[silentknyght]

I brewed my first batch using a liquid yeast.  In my haste, I forgot that my only airlock was already in-use, so I rigged up a blowoff tube (see the picture link).  The usual kind of vigorous bubbling that I had noticed with my airlock never occurred.  After one week, when I transferred the batch to a secondary fermenter (glass carboy), I noticed that a great deal of yeast or other matter floating on top.  I used an airlock with the secondary fermenter after the transfer, and this time I did notice a regular bubbling and an actual increase in the amount of yeast or other matter floating on top.  Now, after 4-5 days in the secondary fermenter, the top of the liquid is clear of the yeast or other matter.

http://picasaweb.google.com/lh/photo/dnagMWPkYw2fyvhrFcdSzA?feat=directlink

Is it possible that the pressure of the blowoff tube actually stalled the fermentation?  Or is this kind of activity common?  My primary concern is that the beer doesn't take in a yeasty flavor.  Should I, again, transfer the beer to a new container for the last 3-4 days?

[dak0415]

It's more likely that there was a slight leak in your primary which changed your bubbling rate.  I doubt a bucket will hold enough pressure to stall the yeast.

[tygo]

Whenever I use a blowoff tube setup I hardly every see any bubbling.  It's just not sealed up tight enough.  After you racked it you were likely seeing CO2 coming out of solution, not an additional fermentation.  No need to transfer the beer again just let it set until it's finished up then bottle or keg.

[silentknyght]

After you racked it you were likely seeing CO2 coming out of solution, not an additional fermentation. 

Well, that makes total sense.  My first try with this recipe, the beer did not turn out as well as I would have hoped; we'll see how this one does.

[hopfenundmalz]

The pressure for the blowoff tube set up is negligable.  Yeast will ferment at higher pressure.  Think about a 400 or 800 barrel conical/cylindrical fermenter, where the yeast can have several stories of beer causing pressure on it.

Or there are yeasts that work well under 1 ATM of pressure. 
http://www.whitelabs.com/beer/strains_wlp925.html

Next time press down around the lid, when bubbles start in the blowoff air lock, you have found the leak.

[majorvices]

Did you take a hydrometer reading during any of this process? Hard to say exactly what was going on - you may have had a finished fermentation or you may have transferred before fermentation was finished. Regardless, you would have to be in a sealed, pressure tested, stainless vessel to withhold the kind of pressure you are talking about to stall the yeast.

[bluesman]

Did you take a hydrometer reading during any of this process? Hard to say exactly what was going on - you may have had a finished fermentation or you may have transferred before fermentation was finished. Regardless, you would have to be in a sealed, pressure tested, stainless vessel to withhold the kind of pressure you are talking about to stall the yeast.

+1

Let your hydrometer be your guide in the future.

Likely that you had a leak in your setup.  Pressure will play a role during fermentation but unlikely with your setup.