Colored Glass Bottles and Essential Oils 10 years ago

Many people ask me all the time if its really necessary for essential oils to be stored in colored glass bottles. My preference is to store the oils in clear glass because color analysis is important to me and I want to be able to clearly see the color of the oil. The truth is that most essential oils are photochemically inactive in the visible region but do have some reactivity in the ultra-violet (UV) region of the electromagnetic spectrum. Since UV light of high enough energy to cause photochemical reactions in most organic molecules is absorbed (not transmitted) by normal glass, regardless of color, most of the time it really makes little difference if the oils are in clear, brown, blue, green, purple or whatever color glass. Of course there are a few exceptions, as with the chamazulene containing oils (blue chamomile, blue yarrow, blue tansy, etc.) that you would not want to store in colorless bottles for long periods under heavy lighting conditions. This is because chamazulene has strong absorption in the VISIBLE region of the spectrum (thus the intense dark blue color of these oils) and so it is the lower energy visible light and not just UV light that can significantly effect these oils. As a general rule, if the liquid is intensely colored then thats telling you that there is significant activity in the visible region and normal light can effect the product since clear glass is obviously transparent to all frequencies of the visible spectrum.

But even so, photochemical degradation is not really the biggest threat to essential oils. Of more concern is thermal degradation and reaction with oxygen, these are the biggest enemies of essential oils in general. For this reason you should really be more concerned about refrigerating oils like citrus and the chamazulene containing oils because they are more susceptible to thermal degradation than other oils. Furthermore, since oxygen plays a big role in decomposition, you should keep airspace in the oil to a minimum. I recommend as a general rule that once the oil container is half full then its time to transfer the oil to a smaller bottle, this will significantly extend the useful life of the oil. If you want to see how air affects oils then try putting some orange or grapefruit oil in a bottle and only filling it about 1/10 the way full. Come back to the oil about 6 months later and dip a scent strip in the oil to evaluate it and you will notice a drastic difference in the odor. Many times viscosity will also change because the oxygen can cause polymerization reactions making the oil a thicker consistency.

So, in summary, if you just take extra measures to keep the airspace to a minimum and the temperature at 75 or below (even lower in the case of citrus and other oils more susceptible to thermal decomposition) then you can keep the oils smelling nicer for longer periods as well as extend their effectiveness and these two things will contribute far more the preserving the oil than any colored bottle will do.

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