What are micron sieves used for in dry extraction?
In traditional extraction methods (such as dry sift), several successive sieves are used—each with a different mesh size—to filter trichomes according to their size. Trichomes vary between 20 and 120 microns depending on their maturity, type, and plant variety.
Sieve size: 25–45 µm | What is filtered: Broken buds, small debris, contaminants | Expected result: Fine but less rich
Sieve size: 70–90 µm | What is filtered: Whole glandular trichomes (optimum) | Expected result: Very pure and concentrated resin
Sieve size: 100–160 µm | What is filtered: Plant fragments + trichomes | Expected result: Less concentrated, greener
Why does the 90 µm sieve produce resin that is too rich in THC?
In a legal CBD context, resin must contain less than 0.3% (EU) or 1% (Switzerland) THC. However, the 90 µm sieve is precisely the one that retains the majority of mature trichomes, which contain the highest levels of cannabinoids... so THC is also highly concentrated in them.
By sieving only at 90 µm:
- The entire trichomes, rich in THC and CBD, are isolated.
- You obtain an ultra-pure, very beautiful resin, but one that does not comply with the law
- The THC/CBD ratio becomes disproportionate for a so-called CBD variety
Legal resin: a balance to be respected
To produce legal resin in Europe or Switzerland, you must:
- Mix several sieving fractions (e.g. 45–160 µm)
- Add pollen with a lower THC content
- Reintroduce plant material low in cannabinoids
- Avoid selections that are too fine or too pure
In summary
- 90 µm | Explanation: Too rich → risk of exceeding legal THC limits
- 25 µm | Explanation: Too low → Mainly debris and contaminants
- Legal CBD resin | Explanation: Requires a mixture of sizes ranging from 75 to 150 microns + rigorous control
- Artisanal appearance | Explanation: Yes, but under constant analytical control
Goldbar420 advice
At Goldbar420, our resins are produced using traditional Rif craftsmanship, but comply with legal standards thanks to:
- Control of sieve sizes
- A Swiss control laboratory
- Full traceability, from field to bag
We choose fractions between 75 and 160 microns to preserve the taste, texture and potency, without ever exceeding the legal THC threshold.
