It is best to have the bottles up off the floor if that is where the transducer (ultrasonic energy generator) is in your unit.
Each item the ultrasonic waves (energy) interact with will cause the wave to give up some of it's energy. The water to basket interface, the basket to water interface, water to bottle interface, bottle to eliquid interface, etc... How much energy is lost at each interface is determined by the acoustic properties of each material. Materials with similar acoustic properties transmit more energy than materials with drastically different acoustic properties. This is known as acoustic impedance mismatch.
Various ultrasonic longitudinal wave velocities (given in centimeters per micro second):
Water - .145
Plastic (generic) - .16
Glass - .579
Stainless .570
As you can see water and plastic have very similar velocities, the energy that will be lost from the water to plastic interface will not be substantial. Water to glass has a larger difference but the energy is moving from a material with slower velocity to a material with a faster velocity, fairly efficient transfer of energy. Some energy is now going to be lost when the wave hits the slower water as it leaves the faster plastic. Next it leaves the slower water (as compared to glass) and enters the faster glass. This process is repeated each time energy moves from one material to another, losing some energy along the way. Now these losses are not anything to worry about as as one wave dies another is coming right behind it at rate of 42,000 per second, assuming your unit is one of the 42kHz units.
If it's really bothering you let me know and we can get deeper by calculating lambda (wavelength) for each material, lambda will tell us the wave's ability to penetrate any given material, then calculating energy transmitted vs energy incident.
My vote is stainless basket set in a manner as not to place weight on the the transducer and glass bottles. If you have plastic baskets and plastic bottles it will still work and the world will not end.
To give you one more thing to worry about; cold water is more dense than hot water therefore, cold water is a better transmitter of ultrasonic energy. Does throwing that in make me a horses ....?![]()
I think I understand this, but it leads me to believe that free floating bottles would lose less energy because the waves would be more consistent around them in stead of bundling them together and having the waves pass through multiple media? I probably made my point as clear as mud, but maybe you catch my drift? Thanks