Ultrasonic mist maker questions

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I'm talking about those ultrasonic pond foggers. I've been experimenting with one to see if I could collect the mist, route it through tubes and whatnot to do a sort of smoke photography. It kind of worked, but after noticing the spurts of water that actually create the mist seemed to have some cool shapes, set about photographing them instead. I uploaded some of the initial shots. These are not great shots, mainly raw from the camera just to show the shapes and "icy" like structures. I had to do it outside so the mist would dissipate in the wind, and also overfill the container to cut down on the amount of mist produced:

Ultrasonic Water Spurts (Picasa gallery Link)

Anyway I was wondering if it would be possible to add something to the water so the same shapes were created but no actual mist was produced, just to make photographing them easier. Turns out several science sites/blogs mentioned soap in the water prevents the mist. The main reason cited is that the soap lowers the surface tension of the water, which somehow stops the mist production. So I grabbed some Morning Fresh dish washing liquid and squirted some in. Nothing changed. Mist was still produced. Even huge amounts of detergent didn't seem to make a difference. Next I rubbed the tip of a finger on some bathroom soap, swirled my finger in the water and the mist stopped being produced almost instantly! Just the tiniest amount was enough to prevent the water breaking into small droplets (mist).

So synthetic detergent didn't make a difference but saponified soap did. Then it can't be to do with surface tension can it? The other thing is with the soap, the water spurts are more "simple". I haven't photographed it yet. But it looks like a single smooth spurt of water unlike the "crystalline" sort of structure like in the photos. Not only that but it seems to rotate around the vertical axis! Why does soap - but not detergent - cause these things? I haven't been able to find an answer anywhere.

Did the soap contain a moisturizer? Even very small amounts of oil will smooth out the surface of water and stop it breaking up, hence the expression 'pour oil on troubled waters'.

Are these gadgets safe, I was thinking of Legionella pneumophila and a whole host of other nasties.

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