Who said anything about buying solution?! Don't most of us who trickle make it up ourselves? A set of digital scales already purchased for kitchen/home brewing and bob's your proverbial. And you've not convinced me that Varrox or all that DIY shenanigans is cheaper and it's certainly not easier than my 4 year old plastic syringe. As to disturbance again not convinced - a minute or less and using lukewarm solution and the bees don't stir from their cluster unless the air temp is warm as it was when I did it this new year. Even then there were only a couple of fliers. Not seeing the harm generated by your ingestion theory either. So again as far as I'm concerned oxalic by trickle or sublimation is equally valid. Either way we're inflicting a dose of acid on the bees.