Heat, pressure, and nothing added
Two heated plates and a force. The material is placed between them, squeezed until the resin flows out, and collected. Nothing is added at any point and nothing has to be removed afterwards.
That is the entire process, and its appeal is precisely that brevity. It sits between mechanical separation, which detaches glands without opening them, and solvent extraction, which dissolves their contents.
This page covers what physically happens under the plates, what temperature and pressure each control, what determines the yield, how the input material changes the result, and what a certificate should and should not show.
⚠️ Scope. This page describes a process and what can be verified from documents. It does not describe what a product does to a person, gives no amounts, and does not replace a healthcare professional.
🔴 What happens under the plates
The glands rupture
Pressure bursts the cuticle membrane holding the contents. The gland heads open rather than merely detaching.
The contents liquefies
Heat lowers the viscosity of what was inside. At room temperature the material would not flow; warmed, it does.
It flows outward
The combination of pressure and reduced viscosity drives the liquid out of the material and onto the collection surface.
What stays behind
Plant matter, cell walls, and whatever did not flow. It remains as a compressed pad between the plates.
The two variables
Temperature
It controls viscosity. Warmer material flows more readily and gives up more of its contents; it also loses more volatile compounds.
Pressure
It controls the driving force. More pressure moves more material; beyond a point it also drives plant matter through with it.
How they trade
Lower temperature with higher pressure and longer duration gives a cleaner result at lower yield. Higher temperature gives more, faster, and coarser.
Where operators sit
Across the whole range, deliberately. Different products are targeted by different settings and both ends of the range are legitimate.
What temperature specifically costs
The volatile compounds
They begin leaving well below the temperatures used. Every degree above the minimum viable point removes more of the aromatic profile.
The colour
Warmer pressing gives a darker result. It is a reliable visual indicator of how the material was worked.
The texture
Temperature affects how the collected material behaves afterwards, and it is one of several inputs into the final consistency.
What it does not change
The compliance calculation. Total THC, as delta-9-THC plus THCA multiplied by 0.877, concerns the composition rather than the process.
What pressure specifically costs
Plant matter carryover
Beyond a threshold, pressure drives cell contents and fragments out along with the resin. The result becomes greener and less clean.
The bag question
Material is usually pressed inside a fine mesh bag, which retains plant matter. The bag mesh is therefore a variable in its own right.
Mesh selection
Finer mesh gives a cleaner result and lower yield, because it retains more. Coarser mesh passes more of everything.
The compromise
Most operators use a mesh matched to the input: finer for flower, coarser for already-separated fractions.
🔴 What the input material changes
Flower
The most common input. Yield is modest, the result carries some plant character, and mesh selection matters most here.
Dry sieved fractions
Already separated by size, so plant matter is largely absent. Pressing yields more and cleaner from the same mass.
Water separated fractions
The highest-value input. The result is clean and the aromatic profile depends on whether the fraction came from fresh or dried material.
The general rule
Pressing does not clean. It moves what is already there, so the cleanliness of the output tracks the cleanliness of the input almost exactly.
Yield in practice
From flower
A modest fraction of the starting mass. It varies with gland density, moisture and technique more than with any equipment setting.
From separated fractions
Substantially higher, because the input is already concentrated and contains little that will not flow.
What limits it
Whatever does not liquefy at the temperature used, and whatever the mesh retains. Both are deliberate choices.
Comparison with solvent routes
Considerably lower. Solvents recover material that pressing leaves in the pad, which is the basis of their volume advantage.
Moisture and its effect
Too dry
The material does not compress well and the resin does not carry out cleanly. Yield falls.
Too damp
Water is expressed along with the resin, and the result carries it. It affects texture and it creates a storage problem.
The working range
Roughly the same range that suits storage. Material held in that band presses better than material at either extreme.
What this connects to
Storage humidity, directly. Material that was kept properly presses better, which is a practical consequence of a storage decision.
The collection surface
What is used
Parchment or a similar non-stick sheet. The resin flows onto it and is collected once cool.
Why the choice matters
An unsuitable surface holds the material and makes recovery incomplete. It is a small variable with a measurable effect on yield.
Temperature at collection
Warm material is easier to move and loses more volatile compounds while it is warm. Cooling before handling preserves more.
The handling afterwards
Every manipulation while warm costs aroma. Working cold is slower and preserves more.
