Over the past 8 years or so, I’ve experimented with warm water baths, ultrasonic cleaners, stir plates, shaker pads, vortex machines, crock pots and milk frothers. Any method that allows for the introduction of too much heat, light or aeration, can and generally will negatively impact both the nicotine and the concentrated flavours.
Crock Pots and Ultrasonic Cleaners are inconsistent, and introducing heat in this manner is rarely beneficial to flavours or nicotine.
Milk Frothers. Not something I would recommend due to the obvious introduction of air. However, I do use them occasionally when I’m experimenting with recipes, particularly when 75% or more VG is used. Once I’ve settled on a recipe, I don’t use a frother.
Stir Plates. Some models have a heating option, and the only advantage here is for thinning your VG, which can help with the blending of flavours. Unless you’re experimenting with recipes, I’d forgo this as an ongoing option. Not surprisingly, the important thing here is the container for the e-liquid. If it’s an open beaker or bottle, and you’re letting it stir for an hour or more, you’re letting in a lot of air; again, this is generally not a good idea.
Vortex Machines. These can be an option for those not wishing or physically unable to shake their mixes. Due to the fact that they blend high VG mixes in a matter of seconds, and that heat and aeration are not an issue, there is justification for this option. I’ve used them before and they do a great job, the issue, however, is that most quality, affordable models only handle a 30 ml bottle.
Of all the hardware methods, a Vortex is my favourite. They’re fairly expensive though, costing close to $250 delivered.