Storing Bulk Fir Oil Without Letting It Go Stale
Bulk oil does not go stale because it is big. It goes stale because the container keeps getting opened. A 25 lb container opened every week lets in more air, over more months, than the same oil split into sealed bottles on day one. The fix is almost boringly simple: keep the big container full and closed, and decant only what you will use soon into smaller amber glass.
Fir Needle Essential Oil
Our own Fir Needle Essential Oil, in sizes from 0.5 oz to bulk.
From $10.99
Shop Now →The arithmetic of headspace
Oil is bought by weight and stored by volume, so start by converting. Using the relative density on the Certificate of Analysis we publish, 0.924 at 20 C for one batch, a pound of our fir needle oil is about 491 ml.
| Size | Volume | US gallons |
|---|---|---|
| 1 lb | 491 ml | 0.13 |
| 5 lb | 2.45 L | 0.65 |
| 25 lb | 12.3 L | 3.24 |
| 400 lb | 196 L | 51.9 |
Now picture the weekly pour. Every time a pound leaves a 25 lb container, 491 ml of fresh air moves in. By the time the container is half used, the remaining oil sits under about 6 L of air. The last pound has spent the most months under the most air, which is the opposite of what you want, since the oil you use last should be as good as the first. This is arithmetic, not a measured result, but it explains why the instructions on oil containers so often say "full".
Decanting early turns it around. A pound fits a 500 ml amber bottle with only a little air above it, and the bottle stays sealed until you start it. Twenty-five of those bottles carry the same oil with one air exchange each, instead of twenty-five exchanges in one big vessel.
What air does to conifer oil
Conifer oils are mostly terpenes, and terpenes react with oxygen over time. The Tisserand Institute lists heat, light and moisture as what speeds that along, notes that most essential oils keep well for at least one to two years before oxidation starts to take effect, and says refrigeration about doubles an oil's useful life (Tisserand Institute). Oxidized terpenes have shown up as skin sensitizers in patch-test work: in a study of 1,511 dermatitis patients at six European centers, air-oxidized linalool reacted in 1.3 percent (Matura et al., 2005). Linalool is not a main fir compound, so treat that as a general illustration of why a stale container is worth avoiding, especially if the oil will end up in something people put on their skin. Our own advice matches: tightly capped, cool and dark, and we say typically one to two years for conifer oils.
How to decant
- Decant in blocks. One working bottle per month of use beats a bottle per week. The sums for sizing are in our per-batch guide.
- Fill each bottle to the shoulder, cap it tightly, and write the date and lot number on the label.
- Reseal the big container straight away. Resist topping it up from working bottles, which would mix older oil back into the lot.
- Keep everything cool and dark. Our oil goes into amber glass in every size. If your bulk container is plastic or metal, ask your supplier what it is made of before storing oil in it for months.
A word on flammability and paperwork
Essential oils are volatile, aromatic liquids, and a drum of any of them deserves care: keep it away from heat and ignition sources, in a well-ventilated spot. Quantity limits for storage are set by your local fire code and your insurer, and they depend on what the lot's safety data sheet says. We can tell you what documents are available for a lot if you ask in writing through the wholesale page before ordering, and a local fire marshal or an environmental health and safety professional is the right person for building rules.
For the retail-bottle version of all this, see how to store fir needle oil, and if you buy for a studio, the batch consistency routine pairs well with a decanting schedule.
Keep the big one full and shut, and the last pound will smell like the first.
Fir Needle Essential Oil
Fir Needle Essential Oil from our own shop, in sizes from 0.5 oz to bulk.
From $10.99
Shop Now →