An essential oil collection is a costly investment. If you have taken the time and made the effort to build a collection, not to mention spent the money on an essential oil collection, you need to store the oil properly so it does not spoil. Though the oils do not go rancid, they can deteriorate and lose their therapeutic properties over time. Oxidation speeds this process. There are some oils that improve with age, such as sandalwood and patchouli, but even those need to be stored properly.
To keep oils fresh and aromatic, store them in blue or amber bottles. Dark glass helps diffuse sunlight and prevents deterioration. In many cases, the oils will come to you in bottles that are appropriate for storage. If oils are sold in a clear container, you might want to buy your product elsewhere. Up to the point of your purchase, the oil has not been protected from deterioration, which means you might be getting a less potent oil. There are a few exceptions to this rule, like base oils. Seeing these through clear containers allows you to check their purity. Plastic bottles are also a bad sign. The oil erodes the plastic, blending the chemicals from the plastic with the oil. This corrupts the oil in much the same way food and beverage is corrupted by the chemicals in plastic containers.
Another consideration is the method of dispensing the oil. Some oils are sold in bottles with rubber droppers. Avoid buying these and opt for bottles with clear inserts that enable users to dispense drops one or two at a time. This type of bottle does a better job of protecting the integrity of the oil, while still preventing spillage should the bottle tip during use.
Once bottled correctly, oils need to be stored in a cool, dark place. Keeping them together in a wooden box helps you stay organized and keeps the bottles from accidentally breaking. The wood also insulates the bottles, keeping them from exposure to warm temperature.