Storing rosin, wax and crumble: cold, silicone, three mistakes

The reference ranking dates from 1976 and still holds. Published in the Journal of Pharmacy and Pharmacology, that work covered herbaceous samples, resins and solutions of pure cannabinoids followed for up to two years. Exposure to light, even out of direct sun, comes out as the leading loss factor, particularly in solution. The effect of temperature up to 20 °C was judged of little significance, while oxidation in air brought clear losses. A decisive detail for reading an old certificate: the loss caused by light does not raise cannabinol, whereas oxidation in air in the dark does.

A study published in 2020 in Frontiers in Plant Science took the question up again over twelve months, in the dark, at four temperatures ranging from minus 80 °C to 25 °C, on inflorescences and on extracts. Two figures are enough to frame the subject: mean terpenoid concentration fell by more than 50% as early as four months, whatever the temperature, while total phytocannabinoids lost an average of only 26% over twelve months. Degradation products, CBN included, rose most at 25 °C.

The same work delivers the result most transposable to concentrates: ground samples oxidised more than whole buds, because they expose more surface to the air. A slab of rosin spread into a thin sheet, or a crumbled crumble, present exactly that flaw. A compact block ages better than the same mass scattered about.

That leaves moisture. For dried flower, standard ASTM D8197-22 sets a water activity between 0.55 and 0.65, the upper bound to rule out the development of micro-organisms, the lower one to avoid breakage. No equivalent public standard exists for concentrates: on that point, caution stands in for a rule, and the water brought in by condensation remains the main risk.

Three containers circulate in this family of products, and they do not play the same role.

Glass is chemically inert and closes airtight. It is the default storage container, provided it is opaque or kept in the dark, since light is the leading loss factor. A jar sized to the quantity also cuts the volume of air trapped in with the product.

Silicone is chosen for its non-stick surface, the only convenient answer to a sticky texture such as a wax or a fresh rosin. It is a container for handling and transport. No published comparison allows anyone to state that it matches glass over long storage, and we do not state it: in practice, silicone to handle, glass to keep.

Silicone-coated paper is for folding and transfer. It forms no barrier against air and is not a storage container.

Flexible plastic, for its part, poses a measured problem. d-limonene, a monoterpene abundant in hemp, is a solvent for polystyrene: an article published in 2013 in Advanced Materials describes the dissolution of polystyrene by that compound at room temperature, its dielectric constant being close to that of toluene. A foam tray, a soft styrene-based pot or a thin plastic bag are therefore ruled out from the start for a terpene-rich product. Our guides to wax and concentrates and to solvent-free rosin describe where those textures come from.

Cold slows things down, it does not freeze them in place. In the 2020 study cited above, the best measured condition for preserving the original composition was storage at 4 °C, whole inflorescences, and the same 4 °C for extracts subsequently kept in oil. At 25 °C, degradation products rose the most. The refrigerator therefore has real value over long durations.

The freezer, on the other hand, is not the improved version of the refrigerator. In that same study, very low temperatures were among the least favourable to terpenoids, and grinding made the phenomenon worse still. Going colder than necessary costs scent and gains nothing elsewhere.

The real trap with cold is physical, not chemical. When a surface is colder than the dew point of the air around it, water vapour condenses on it: the same mechanism as mist on a window pane or morning dew. A jar taken out of the refrigerator and opened straight away in a warm room therefore receives liquid water onto its contents, and that water does not leave again. The rule fits in one sentence: the container comes back to room temperature closed, and is opened only afterwards.

Over a short duration, a few weeks to a few months, cold is not even essential. The 1976 work judged the effect of temperature of little significance up to 20 °C and reckoned that a well-prepared resin or extract stays reasonably stable for one to two years in the dark, at room temperature. A dark, cool drawer beats a badly used refrigerator. The same reasoning holds for flower, set out in our guide on storing flowers.

Opening the jar straight out of the cold. This is the most frequent and the most costly mistake, because it introduces liquid water into a product that holds none. Take the container out closed, wait until it has come back to room temperature, then open it. Multiplying round trips between cold and warm multiplies the condensation episodes: better to take out a portion and leave the rest alone.

Using a flexible plastic or a foam. Polystyrene dissolves in d-limonene at room temperature. A thin bag or a foam tray damage the product and mark themselves in the process. Glass to keep, silicone to handle.

Touching the product with your fingers. The hand warms it, brings moisture and residues, and holds back part of the material. A clean, dry tool, in metal or glass, settles the matter. On the same logic, a concentrate is not crumbled in advance: surface exposed to air is exactly what the 2020 study identified as an aggravating factor.

Let us say it plainly: the Phytogrammes catalogue holds neither wax nor crumble. It holds flowers, oils and resins obtained by mechanical separation, without solvent, from dry sift to full melt. This article is therefore an informational one, not a sales page, and it recommends no oral use: these products are not foodstuffs and are restricted to adults.

The legal framework stays the same whatever the process. The arrêté du 30 décembre 2021 (the French ministerial order on hemp) authorises only Cannabis sativa L. varieties listed in the official catalogues, whose delta-9-THC content does not exceed 0.30%, and applies the same threshold to extracts and to the products containing them. That threshold is checked on the batch certificate, drawn up by a third-party laboratory accredited to ISO/IEC 17025, never on the texture or the colour. Questions about orders and tracking are gathered on the FAQ page.

• Fairbairn, Liebmann and Rowan, Journal of Pharmacy and Pharmacology, 1976
• Milay et al., Frontiers in Plant Science, 2020 (post-harvest storage)
• Kwaśnica et al., Foods, 2020 (volatile composition of hemp flowers)
• Hearon et al., Advanced Materials, 2013 (dissolution of polystyrene by d-limonene)
• ASTM D8197-22, water activity of dried flower
• Dew point, definition and condensation on a cold surface
• Légifrance, arrêté du 30 décembre 2021 (the 0.30% threshold)
• ISO/IEC 17025, testing and calibration laboratories
• Phytogrammes, CBD wax and concentrates
• Phytogrammes, rosin and solvent-free extraction