Yesterday I brewed a 10G batch of a Bell's TH clone. I harvested yeast from three dregs of Bell's Amber earlier in the week. I started with 300ml and stepped up to 500ml and had about a 16th inch of yeast at the bottom of the quart jar.
Against the advice of my LHBS guy I still pitched one of my 5G primaries with the slurry. The second primary was pitched with S04. I know, I know. I should have went slower, stepped it up several more times, and probably under-pitched. Poor planning and lack of knowledge on my part.
My LHBS guy said it was hard to harvest yeast from bottles and that I may get wild yeast instead of the intended yeast. Perhaps he is trying to sell more yeast. He said to smell the yeast to determine if it was good. Well, I'm not sure I would be qualified to sniff out a bad yeast unless it was foul. Regardless, it did not smell foul and I pitched it. I figured if it did not take off I would over-pitch S04.
Well, 12 hours later the S04 primary was off and going strong. The Bell's yeast primary was going about one bubble a minute.
My questions are;
If I under-pitched will the yeast propagate to the colony size needed to do the job?
What signs should I look for that something may not be progressing as hoped for?
Is there anything else I should do to help the process? i.e. Nutrient, energizer, etc.