Charlottesville Area Masters of Real Ale

Saturday evening I was brewing a Belgian Dubbel (partial mash recipe that called for a pound of dry malt extract as well as the five pounds of LME, belgian candy syrup and the partial mash grains). When I finished the boil and cooling I was rushed for time so I took a gravity reading, writing it down without paying much attention to the value, pitched the yeast and put it in the basement. The next morning I was going over my notes and realized that I had missed my target gravity by 10 points; then while cleaning up around my brewing stove I found the unopened bag of DME (it was the first recipe I ever used that called for any DME and I spaced when it was time to add it in). By this point my dubbel was already blowing foam out the blow off tube. My solution was that today, with the fermentation no longer blowing the top off, I boiled the DME in 1/2 gallon of water (30 minute boil, no hops) and racked to a clean fermenter adding the additional wort. I've heard of this technique for barleywines and other super high gravity ales so I figured it was worth a shot.

Thoughts??

I think you should be fine.  You boiled the DME so that it would all be in suspension, rather than clumped, which was good (though you could have boiled it for as little as 15 min, as there are some extract brewing practices that regularly do that).  The yeast are still very active, so you are giving them more sugars to work with.  My only concern was that you did not mention cooling the boiling wort.  While it was only 0.5 gallon into 5 gallons, at a very hot temperature, it could raise your fermentation temperature and yeast don't like fluctuating temperatures (though this is more of a problem at the end of the fermentation than the beginning).

Let us know how it turns out.

I did cool the new wort. An ice bath in the kitchen sink had it down to room temperature very quickly. I figured I could get by with a shorter boil, but I wanted to be sure and I didn't mind reducing the volume since I didn't want to increase my total volume very much. The fermentation was was going strong again in less than four hours so I think I am in the clear. We will see how it turns out.

I agree and I think you will be fine.  If you were putting in something highly fermentable like honey or cane sugar, it might cause the yeast to go after those easy sugars (yeast dessert) and perhaps poop out before it had finished the malt (the wort meat and potatoes). 

The only issue I can see might be the space between the height of primary fermentation and when you added the additional malt.  Often brewers making obscenely high gravity beers will keeping adding more malt but will pitch fresh yeast at the same time.  For the activity you are now seeing, it sounds like you are fine but putting new malt into tired (or about to go dormant) yeast can be a problem.  They might not ferment the new stuff and leave you with a higher final gravity and a sweeter beer.

I’m sure it will be amazing.  Bring some to a future meeting. 

Purely for scientific purposes, of course.