Rosin is cannabis resin pressed out with heat and pressure only, with no solvent. This part covers what goes into the press, which filter bag to use, what yields are realistic, how rosin is cured and stored, the injuries presses cause, and how to read common faults.
The legal position has not changed from Part 1. In Thailand, an extract above 0.2 percent THC by weight is a Category 5 narcotic. A licence under the Ministerial Regulation on Cannabis or Hemp Extracts B.E. 2569 (in force 26 April 2026) goes only to Thai juristic persons that are not “foreign” under the Foreign Business Act B.E. 2542, state agencies and the Thai Red Cross Society. Pressing rosin outside that framework is a narcotics offence. This guide is technical education for licensed operators and for readers where processing is lawful.
This is Part 2. Part 1: Rosin: Solventless Extraction with Heat and Pressure
7. Starting Material
The press cannot add anything the input does not already have. Good rosin starts with good, clean, resin-rich material.
Moisture and Equilibration
Equilibration means storing material in a closed space until its moisture matches the air around it. Practitioners say flower equilibrated to about 55 to 62 percent relative humidity presses best. No traceable published measurement stands behind this figure.
Too dry, and the material acts like a sponge: it soaks up oil instead of releasing it. Too wet, and steam drives water through the bag with the resin. The result is cloudy oil that separates.
Translator’s note: In the Thai rainy season the outside air is often above 80 percent humidity. Material left open will take on water and drift above the target. Keep material sealed in airtight jars, ideally with two-way humidity packs rated near the target (Curing Cannabis in Jars explains these packs). Check the jar with a calibrated hygrometer before pressing, and open it in an air-conditioned room. A power cut switches the air conditioner off and room humidity rises fast, so keep jars closed until the room is back under control.
Cured Flower, Dry Sift and Ice Water Hash
Cured flower is the whole product. The resin is still attached to plant tissue.
Dry sift, also called kief, is trichome material shaken through screens from dried plant matter (see Dry Ice, Dry Sift and Charas). Reference material notes that pure kief turns soft and sticky when heated, which is why it presses easily.
Ice water hash is made by stirring material in iced water until the trichomes sink and the lighter plant matter floats. The separated resin turns hard and brittle. How the wash is done (micron bags, fresh frozen input, freeze drying and grading) is covered in Ice Water Extraction and Bubble Hash.
Why Hash Rosin Yields So Much More Than Flower Rosin
With flower, heat and force must tear resin off plant material and filter it in one step. With hash, the separation already happened in cold water, without heat damage.
The yield gap is also large because the starting weight is different. Hash yield is measured against hash, which is mostly resin. Flower yield is measured against stems, fibre and cell walls as well. Reference material notes that the highest grades of hash, called full melt because they melt completely when heated, need no pressing at all.
What to do: if you are licensed and want the cleanest rosin, separate the resin first by dry sifting or washing, then press the hash. Record which input you used every time.
8. Choosing the Filter Bag Mesh
Filter bags are graded in microns (1 micron = 1/1,000 of a millimetre), the size of the holes in the mesh. Coarse mesh lets oil flow freely but also lets plant particles through. Fine mesh filters hard but resists flow, which raises the risk of a blowout (the bag bursting under pressure).
Published reference material gives two fixed points. In ice water hash, the resin heads collect mostly in the 73 and 90 micron grades. Full spectrum hash rosin, pressed from hash collected across several grades, is generally made from 45 to 159 micron material.
The pairings below are unsourced practice.
| Input | Reported bag mesh | Reason |
|---|---|---|
| Whole cured flower | 90 to 160 micron | Coarse mesh lets oil flow through bulky plant material |
| Ground flower | 90 to 120 micron | Smaller particles need tighter filtering |
| Dry sift or kief | 25 to 90 micron | Already cleaned; fine mesh catches fragments |
| Ice water hash, full melt | 25 to 45 micron | Almost pure resin; the bag mainly holds the melt in place |
What to do: start with the mesh in the table for your input. If you get blowouts, check fill level and force ramp-up before switching to a coarser bag.
