Ok, so I brewed a Milk Stout 2 days ago, Decided I didn't get enough residual sweetness from the lactose last time I did it, so I decided to add it to the fermenter. Fermenter was going strong for 2 days. This morning it was slowing down, so I decided to add the lactose.
I attempted to make a simple syrup with the lactose, but I couldn't get it to dissolve quite like table sugar, it was in solution, but the solution was cloudy. Oh well, its sterile and I let it cool covered all day.
I get home this evening, spray everything on the conical with star san, pull the thermowell, put in a sanitized funnel, and poured the lactose in.
To say I was unprepared for what happened next would be an understatement. FOAM! Lots and lots of foam, think shaking shaking up a bottle of soda and opening it. I reach down and retrieve the thermowell, thinking that I will blow the foam into my blowoff jar. I plug it in. Everything is working for 2 seconds, foam going into the jar, then suddenly foam starts to pour from around the edges of my sealed conical lid, all around!
I give a futile attempt to tighten the lid, then I just stand back, and wait for it to stop, nothing else to do.
In the end, it was entirely foam, lots and lots of foam, but I probably lost about 2 quarts of wort.
What happened? Nucleation sites. The small amount of residual undisolved lactose provided the equivalent of adding a Menthos to a diet coke.
(ref. http://www.youtube.com/watch?v=LjbJELjLgZg)
Note to self, Next time I want to add lactose to the fermenter, do it immediately, before co2 has a chance to saturate the solution.
Hopefully this will help someone out some day.