...and as a followup, how much should I care?

I've always used krausen presence as a rough indicator of fermentation vigor in primary. But my current batch hardly has any, with a few days at never more than a half inch. It's definitely going, with a bubble every few seconds from the airlock. However, it was a slow start (almost 24 hrs before activity) and it's never felt like it was going too strong.

But it got me thinking: what exactly is krausen, and how reliable an indicator is it of fermentation health? My hope is to ask in the more general sense, as opposed to trying to debug this specific batch.

As a matter of interest, this is what I did:

• 1.5 gallons (ferm vessel is a 3-gal carboy)
• 2 lbs light DME
• 1 oz Cascade - 30 min @ 160F
• 2/3 oz Cascade - 15 min @ 160F
• US-05 (a full packet)
• current temp is about 65F

Some possibilities I can think of for why krausen is less on this batch:

1. No boil = proteins coagulated differently than I'm used to
2. I poured the wort through a strainer instead of siphoning
3. Light & simple wort = less proteins than I'm used to?
4. Slow start = bad yeast?
5. ...though some people say US-05 can work slowly in general
6. Yeast is a living thing, thus every batch behaves differently, RDWHAHB.

...and as a followup, how much should I care?

I've always used krausen presence as a rough indicator of fermentation vigor in primary. But my current batch hardly has any, with a few days at never more than a half inch. It's definitely going, with a bubble every few seconds from the airlock. However, it was a slow start (almost 24 hrs before activity) and it's never felt like it was going too strong.

But it got me thinking: what exactly is krausen, and how reliable an indicator is it of fermentation health?

As a matter of interest, this is what I did:

• 1.5 gallons (ferm vessel is a 3-gal carboy)
• 2 lbs light DME
• 1 oz Cascade - 30 min @ 160F
• 2/3 oz Cascade - 15 min @ 160F
• US-05 (a full packet)
• current temp is about 65F

Some possibilities I can think of for why krausen is less on this batch:

1. No boil = proteins coagulated differently than I'm used to
2. I poured the wort through a strainer instead of siphoning
3. Light & simple wort = less proteins than I'm used to?
4. Slow start = bad yeast?
5. ...though some people say US-05 can work slowly in general
6. Yeast is a living thing, thus every batch behaves differently, RDWHAHB.