9. Realistic Yields by Input
Published reference material gives hash rosin yields of 0.3 to 8 percent. Yields reported by practitioners are far higher. The table keeps both so you can see the gap.
| Input | Reported yield | Where the figure comes from |
|---|---|---|
| Cured flower, average quality | 12 to 18 percent by weight | Practitioner reports, unsourced |
| Cured flower, high resin | 18 to 25 percent by weight | Practitioner reports, unsourced |
| Dry sift or kief | 30 to 55 percent by weight | Practitioner reports, unsourced |
| Ice water hash, full melt | 60 to 80 percent by weight | Practitioner reports, unsourced |
| Hash rosin, published range | 0.3 to 8 percent | Published reference material |
| Hydrocarbon extraction | 10 to 20 percent | Published reference material |
The published 0.3 to 8 percent range refers to hash rosin and is even lower than hydrocarbon’s 10 to 20 percent, but the source does not say what weight it is calculated on. Until that is clear, do not mix the two sets of numbers.
Hash yields are calculated on the weight of the hash, not the flower the hash came from. So “60 percent” from hash is not 60 percent of your flower. Seller figures also run high because they quote best cases. Treat every yield claim as an upper limit, not an expected result.
What to do: weigh your input and your collected rosin on the same scale, and always state what the percentage is calculated on (flower, sift or hash).
10. After the Press: Curing, Textures and Storage
Fresh rosin is not finished. Its texture depends on the hours and days after it leaves the plates. Everything in this section is practitioner practice; no published measurement stands behind the temperatures.
Cold Cure, Hot Cure and “Jar Tech”
Cold cure means sealing the collected oil in a jar at about 4 to 15 °C for a day to several weeks. The rosin firms up and turns lighter, opaque and spreadable. Most pressers prefer it, because nothing aromatic is driven off.
Hot cure means holding sealed rosin at about 35 to 55 °C. It forces the same change in hours, but costs aroma. “Jar tech” is the general name for these sealed cures.
Translator’s note: A Thai room at 30–35 °C is just below the hot-cure range. Rosin left on a shelf will drift toward hot-cure results and lose aroma. A cold cure needs a refrigerator. Put a thermometer inside, keep the jar sealed, and open the fridge as little as possible; during a power cut, keep the door shut.
Budder, Badder and Shatter-Like Rosin
These names describe physical states, not different chemistry. Budder and badder are opaque, whipped or self-buttering textures. They form when the oil nucleates, meaning many tiny crystals start forming throughout it. Cold curing usually drives this.
Shatter-like rosin is glassy and see-through. It forms when the oil stays uniform, usually from very clean, low-moisture input handled gently.
Breakdown and Storage
Rosin breaks down through heat, light, oxygen and time. The decarboxylation study cited in Part 1 shows the direction: above 100 °C, breakdown of neutral cannabinoids such as THC dominates. Cannabinol (CBN) builds up, but it does not account for all the loss.
What to do: store rosin cold, dark and airtight. Use a jar small enough to leave little air above the rosin, and reheat it as little as possible.
11. Equipment, and the Hazards That Actually Injure People
A hair straightener applies heat and some force, and it will produce rosin. It is a poor tool for four mechanical reasons:
- Its plates are narrow, curved and built to grip hair, not to stay parallel.
- The force comes from your hand, so it can be neither measured nor repeated.
- Its thermostat is made for hair and runs far hotter than any rosin band.
- The plates flex under load.
A purpose-built press gives flat, parallel plates, even heat, and a force you can read and repeat.
Flat Plates and Even Heat
Pressure follows contact. A plate that bends slightly under load puts most of its force on a small area. Part of the puck is over-pressed while the rest is barely touched. The result is uneven flow and a scorched patch.
Thin plates with one heating element in the centre run hot in the middle and cold at the edges. The real press temperature then depends on where the bag sits.
What to do: place the bag in the same spot on the plates every time, and check plate flatness if one side of your pucks keeps scorching.
The Real Hazards
Crushing is the most serious injury. A press closes with thousands of pounds of force (well over a tonne) and does not stop for what is between the plates. Fingers do not survive. Keep your hands out of the plate path, and never adjust a bag while the press is under load.
Burns come from surfaces that look the same hot or cold. Metal tools left on the plates carry heat straight into your hand.
Hydraulic failure is the reason to wear eye protection. A failed seal, hose or fitting can release oil as a high-pressure jet. Pneumatic (air-driven) systems fail even faster.
