Every now and again we get asked out liquid dosing of our BSP vitamin supplement which is done using a dropper.
The 50ml and 100ml bottles have different droppers and the droppers changes about 4 years ago. At that time the nozzle aperature was bigger and the drop was bigger, so the doage was different. The viscocity of the product also changed and we found that this also affected drop size.
Lost the will to live yet??
I personally measured drops, number of drops per ml from a range of nozzles. I found that apertures varied, product viscocity varied, including with temperatures (its thicker and less drippy fromm the fridge, than from the warm window sill).
Still with me??
I then looked at the other end, what we knew birds and animals need (not a massive amount of useful data, but growing), and what is in their natural diet (varyting through the year and with storage in the home - fridge, outhouse, wherever).
I factored all of these issues in via long and boring spreadsheets and then factored in the day to day variation in fluid intake (depending on the moisture contenet of the rest of the diet).
Sum of all this was that the drop size varies a bit, the animals intake varies a bit, but natural systems correct themselves give a chance and the birds or animals do very well with what we do.
So keep using BSP, we do care. We give you a very good, sound product and we do even think about drop sizes.