You need to look into Venturi effect, I believe.
Assume no magic frothing attachment. Steam is water vapor. It changes to water when it hits the colder milk. Where does the air come from that causes the froth? Logic tells me that when the nozzle is brought to just below the surface, somehow I start to inject air. Can anyone explain the process or point me to a reference? Frothless in Falls Church - Mike. homeroast mailing listhttp://lists.sweetmarias.com/mailman/listinfo/homeroast
Exactly my thinking. Now, the trick is how to position the nozzle to achieve that. All the instructions I"m reading say "place the nozzle just below the surface", but I don't see how that will pull air into the milk. What are you doing up so early? - Mike At 01:10 AM 12/14/02 -0700, you wrote: <Snip> homeroast mailing listhttp://lists.sweetmarias.com/mailman/listinfo/homeroast
Air is sucked past the tip into the high velocity steam jet. Frothing is more effective on cold milk, so make sure you concentrate on frothing first, heating last. Put the tip in the milk, and slowly lower the pitcher until you hear a sucking sound or the sound of cloth tearing. Keep it at that level as the milk rises in the pitcher. It should double in volume. Dan <Snip> homeroast mailing listhttp://lists.sweetmarias.com/mailman/listinfo/homeroast
The best instructions I've read say to start with the tip just below the surface, then lower the pitcher until the nozzle is just above the surface, where you start to hear the characteristic sucking noise. There, air is getting pulled into the steam jet. After you get some foam going you can finesse it to get microfoam, etc. Andy Lynn eagerly awaiting my new check valve, cause the steamed milk just isn't the same if you can't make the espresso to go with it Michael Horowitz wrote: <Snip> homeroast mailing listhttp://lists.sweetmarias.com/mailman/listinfo/homeroast
At 3:13 AM -0500 12/14/02, Michael Horowitz wrote: <Snip> Interesting question. First, as another poster mentioned, there's the Venturi effect: the high-speed jet causes a lower pressure at its outer edge that pulls in air. The second is that the volume of steam is about 700 times the volume of the water it's composed of. So when the steam condenses in the cold milk, it's going to pull a vacuum from the surface. I don't know what the relative contributions are. Best, David -- "To announce that there must be no criticism of the President, or that we are to stand by the President right or wrong, is not only unpatriotic and servile, but is morally treasonable to the American public." -- Theodore Roosevelt homeroast mailing listhttp://lists.sweetmarias.com/mailman/listinfo/homeroast