Tip: Utilize Your Erlenmeyer's Full Capacity

I read a few threads about starters in Erlenmeyer flasks that indicate you shouldn't try to make a starter the size of the rated volume (top graduation) of the your flask... lest you want to be mopping krausen off your stir plate and table.

Several threads take this a bit farther, recommending the largest starter 25 - 50% smaller than the rated volume. For a 3000 ml flask, this would mean a starter in the range of 1500 ml - 2250 ml.

There's an easy way around this. And it's not to buy the next larger flask.



One drop of FermCap-S per 1000ml of starter will minimize or even prevent krausen formation. Not only does this allow you to utilize the full volume of your Erlenmeyer, but it also increases the rate of gas exchange at the liquid/air barrier.

Here's an example of taking it to the extreme (3450 ml in a 3000 ml flask):



Note, I wouldn't recommend taking the flask past it's rated capacity because the liquid/air barrier size decrease. That is, unless you can pull a vortex with your stir plate. I promptly turned mine up after this picture to do just that.

Thanks for reading!

Strains Tested Successfully:

WLP001 / WY 1056 (US-05)
WLP007 (WY 1098 / S-04)
WLP029
WY 1214 (WLP500)
WY 1968 (WLP002)
WY 1450


Use Caution With:

WLP300 (WY 3068). Even with Fermcap, this yeast still builds a (less) impressive krausen, even with very heavy stirring. I wouldn't go past the rated volume with this strain.

That is impressive. I really need to buy some femcap...

Right after I took the picture, I added 3 drops of FermCap and turned up the stir plate to form a vortex.

The krausen dropped in under a minute and stayed gone for hours 23 thru 36. As soon as it dropped, I sanitized a butter knife and pushed what was clinging onto the glass back into the liquid. No sense in wasting viable cells, right?

thadius856 said:

[...]Not only does this allow you to utilize the full volume of your Erlenmeyer, but it also increases the rate of gas exchange at the liquid/air barrier.[...]

Click to expand...

That seems counter-intuitive, given that the surface area of that wort in the flask pictured is so small. Other folks stress not to fill the flask so high to preserve surface area to enable O2 take up as much as preventing blow-out...

Cheers!

day_trippr said:

That seems counter-intuitive, given that the surface area of that wort in the flask pictured is so small. Other folks stress not to fill the flask so high to preserve surface area to enable O2 take up as much as preventing blow-out...

Cheers!

Click to expand...

This is true. And that's also why I recommend not going past the rated fill unless you can pull a vortex. Fortunately, most stir plates can. The one pictured did it at 1500 rpm with a 1" stir bar. I'll bet I could pull a vortex at the pictured fill at 800 rpm using a 2" stirbar.

With a vortex at the pictured fill level, I have more surface area than at half full without a vortex. And the liquid is moving a whole lot faster too.

The oxygen transfer on a flask that full must be horrible.

Vigo_Carpathian said:

The oxygen transfer on a flask that full must be horrible.

Click to expand...

It's probably best that I point this out again in the OP...

thadius856 said:

Note, I wouldn't recommend taking the flask past it's rated capacity because the liquid/air barrier size decrease. That is, unless you can pull a vortex with your stir plate. I promptly turned mine up after this picture to do just that.

Click to expand...

But again, if you can hear air hitting the stir bar, it's pretty safe to say you have plenty of contact area.