Adding DME after initial fermentation

[Horners]

Ironically given my previous post on liquoring back, the other batch I brewed that weekend (an attempt at Darkstar's Hophead) was mashed far too high (didn't adjust strike water for the heatwave or lower than normal grain bill) and suffered poor efficiency. After 8 days this was looking like finishing up at about 2.6% and whilst it tasted amazing out of the FV in a hasty move I mixed up 500g of extra light DME I had lying around in a couple of litres of water and slung it in the FV.

Was this inadvisable?

How do I calculate the additional ABV? I guess that by knowing the OG that went in the FV from the mash, I should be able to calculate a theoretical OG as if I had put the DME in at the start? FWIW the OG was 1036 in 20L.

Any thoughts or comments welcome.

 

[Covrich]

It is only an estimate but I think 500grams of DME in 20l will add about 0.9%

What temp was the mash at?

 

[Horners]

Mash was 71C IIRC and very thin as I had measured and treated water the night before without considering that my grainbill was smaller than normal as I was aiming for 3.8% to make a nice session brew as per the commercial version. Seems to be less margin for error with lower ABV beers.

 

[foxbat]

The high temperature of 71C was almost certainly the reason it finished at 1.016. At least you know now what attenuation you get from whichever yeast it was when you mash at 71.

 

[Horners]

The high temperature of 71C was almost certainly the reason it finished at 1.016. At least you know now what attenuation you get from whichever yeast it was when you mash at 71.

Indeed although how often I will mash at that temp or use a 50 50 mix of Notty/ Sa05 is unknown.