Ask Mr. Wizard

Using leftover wort to prime next beer


Ken Durigan • Hainesville, Illinois asks,

I have been an all-grain brewer for the past two years. In the bottom of my boiling kettle, I always find a fair amount of hop trub mixed with wort, which I separate from the main primary. Just for grins, I dumped all but the thickest of this “mud” into a sanitized half-gallon growler and loosely put on the cap. By the next day, all of the trub had settled to the bottom of the growler and there was about a quart of clean wort on top. I siphoned this into sanitized bottles, then placed the bottles in 180° F water and held it there for 20 minutes. I then capped the bottles, let them cool and stuck them in the fridge. The sterile wort has a gravity of 1.113. I would like to use this wort to prime my latest batch of barleywine, but I don’t know how much to use. I don’t want bottle bombs, nor do I want undercarbonated brew. How much should I add in a 4.5-gallon batch to give the proper carbonation level? The specific gravity of the barleywine is 1.018, if that makes a difference. Also, is there any reason to not use the “nasties” from the boiling kettle in the way I have described? I have done this for the past few batches, so I now have a growing supply of this wort for yeast starters and for the occasional bottling that I do.


Priming with wort is very tricky, because wort is not completely fermentable and its fermentability varies from batch to batch. Breweries that bottle-condition with wort determine the fermentability of each lot before
Response by Ashton Lewis.