Brixit! Help required with refractometer

[Brewed_Force]

I brewed this 11L (BIAB) AG Porter 2 weeks ago:
1.8kg Golden Promise Pale Malt
200g Brown Malt
200g Medium Crystal
170g Chocolate Malt
150g Flaked Barley
35g EKG 30 mins
10g EKG 10 mins
Crossmyloof Real Ale Yeast

The OG was 15 brix.
The FG tonight is 7 brix.
Going by Brewer's Friend calculator gives an AVG of 6.93% !
I may have seriously underestimated my efficiency (I did a fine crush and squeezed the living daylights out of the bag) or I have ballsed up the calculation somehow.
If the AVG is correct how much water should I add to the bottling bucket to get down to 5% ? (I expect to get 11L into bottles, before adding any water).
I did check that the refractometer was reading zero with water prior to my wort readings.

 

[MyQul]

Liking the pun!

 

[BeerCat]

A refractometer wont work once there is alcohol present so you need to use a hydrometer. 7 brix is about 1035. If the beer is finished your probably closer to 1010.

 

[Brewed_Force]

Hi Beercat, I used the Brewer's Friend calculator which takes account of the alcohol content. The ABV should be about 5.5% according to Brewgr recipe builder. Does my recipe look that much out?

 

[Drunkula]

6.93 / 5 * 11 = 15.25 so add 4.25 litres if you want it 5%. Taste it first. And of course adjust your priming sugar.

That would be about 87% efficiency to get 1.060. That final gravity is way below what beersmith says for those ingredients. It thinks about 1.014

 

[Bigcol49]

Hi!
Take a hydrometer reading!
To take an accurate refractometer reading with alcohol present, you need to work out the correction factor for your particular refractometer.

 

[BeerCat]

This is an interesting article about refractometers here.

 

[Zephyr259]

He's right, ran it through my spreadsheet which has a 2% correction for wort and 15 / 7 brix comes out at OG 1.060, FG 1.011 for 6.4% abv.

 

[Brewed_Force]

If I did get 87% efficiency, is that unusual for BIAB ?

 

[foxbat]

If I did get 87% efficiency, is that unusual for BIAB ?

Not unusual at all if you mashed and sparged well, boiled gently and left little behind in the kettle. 87% is definitely at the high end of usual. Your system must be performing very well.

 

[Duxuk]

I BIAB (heavily modified!) and using your ingredients I would have expected 15 brix ie. 1.061 OG. I'd just use a hydrometer to see where you are now. You've got a few things in there which are going to leave unfermentables so I wouldn't be surprised if your FG is a little high.

 

[Brewed_Force]

Thanks for the feedback chaps, I will probably add a couple of litres of water when bottling to bring the ABV down to something more sessionable. I will dial in 87% efficiency to Brewgr for my next brew and see how that goes.
SWMBO has just bought a set of silicone oven gloves, they will come in very handy for squeezing a hot grain bag!