How do you "cap on foam"?

I have heard from folks on this forum and on good old Brew Strong podcasts that I should be "capping on foam" when I bottle. I guess I'm not really clear on exactly how you do that. I've brewed a couple dozen batches and I've never had a bottle that I thought went bad from oxygenation or anything else but I want to give my beer every chance to be the best it can be.

So what is the proper technique? On bottling day I clean and rinse my bottles then sanitize using StarSan in my Vetinator. Once I have pumped a few squirts into the bottle, I put it on my bottle tree to drain. They stay there until I'm ready to fill them. Once a bottle is filled, I lay a cap on top - but not crimped yet. After I get a dozen or so filled I go back and crimp the caps on those bottles and then go through the process with the next dozen.

This method seems to work OK for me but there is no foam to cap on - the StarSan foam has drained out. Should I not drain out the StarSan so much or???

That really only applies to bottling from a keg. You pour the pre-carbed beer slowly into the bottle, and then apply the cap on the foam so that you are not leaving oxygen in the dead space.

You will not have carbed beer when bottling from a primary or secondary, so there will be no foam.

OK, I guess I thought I had seen some straight up bottling that mentioned that but I could be mistaken (it gets foggy in my brain some times )

Nope.. you're good.. nice method. Capping on foam, like astro said, applies to keg -> bottle operations. It is the same deal as why you lay your cap on the filled bottle, but don;t cap right away... the disturbed CO2 has a chance to push out the air in the neck of the bottle before you crimp it down. That is what capping on foam is meant to do when you are bottling pre-carbed beer... you fill it till foam comes out a little, lay the cap on top of the foam and crimp it down, as opposed to leaving headspace, like you do when bottling still beer from a bucket.

LarryC said:

So what is the proper technique? On bottling day I clean and rinse my bottles then sanitize using StarSan in my Vetinator. Once I have pumped a few squirts into the bottle, I put it on my bottle tree to drain. They stay there until I'm ready to fill them. Once a bottle is filled, I lay a cap on top - but not crimped yet. After I get a dozen or so filled I go back and crimp the caps on those bottles and then go through the process with the next dozen.
???

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This is how I do it except that I fill all my bottles first before capping them. This has the benefit of letting the priming sugar react with the yeast enough to create CO2 and to purge some of the headspace. The rest of the air in the bottle will get used by the yeast in carbonating the beer.

Just a quick note to those bottling in PET bottles: You can accomplish the same thing by squeezing the sides of the bottle, making the liquid rise to form a meniscus above the rim and cap on liquid. The head space will form in a few minutes and gas will cease to exit the liquid when equilibrium has been reached.

Mister Fizz - FiZZ GiZ