What comes out
The forms
The material sets into various consistencies depending on temperature, input and subsequent handling. It is one substance in different physical states.
Why the state varies
Temperature history, agitation, and the proportion of different compounds. Small differences produce visibly different results.
Whether state indicates quality
Not directly. Consistency is a physical property influenced by many variables and it does not track purity or content.
What does indicate quality
Colour, absence of plant matter, and the certificate. In that order of increasing reliability.
Colour and what it means
The pale end
Cooler pressing, cleaner input, and less oxidation. It is generally the more valued appearance.
The darker end
Warmer pressing, more plant carryover, or age. Three causes with a similar visual result.
The green tint
Chlorophyll, meaning plant material came through with the resin. It is the clearest indicator of a mesh or pressure choice.
What colour cannot tell you
Content. A pale press and a darker one from the same input can measure comparably.
The residual solvent question
Whether it applies
No. Nothing is added, so nothing can remain. This is the process’s principal claim and it is accurate.
What that means for a certificate
The absence of a residual solvent panel is reasonable on a genuinely pressed product.
The claim that follows
Solvent-free is precise here rather than approximate. It is one of the few places in this category where the phrase means exactly what it says.
What it does not cover
Everything else. Pesticides, heavy metals and microbiology apply regardless of extraction method.
Contaminants and the concentration factor
What concentration does
It multiplies everything present in the input, including what should not be there.
Why this matters here specifically
Because the process is often presented as clean by virtue of using no solvent, which addresses only one of several contaminant categories.
What the certificate should cover
Pesticides, heavy metals and microbiology on the finished product. The concentration factor makes them more consequential than on the input.
The common gap
Producers testing the input material and not the output. The two are different products with different figures.
Equipment and scale
Small presses
Hand-operated or hydraulic, working a few grams at a time. Accessible in cost and slow in throughput.
Larger presses
Hydraulic or pneumatic, with heated platens and controlled temperature. Throughput rises and the physics does not change.
What scale changes
Consistency, principally. A controlled press delivers the same temperature and force every time, which hand-operated equipment cannot.
What it does not change
Yield per unit of input, which is set by the material and the settings rather than by the size of the machine.
Temperature control in practice
Why it is difficult
Platen temperature and material temperature differ. Thin material equilibrates quickly and thicker loads do not.
What operators do
Preheat briefly before applying full pressure, so the material reaches temperature before it is squeezed.
The measurement problem
Platen thermometers read the plate. What matters is the material, and nothing convenient measures it directly.
The consequence
Stated temperatures are platen temperatures. Two operators quoting the same figure may be working the material at different actual temperatures.
Pressing already-pressed material
Whether it is done
Yes. The pad retains material that did not flow the first time, and repressing at higher temperature recovers some of it.
What the second yield is like
Darker, less aromatic, and lower in quality. It is a different product from the first pass.
Whether it is disclosed
Rarely. There is no marking that distinguishes a first press from a second, and no document records which it was.
What a buyer might notice
A darker colour and a thinner aroma than the price suggests. It is an inference rather than a determination.
Storage of the result
Why it matters
The material has an exposed surface and continues to change. Oxidation proceeds faster than on intact flower.
The container
Airtight, opaque, cold, minimal headspace. The same principles applied more strictly.
The temperature question
Cold storage slows change and makes the material harder to handle. Most operators accept the inconvenience.
What changes over time
Colour darkens, texture shifts, and aroma thins. All three are visible within months.
What the process cannot do
Improve the input
It moves material rather than refining it. Poor input gives poor output at any setting.
Remove contaminants
Nothing about heat and pressure separates a contaminant from resin. Both flow together.
Recover everything
A substantial fraction stays in the pad. That is the yield limitation and it is inherent.
Substitute for testing
The absence of solvent addresses one contaminant category. The others require the same panels as anywhere.
Comparing with other routes
Against mechanical separation
Pressing opens the glands; separation collects them intact. Different products from the same starting material.
Against solvent extraction
Pressing recovers less and introduces nothing. Solvents recover more and create a residual question.
Against distillation
Distillation isolates specific fractions at high purity and removes the aromatic profile entirely. Pressing preserves what it does not destroy with heat.
Why all coexist
Different objectives: simplicity, purity of process, yield, and isolation. No single method serves all four.
The economics
Equipment cost
Modest compared with solvent extraction. A functional press costs a fraction of an extraction system.
