There was a lot of discussion recently among my students about sourcing the dropper bottles for diluting their aromatics.  My Natural Perfumery Institute was the first natural perfumery course that introduced the economical, efficient method of diluting materials to students.  Ever read a "recipe" (aromatherapy term) for an accord or blend that called for 100 drops of labdanum or vanilla?  Very unprofessional!  Thick, pasty aromatics cannot be accurately measured by a dropper.
I prefer my students use the clear bottles so they can see the color of the aromatic. Keeping the bottle out of light rays is important, even for the brown bottles.

I prefer my students use the clear bottles so they can see the color of the aromatic. Keeping the bottle out of light rays is important, even for the brown bottles.

I teach the method of diluting materials in 190 proof alcohol for several reasons: 1.  To make the materials easy to work with.  No more struggling with a pasty "drop" of labdanum. 2.  To save money.  With pricey aromatics like jasmine, orris or boronia, a 10% drop is a lot easier on the wallet than a 100% drop, and will smell the same,  in proportion, to the other aromatics you're working with. 3.  To "open up" the aromatic.  Since absolutes and EOs are so concentrated, sniffing them undiluted doesn't give a true representation of what they'll smell like in an accord or perfume. 4.  To introduce the students to the use of a scale in perfumery.  They learn about tare, grams and that's a huge step up from counting drops, and much more accurate. Another question that keeps coming up about using the droppers is that sometimes the perfumer notices a lot of evaporation through the rubber bulb. I posted my solution to this a few weeks ago on the blog, although I don't follow this practice myself: 1.  Use regular caps on your dropper bottles. 2.  Keep your dropper cap for each bottle in a sealed tiny zip loc baggie, labeled. 3.  When you need the dropper cap, unscrew the regular cap, use the dropper cap, then replace in the baggie after cleaning with alcohol. The use of droppers and scales are just a few of the innovations my students enjoy.  Please consider my excellent distance-learning course for your perfumery studies.  As a dedicated educator, I also maintain this weekly forum for questions from anyone, so I welcome your inquiries about natural perfumery.  Have a great Sunday!