Storing rosin, wax and crumble: 4 °C, glass and 3 mistakes
Four things degrade a hemp concentrate: light, oxygen, heat and water. Terpenes are lost long before cannabinoids; in one storage study, more than half were gone in four months, even in the dark. Keep it in a well-closed glass jar, cool and dark, and open it only once it is back at room temperature. Phytogrammes sells neither wax nor crumble, and this article is for information only.
Key takeaways
- Terpenoid losses passed 50% in four months in a 2020 study, while cannabinoids lost 26% in twelve months.
- Most losses come from light, and air raises CBN even in the dark.
- The best storage temperature measured was 4 °C; terpenoids keep less well below −20 °C.
- Foam and thin plastic pots are ruled out because d-limonene, an abundant hemp terpene, dissolves polystyrene.
- Open a jar from the fridge only after it has warmed to room temperature, or moisture from the air will settle on the product.
The four factors that degrade a concentrate
The standard ranking goes back to 1976. Fairbairn, Liebmann and Rowan tracked solutions of pure cannabinoids, nine herbal samples and two resin samples for up to two years. Light caused the most loss, particularly in solution. Temperature had little effect up to 20 °C, while oxidation by air caused clear losses even in the dark.
One detail is useful when you read an old analysis. Losses caused by light did not raise cannabinol (CBN); air oxidation in the dark did. A high CBN level therefore suggests a product left exposed to air for a long time. This molecule is described in our comparison of CBD and CBN.
A study published in 2020 in Frontiers in Plant Science took up the question again, storing inflorescences and extracts in the dark for twelve months at 25 °C, 4 °C, −30 °C and −80 °C. In every condition, mean terpenoid content dropped by more than 50% within four months. The cannabinoids produced by the plant lost only 26% on average over the twelve months, and the biggest changes occurred at 25 °C.
For concentrates, the most useful result in that work is that ground samples oxidised more than whole buds, since more of their surface is in contact with air. Rosin pressed into a thin sheet, or crumble broken into bits, has the same weakness. The same mass keeps better as one compact block than scattered.
Water is the fourth factor. For dried flower, the ASTM D8197 standard sets a water activity of 0.55 to 0.65; mould becomes a threat above that range, and the flower turns brittle below it. Concentrates have no equivalent public standard, and for them the main risk is water brought in by condensation.
The container: glass for keeping, silicone for handling
These products are usually kept in one of three containers, each suited to a different job.
| Container | Role | Long-term storage |
|---|---|---|
| Airtight glass, opaque or kept in the dark | Storage | Yes |
| Non-stick silicone | Handling, transport | No published data |
| Silicone-coated paper | Folding, transfer | No, no barrier to air |
| Foam or soft polystyrene pot | None | No, dissolved by d-limonene |
Glass is chemically inert and closes tightly. That makes it the default choice for storage, as long as it is opaque or kept in the dark, light being the main cause of loss. A jar sized to the quantity also reduces the air shut in with the product.
People choose silicone because nothing sticks to it, which helps with tacky textures such as wax or fresh rosin. No published comparison shows that it protects as well as glass over long storage, and we make no such claim. Silicone-coated paper is for folding and transferring, and air passes through it.
Thin plastic raises a documented problem. In hemp flowers analysed in 2020 in the journal Foods, d-limonene accounted for about 10% of the volatile compounds. An article published in 2013 in Advanced Materials reports that d-limonene dissolves polystyrene, its dielectric constant being close to that of toluene. Keep a terpene-rich product out of foam trays and soft styrene pots. Where these textures come from is explained in our guides to wax and concentrates and to solventless rosin.
Cold: what it really changes
Cold slows degradation down without stopping it. The 2020 study found 4 °C to be the best condition measured, both for whole inflorescences and for extracts dissolved in olive oil. Over several months of storage, a fridge does help.
Going colder brings nothing more. The authors place temperatures below −20 °C, along with grinding, among the least favourable conditions for terpenoids. A home freezer runs at about −18 °C. The study did not test that temperature, but it found no benefit in going below 4 °C.
The real risk of cold storage is physical. Water vapour in warm air condenses when it meets a cold surface; Météo-France describes this change to liquid as the temperature falls, the same process that forms dew. If you open a jar straight from the fridge in a warm room, liquid water lands on what is inside. Let the closed jar return to room temperature first, then open it.
Storage of a few weeks does not need cold at all. According to the 1976 study, well-prepared herbal cannabis, resin or extracts remain reasonably stable for one to two years in the dark at room temperature. A cool, dark drawer is better than a fridge used badly. Our guide to storing flowers applies the same reasoning to flower.
Three mistakes that cost terpenes
The most common mistake is opening the jar as soon as it leaves the cold, which puts liquid water on a product that contains none. Take the jar out closed and open it only once it has reached room temperature. Every move from cold to warm brings another round of condensation, so take out one portion and leave the rest in the cool.
The second is using thin plastic or foam. Since d-limonene dissolves polystyrene, a thin bag or a foam tray spoils the product and is marked by it in turn.
The third is handling the product with your fingers. Your hand warms it, leaves moisture and residues, and takes away some of the material, so use a clean, dry tool made of metal or glass. Do not break up a concentrate in advance either, since the 2020 study identified the surface exposed to air as an aggravating factor.
What Phytogrammes sells, and what it does not
There is no wax or crumble in the Phytogrammes catalogue. It has flowers, oils and resins made without solvent, by dry sieving such as dry sift or with ice water. The purpose of this article is to inform. It recommends no oral use, as these products are not foodstuffs and are reserved for adults.
Whatever the process, the legal framework does not change. The order of 30 December 2021 allows only Cannabis sativa L. varieties listed in the official catalogues whose Δ⁹-THC content does not exceed 0.30%, and applies that threshold to extracts and to products containing them. That threshold is read on the lot's certificate of analysis; texture and colour say nothing about it. Our laboratory page lists the catalogue products, and ordering questions are gathered in the FAQ.
Frequently asked questions
Yes, for storage over several months: the 2020 twelve-month study found its best condition at 4 °C. A cool, dark drawer is enough for a few weeks. In both cases, let the jar reach room temperature before you open it.
Going below 4 °C brought no gain in the 2020 study, which counts temperatures under −20 °C among the least favourable for terpenoids. A freezer also increases the risk of condensation when you open the jar.
Use silicone to handle a sticky texture and glass to store it. Glass is inert and closes tightly, and no published data show that a silicone pot protects as well over time.
These products are not food, so no regulatory shelf life applies. For well-prepared resin or extract kept in the dark, the 1976 study reports one to two years of reasonable stability. More than half of the terpenoids, however, disappear within four months.
Not always. A concentrate that hardens, darkens or turns grainy is oxidising and losing volatile compounds, which tells you nothing about the lot's compliance; that is read on the certificate of analysis. If it is damp or covered in fluffy filaments, though, it can no longer be used.
Written by the Phytogrammes team
Each journal article draws on cited primary sources: ANSM, EFSA, EUR-Lex and peer-reviewed publications. Product profiles are distinguished from documented laboratory results. Our approach.
Article published on . CBD is not a medicine.