What to do: wear eye protection whenever the press is under load, and inspect hoses and fittings at the start of every session.
Translator’s note: If the power fails during a press, the heater stops but a hydraulic press can stay under load. Release the pressure with the valve first, then remove the bag. Do not reach between the plates while they are still closed.
12. Quality Checks and Common Faults
Extraction concentrates whatever is on and in the plant. A clean method does not make dirty input clean.
A 2020 review by Montoya and colleagues in the journal Frontiers in Pharmacology shows how large the problem is. An analysis in Washington State (USA) found that 84 percent of cannabis samples contained up to 24 different insecticides, miticides, fungicides, synergists (chemicals added to make a pesticide stronger) and plant growth regulators (see Plant Growth Regulators). Dispensary testing in California (USA) found that 49 percent of samples contained pesticides meant only for ornamental plants, including abamectin and bifenazate.
The review warns that lipophilic pesticides (ones that dissolve in fats and oils) dissolve into extraction solvents. That warning targets solvent methods, and rosin avoids that route. But heat and pressure do not remove pesticide residue or metals from resin either. “Solventless” means no solvent was added; it does not mean the product is clean.
Translator’s note: In Thailand, use only pesticides registered with the Department of Agriculture (กรมวิชาการเกษตร), and only as the label says. Check the registration and the label before using any product, including abamectin or bifenazate products. Have both the input and the rosin tested by a laboratory; Pesticide Residues on Cannabis and What You May Legally Spray on Cannabis Under Thai GACP explain how.
| Fault | Common causes | What to do |
|---|---|---|
| Dark or amber-brown oil | Temperature too high; press too long; degraded input | Lower temperature, shorten press time, check the input |
| Green tint | Chlorophyll pulled through; too much force; mesh too coarse | Reduce force, use finer mesh, pre-press the puck |
| Blowout (bag bursts) | Force applied too fast; bag overfilled; mesh too fine | Raise force gradually, fill loosely, match mesh to input |
| Cloudy or separating oil | Too much moisture pushed through as steam | Equilibrate the material to a lower humidity first |
| Very low yield | Input too dry; temperature too low; force too low | Rehydrate the material, or recalculate pressure from bag area |
| Gritty texture or particles | Filter failure, torn bag, contamination | Inspect the bag; discard the run |
Reference material on hashish adds that leaf contamination typically gives a greenish product. That is exactly what chlorophyll pull-through looks like in a rosin puddle.
Colour alone is a weak test of quality. Light-coloured rosin from a poor cultivar is still poor rosin.
What to do: grade rosin on aroma, texture and lab results, not on colour alone. When a press fails, find the cause in the table above before changing settings.
13. Where Practical Experience Ends
Most numbers in solventless work are practical experience that has never been formally measured. This includes the temperature bands, press times, humidity targets and mesh pairings. That does not make them worthless, but they should be labelled as experience, not fact.
If you press where it is lawful, post your real numbers below this topic, not your best ones. Include input type, equilibration humidity, plate temperature, bag size and force applied, with pressure calculated from bag area rather than read off the gauge. Report what failed as well as what worked, including blowouts and green presses. Numbers from different growers only become comparable when everyone reports bag size alongside settings.
This article is part of the Asiannabis Community educational series on extraction and post-harvest processing. It is for education in places where cannabis processing is legally permitted.
References
- Nishimura & Asahi: legal analysis of the February 2022 Ministry of Public Health notification listing Category 5 narcotics (as cited in the original article).
- Tilleke & Gibbins: analysis of the Notification of the Ministry of Public Health Re: Controlled Herbs (Cannabis), B.E. 2568 (as cited in the original article).
- Ministerial Regulation on Cannabis or Hemp Extracts B.E. 2569 (2026).
- Moreno T, Dyer P, Tallon S. Cannabinoid Decarboxylation: A Comparative Kinetic Study. Industrial & Engineering Chemistry Research, 2020, 59(46): 20307–20315. doi:10.1021/acs.iecr.0c03791
- Montoya Z, Conroy M, Vanden Heuvel BD, Pauli CS, Park SH. Cannabis Contaminants Limit Pharmacological Use of Cannabidiol. Frontiers in Pharmacology, 2020, 11. doi:10.3389/fphar.2020.571832
- General reference material on hash oil and hashish (not named in the original article).