High gravity, low volume

[Brew4]

Hi,

I am getting a problem where my wort collected in the boiler from the mash tun is constantly of higher gravity than expected.
However, I am getting a lot less liquid, maybe only 75% than expected.

So, it looks a bit like a high gravity brew. I then have to dilute to get to the correct pre-boil gravity.

What could cause this and does it mean a low extraction/efficiency of mash sugars?

Thanks

[lancsSteve]

You're under sparging - put more water through the grains and you'll have more volume and lower gravity. Diluting before boil is no terrible thing though: dilution a LOT easier than upping gravity!

[Brew4]

Thanks Steve.

I sparged until gravity showed 1008

[Eric]

Thanks Steve.

I sparged until gravity showed 1008

Assuming your end gravity figure is corrected for temperature, you might want to try sparging a little more slowly.That will allow time for more sugar to be dissolved into the sparge water. If however you are not short on gravity after diluting your wort, you've no cause for concern, as advised by Steve.

[Brew4]

Thanks.

Could sparge temp be too cold.
I used 80c water to sparge but that goes through a hose.
Then how much more temp is needed to up the grain bed to 76c?

If your sparge water is 80 and grain bed is 66 then probably need higher that 80 water to get bed up to 78, yes?

[Eric]

Thanks.

Could sparge temp be too cold.
I used 80c water to sparge but that goes through a hose.
Then how much more temp is needed to up the grain bed to 76c?

If your sparge water is 80 and grain bed is 66 then probably need higher that 80 water to get bed up to 78, yes?

I've not been inclined to use mash water any hotter than 82C. When fly sparging, I would expect the top few millimeters of the mash to be at sparge water temperature within minutes. Then, as the water make its way down, so the grain temperature will rise, but, I would expect there to always be a temperature gradient of sorts. I don't attempt to mash-out, the wort runs straight into the boiler and as soon as the element is covered, it gets switched on and the enzymes are quickly denatured.
I would think that after initial recycling, about half the extraction has happened before the temperature of my runnings gets back to its initial mash temperature.

[Cazamodo]

On a similar not I just thought I would ask a question on topping up a higher than aimed for gravity beer. I know you can top up Pre boil, but what about after boil? If I loose too much in the boil, Or I'm looking to brew slightly more than my boiler can take, would it deminish flavour by topping up the FV with cooled boiled water to get to the OG I want?

[lancsSteve]

The 'official line' will be you should boil the water and topping up post-boil and post-cool is a bad thing. The unofficial line is tap water ain't that bad - I often have to dilute a little at the end when I find I've lost more to hop absorpton than predictedor lost more to evapouration and am under-length and over gravity. When you make kits you use unboiled water... It's FAR from ideal - boiling the water and cooling would be better but equally it's not exactly the end of the world / inevitable infection. WOuldn't run it through a hose though. ALso depends if your water is nice - if it's heavily chlorinated or otherwise a bit meh (like say London water) then treat and boil.

[Capn Ahab]

Hi,

I am getting a problem where my wort collected in the boiler from the mash tun is constantly of higher gravity than expected.
However, I am getting a lot less liquid, maybe only 75% than expected.

So, it looks a bit like a high gravity brew. I then have to dilute to get to the correct pre-boil gravity.

What could cause this and does it mean a low extraction/efficiency of mash sugars?

Thanks

Hi Brew4,

FWIW I always do a mash out step. If for no other reason than to get the temp of the grain bed up to 75 C as I think this helps with lautering. Sparge slowly is good advice

You can be absolutely exactly precise about brewlength, gravity etc if you don't mind doing a bit of maffs. I started out by using Beersmith, but didn't really understand all the calculations it was making, and didn't know where to adjust parameters to fit my set up, so all my brews ended up wrong on the numbers. As soon as I started doing my own calculations, everything fell into place, and I can now accurately predict what I will end up with at the end of the boil. I learned all the formulae out of Designing Great Beers by Ray Daniels, but I'll try and give you a condensed version here.

First up, what's your evaporation rate? Mine is 11% per hour (pretty fierce), but generally it will be between 5 and 10% on most set ups, and you will have to experiment a bit before you nail it for your set up. I'd suggest starting at 10%, so:

0.1 (10%)/60 (mins) x boil length (I usually do a 75 min boil)

0.1/60 x 75 = 0.125 - this now needs converting into your evaporation factor: 1 - 0.125 = 0.875

Evap factor = 0.875

You can now work backwards from your desired post-boil volume to get your pre-boil volume.

