sweet as the full cup with 2 sugars.
Ultimately sweetness is a function of the amount of sugar per unit volume.

As brewers we measure the amount of sugar (Extract) in two ways S.G. and degrees Plato (Po)
If you took 100g of sugar, then added water to make 1000g (1Kg) it would be a 10% Weight for Weight (%W/W) sugar solution or what a brewer would call 10Po
The SG would be very close to 1.040, but you wouldn't have 1 litre, 1 litre of 1.040 would weigh 1.040Kg but 1Kg of 1.040 would only be (about) 961.5mL
The equation contrarian used can be expressed in different ways C1V1=C2V2 is the form I use mostly (studied chemistry)\
Concentration 1 X Volume 1 = Concentration 2 X Volume 2
You got 22L at 1.040 and you were expecting 20L

Just one thing you have to really watch is the 1.000 part of the 1.040 - it isn't there
It's what we call non-unitary as its telling us that the liquor in question is 1.04 times heavier than water, you could just use the 0.040 or call it 40 points or work in Plato you will get the same answer either way - just leave out the 1.000 part.
in Po 22*10=20*C2 or (22*10)/20=C2 C2=11 converts to 1.044
in S.G. 22*40=20*C2 or (22*40)/20=C2 C2=44 (or 1.044 if you prefer)
if you try that with the 1.000 bit in you get (22*1.040)/20 = 1.144 seriously wrong!

If you want to switch between S.G. and Plato SG = (4*Po)/1000 + 1 (roughly)
Mark
Edit
if you want to get really picky.
Plato = 135.997*SG3-630.272*SG2+1111.14*SG-616.868

 

[contrarian]

That's a better explanation than I could have given.

The point being that if you were expecting 20L and got 22L you either ended up with more wort than you expected or are not calculating losses correctly.

This is why measuring volumes an gravities at key points is so important. Until you know how much volume you are losing to grain absorption, evaporation and to trub any attempt at calculating efficiency is just a stab in the dark and you will always struggle to hit your numbers.

Copying recipes from others is also hit and miss as often critical information to enable replication is missing such as volume or efficiency.

It's a lot to take in but I would bet that by the time you have 10 brews under your belt you will understand your system and be hitting your numbers without really thinking about it!

 

[checkers]

Thanks everyone for your help. I've learned a lot and got a lot to get my head around