Labour
Substantial per unit at small scale. Loading, pressing, collecting and cleaning are all hands-on.
Yield
Low relative to solvent routes, which is the principal cost driver on the input side.
Where it lands commercially
A premium product accessible to small producers. That combination is unusual and it explains the category’s position.
Where the technique came from
The recent origin
Unlike sieving, which is centuries old, pressing in this form emerged in the twenty-tens. It spread through amateur experimentation before commercial equipment existed.
The improvised beginnings
The earliest documented attempts used hair straighteners and hand pressure, which established the principle before anyone built a machine for it.
The commercial response
Purpose-built presses followed quickly, with controlled platen temperature and calibrated force. The equipment market developed within a few years.
Why it spread so fast
Because it required no chemistry, no ventilation, no solvent handling and no regulatory complexity. The barrier to entry was a press and some parchment.
The relationship to yield expectations
What is realistic from flower
A modest single-digit percentage of the input mass, varying widely. Claims substantially above that range warrant scepticism.
What is realistic from separated fractions
Considerably higher, because the input is already concentrated and contains little that will not flow.
Why the figures circulate confusingly
Because yields from different inputs are quoted without stating the input. A percentage from a water separated fraction and one from flower are not comparable.
What a buyer should take from it
Nothing directly, since yield is a producer’s concern. It matters here only because it explains the price of the output.
Multiple presses of the same load
The first press
Gives the cleanest and most aromatic material, at the lowest temperature that will make it flow.
Raising the temperature afterwards
Recovers additional material from the same pad, darker and thinner in aroma. It is a different product from the same input.
Whether the two are combined
Frequently, because separating them adds handling and the second yield still has value. Combining lowers the quality of the first.
What nothing records
Whether a given product is a first press or a blend. No document distinguishes them and no marking exists.
The bag material question
What the bags are made of
Synthetic mesh, in food-grade specifications, available in a range of openings measured in micrometres.
Why the material matters
The bag is in direct contact with heated material under pressure. Its composition and thermal stability are therefore relevant.
What careful operations use
Bags specified for the temperature range in use, from suppliers who state the material. It is a straightforward thing to verify and it is often not asked about.
The question worth putting
What the press bags are made of and to what temperature they are rated. A producer knows; a reseller usually does not.
Filtration after pressing
Whether it is done
Sometimes. Warm material can be passed through fine mesh to remove residual particulates.
What it achieves
A visibly cleaner result, particularly where the initial pressing carried plant matter through.
What it costs
Handling while warm, which loses volatile compounds. It is a trade between appearance and aroma.
How to tell
An unusually clean appearance combined with a thin aroma suggests post-processing. It is an inference rather than a determination.
The comparison that matters commercially
Against water separation
Pressing opens the glands and water separation collects them intact. The former gives a liquid product, the latter a granular one.
The input relationship
Water separated material is a premium input for pressing. The two processes are sequential rather than alternative.
The price positions
Both occupy the higher end. The combination of the two occupies the highest, because the input cost is already substantial.
What a buyer is choosing between
Not really methods but products. A pressed product and a separated fraction are different things, and the choice is about which is wanted.
What the certificate looks like
The content figures
Substantially higher than the input material. The concentration factor is the expected part.
The compliance calculation
Total THC applies to the finished product. Concentration raises it proportionally, which constrains what can be made from compliant input.
The panels that matter
Pesticides, heavy metals and microbiology. Concentration makes each more consequential.
The panel that does not
Residual solvents. Its absence here is correct rather than a gap.
Reading a listing
What should be stated
The input material, the general pressing approach, and a link to the batch certificate. Three items.
What usually is stated
A name, an appearance description, and a price. The three that matter are frequently absent.
The question that fills the gap
What was pressed. Flower, dry sieved or water separated. The answer changes what the product is.
What a specific answer indicates
Someone connected to the production. A vague one indicates a reseller, which is not disqualifying and is worth knowing.
The temperature debate
The low-temperature position
Preserve aroma at the cost of yield, on the argument that the aromatic profile is what distinguishes the product.
The higher-temperature position
Accept aroma loss for materially better yield, on the argument that the economics otherwise do not work at small scale.
What both agree on
That there is a trade, that it is direct, and that where to sit on it is a commercial decision rather than a technical one.
What a buyer sees of it
Colour and aroma, which together indicate roughly where the producer sat. It is the most legible process choice in this category.