Target end of boil volume: 20 litres

20 l / 0.875 (evap factor) = 22.86 l

22.86 l / 0.96 (shrinkage after cooling) = 23.81 l

Pre-boil vol = 23.81 l

This might be all you need in terms of getting the right volumes - just adjust the equations to your set up and target. Bear in mind I have not made any concession to hop and trub loss, so if you aim to have 20 l in FV it's best to shoot for about 22 l post-boil generally.

If you want to go the whole hog and get a really good handle on what you're doing, start thinking in terms of total gravity units:

20 litres (post-boil) of 1.050 beer = 1000 Gravity Units

20x50 = 1000GU

The reason for using this concept is that it is constant, regardless of the volume of liquid in the boiler at any time.

Next up, what's your mash efficiency? Mine is about 70% for low-med gravity beers, and this is generally a good starting point.

You also need to work out ingredient gravity. This is where it gets a bit messy, cos I had to adjust all Ray Daniel's equations from imperial into metric: RD gives ingredient gravity of pale malt as 1.037 per pound per gallon, or 37 GU lb/gal. To get to metric:

37/0.454 = 81.5 GU kg/gal

81.5 x 3.8 = 309.7 GU kg/litre

I generally use the same ingredient gravity for the entire mash, and adjust the efficiency if there is a lot of speciality malt/grains. This keeps things nice and simple. So:

309.7 GU kg/l x 0.7 (mash efficency) = 216 GU per kilo of grain per litre.

Now remember the total GU? Divide that by 216 to get the amount of grain you need.

1000 GU/ 216 = 4.63 kg of malt

Now you can work out your total water volume when you take into account grain absorption in the mash tun. But that's a variable I haven't quite got to grips with yet, so you can just carry on sparging until you have your pre-boil volume! For a 22 l batch I always treat and prepare 40 l of brew liquor to be on the safe side. Remember to check your pre-boil gravity as well. Using the above example it should be 1.042

1000 GU / 23.81 l (pre-boil vol) = 41.99999

= 1.042. If you haven't hit this, then your efficiency calculation is out. You can either add sugar or DME to bring the gravity up, or add water to lower it. NB. Adding water messes with your volume calculations.

I can also post up strike water calculations for the mash if anyone is interested, but be warned, I (somewhat anachronistically) work in farenheit rather than celcius.

Anyway, hope this helps/is not too dull.

[Brew4]

Sorry haven't replied in a while but thanks capn!
Very exhaustive info there.

Though...still confused as to why I am getting higher gravity but lower volume.
If I add the top up water to the calculations as if I got it from the sparge, it comes out correct gravity and correct volume.
Why am I having to top up and not getting the correct volume in the first place?

Confused

[orlando]

The Capn's response is flawless, incorporate that in your calculations and you will be OK. If you don't fancy the maths, and I'm with you there, get yourself some brew software. There are a number of free ones but if you want to make a relitively small investment but a giant leap in quality then BeerSmith 2 is your best choice.

[Brew4]

Sorry if I'm not seeing the woods for the trees but still confused.

I have worked through Capn's calculations and I am getting the correct gravity/mash efficiency.
It's just that I am collecting less higher gravity wort.
If I collected the correct volume of wort, the gravity would be bang on
i.e. I get 15 litres of 1050 where I was looking for 20 litres of 1038.
I then top up with 5 litres and it gives me the 20 litres at 1038.
It's only the wort volume thats low not the gravity/efficiency?

[orlando]

This is where the calculators in brewing software come into their own. Once you set up the parameters of your equipment and process it will calculate the starting volumes of liquor to ensure you end up with your 20 litres at 1.038. It looks to me that you merely have to alter the quantity of sparge liquor.

Using brewing software won't be an instant fix as you need to adjust it from experience but once you have it tuned it tells you everything you need to know concerning volumes.

[Brew4]

Ok, but I can't just add more water to the sparge.

I am fly sparging so the water runs out when all the sugar flushes from the grains.

I can see if I batch sparged this would work.

The thing is, I am getting the correct efficiency of say, 85%, it's just I need to top up to the correct volume.

How do I get the correct volume with the correct gravity without having to dilute?

[orlando]

Explain that to me? Why can't you add more water to the sparge? Why is it different to a batch sparge?

Efficiency is really unimportant, 85% is no more "right" than any other % what matters is getting the volume right for the gravity required. (software helps)

As for how you get the correct gravity at the correct volume without diluting, is you start with the right amount of water and the right amount of grain, software will help you calculate this, please, please please, get some and it will all fall into place!