I accidentally used 6kg's of grains (Simpson's Ale base malt & Caraaroma) for a 10 liter brew, 10grams of Mangrove Jacks Empire Ale Yeast and 75grams of Hops (Columbus,Centennial and Yellow submarine). I am in day 3 of a 14 day fermentation process after which I plan to bottle and store for at least 2months. What will the implications be for using excessive grains?
The first problem is that the Mangrove Jack's Empire Ale yeast has an alcohol tolerance of only 8%. Using some beer recipe software, the amount of malt you used would lead to an alcohol percentage of 15%. Which means that your yeast will stop halfway the fermentation.
Second, the amount of hops is not matched to the original gravity obtained by using 6kg malt. Your IBU will be lower than for the original beer.
You could probably move your beer to a larger fermenter and dilute it. The problem here is if the original yeast will restart, but I suppose you might make an active starter with the same yeast to get the fermentation going again. Note that if you do this, the alcohol level will dilute to 4% and then increase again.
The problem with dilution is that this also dilutes your hop bitterness, taste and aroma. You could try to adjust this by boiling hops in water and then use this to increase the bitterness. Boiling hops in water has a better efficiency than in sweet wort.
And then you can adjust hop taste and aroma with a hop tea.
If you work clean and careful, I think that this should not be a problem. There is ongoing fermentation, and there is already alcohol, so if you clean your larger fermentation vessel, I would say that the risk of contamination is minimal.
I agree with chthon. In any case, the results will be different than the orginal recipe.
One thing that is affected by doubling the malt is the hop utilization. Hop utilization varies depending on the pre-boil gravity : http://howtobrew.com/book/section-1/hops/hop-bittering-calculations
Hopefully, you used enough water in your mash to get a good conversion? A gravity reading at any point would give you important information on what is going on.
Since you had enough grain to make a 20L batch, you could double the water and perform dry hopping or hop tea to compensate. Otherwise you could end up with unfermented sugar that will sweeten you beer. Note that even if the yeast has an alcohol tolerance of 8%, it doesn't mean it will stop at 8%, it could reach 9% or 10%.