What this process demonstrates generally
The separation of claims
Solvent-free is established by the method. Clean is not, and the two are routinely presented together.
Why that distinction is worth holding
Because it recurs across every process in this category. What a method establishes and what it is marketed as establishing are frequently different.
The check that follows
Look at what the certificate covers rather than at what the process description implies. The panels are the answer.
The general principle
A process claim addresses the process. Product claims require product measurements, and the two are not interchangeable.
What the pad is worth afterwards
What remains in it
Plant material with whatever did not flow at the temperature used. On a first press at low temperature that can be a substantial fraction of the original content.
Where it goes
To solvent extraction, generally, where the remaining material can be recovered by a method that does not depend on flow. Nothing is wasted in a well-run operation.
Why this matters to the economics
The low yield of a cool first press is less costly than it appears, because the pad retains value. The two processes complement each other rather than competing.
A short glossary
Platen
The heated plate of a press. Its stated temperature is what is controlled, and the material temperature follows it imperfectly.
Press bag
Fine mesh enclosing the material during pressing, retaining plant matter while allowing resin through.
First press
The initial extraction from fresh input. Subsequent presses of the same pad give lower-quality material.
Carryover
Plant matter driven through the mesh along with the resin, generally under excessive pressure.
Non-stick sheet
The collection surface onto which the resin flows, from which it is recovered once cooled.
The five checks that apply to any product
The batch certificate
Request it with the number printed on the packaging. A general document for the product line does not cover this batch, and those differences are exactly what it should record.
Total THC
Delta-9-THC plus THCA multiplied by 0.877, because THCA becomes THC under heat and the limit applies to the sum, not to either value alone.
Price per milligram
A division, not an opinion. The only figure that makes two products comparable, whatever the format, process and pack size.
The claims
Without an authorisation number in the EU Register these are assertions, not data — and for cannabidiol that register contains no authorised entry to this day.
The seller’s details
Company name, address and contact. Without them there is also no counterparty to turn to if something turns out to be wrong.
How this connects to the rest
With mechanical separation
Separated fractions are the highest-value input here. The two processes are complementary rather than competing.
With storage humidity
Material held in the correct range presses better than material at either extreme.
With residual solvents
This is the one process where the absence of that panel is genuinely reasonable rather than a gap.
With contaminant testing
Concentration makes those panels matter more, and the solvent-free claim addresses none of them.
What this is for in practice
When buying
Ask what the input was. Flower, dry sieved or water separated are three different products under one process name.
When judging colour
Pale generally indicates cooler pressing and cleaner input. A green tint indicates plant carryover.
When reading a certificate
Expect no residual solvent panel and require the contaminant panels. That is the correct expectation here.
When storing
Airtight, opaque, cold, small headspace. More strictly than for flower.
Frequently asked questions
Is any solvent used? No. The process is heat and pressure only, so nothing is added and nothing can remain.
What do the two variables control? Temperature controls viscosity and therefore flow. Pressure controls the driving force and the amount of plant matter carried through.
Does higher temperature give more? Yes, and it removes more of the aromatic profile and darkens the result. It is a direct trade.
What input gives the best result? Water separated fractions, generally. The process does not clean, so output cleanliness tracks input cleanliness.
Why does the mesh matter? It retains plant matter. Finer mesh gives a cleaner result at lower yield; coarser mesh passes more of everything.
Does the process remove contaminants? No. Heat and pressure do not separate a contaminant from resin. Both flow together.
Should there be a residual solvent panel? Not on a genuinely pressed product. Its absence here is reasonable rather than a gap.
What does colour indicate? Cooler pressing and cleaner input at the pale end; warmer pressing, plant carryover or age at the darker end.
Is the pad pressed again? Sometimes. The second yield is darker and less aromatic, and nothing on a package distinguishes it.
How should it be stored? Airtight, opaque, cold, with minimal headspace. It oxidises faster than intact flower.
What we check and what we do not
We check what can be checked from documents: official registers, declared contents, certificates of analysis, arithmetic. We test no products, rank nothing, and assert no effects.
This process has an unusually clean claim behind it: nothing is added, so nothing can remain. That statement is exactly true, and it is worth noting how rare exact statements are in this category.
It is also frequently stretched into something broader. A process that introduces no solvent still concentrates whatever the input carried, and the contaminant panels on the certificate matter more here rather than less. Solvent-free and clean are two different claims, and only the first is established by the method.