Hash rosin: heat, pressure and a micron screenHash rosin: heat, pressure and a micron screen

Purpose and scope

A cannabis plant has a very large number of small glands. These glands are trichomes. Each trichome has a head on a stalk. On good flower, you can see the trichomes as white ‘crystals’.

Each trichome head is a very small bag of resin. Resin is a tacky oil that contains almost all of the potency, the aroma and the flavor of the plant. You make each solventless concentrate from these heads. You collect the heads and then press them with a small force. The method does not use chemical solvents. Examples of solvents are butane and alcohol.

The method has two parts:

1. Make the hash. Remove the trichome heads from the plant and collect them as a powder or a paste. There are two usual methods. In the first method, you mix plant material in ice water. The heads break from the plant and fall in the water (bubble hash). In the second method, you rub dried material on small screens (dry sift).
2. Press the hash into rosin. Seal the hash in a small mesh bag. Put the bag between two warm metal plates and apply force. The heat makes the resin soft. The pressure pushes the resin out through the mesh as an oil that has a gold color. This oil is rosin.

The method uses only heat plus pressure, and no solvents. Do not use too much heat or too much force. If the heat is too high, it removes the flavor. If the force is too high, it breaks the bag and pushes plant material through the mesh.

After the press, you do a cure of the rosin. In a cure, you keep the rosin at a set temperature, warm or cold. The cure sets the last texture of the rosin.

Then you can use the rosin as a dab, or put it in a vape cartridge. A dab is a small dose of rosin. You put the dose on a hot surface. The dose becomes vapor immediately, and you breathe the vapor.

In the next sections of this paper, the press has a set of controls: temperature, pressure, time and mesh size (‘micron’). The paper shows the effect of each control on the yield and the quality. It also shows the problems and how to correct them. If you do not know a term, go to the glossary at the end.

Definitions

This section gives definitions of the terms that this paper uses. Read the definitions one time. Then the next sections are easy to read.

The solventless information and the SOPs of the author give the setpoints and the micron values in this paper. They also give the method to select the press settings for each type of trichome. The author compared all of them with the sources in this paper. This paper does not replace tests of your material. Record your runs to make sure that the values are correct.

Evidence and limitations

Basic facts about the press

A rosin press has four controls: heat, pressure, time and screen (micron). All four controls change the balance of yield and quality (terpene content, color and clarity)^[1]. Heat decreases the viscosity of the resin, thus the resin flows.

Cold resin has a high viscosity and does not flow easily. When the temperature increases a small quantity, the resin flows. The resin in a trichome has the same property. But the heat that lets the oil flow also removes the lightest aroma compounds.

The micron of the bag selects the materials that flow with the oil: only trichome oil, or also lipids and plant material. Pressure and time only help the oil to flow^[2]. No control can increase the maximum quality that the steps before the press set.

The method is short. Set the quality of the input and select the product. Select a micron that agrees with the trichome heads, and set the lowest temperature that lets the oil flow. Increase the pressure only to complete the flow. Collect the rosin cold and cure it to get the texture.

Rosin production steps

Hash rosin is the last part of a longer sequence of steps. The diagram shows the steps of the cold chain in blue. In these steps, heat decreases the quality. In the press and the cure, heat is a tool.

1. 1
   Harvest

   Cut the plant at lights-off, when 80 to 90% of the trichomes are cloudy.
2. 2
   Freeze or dry

   Freeze the plant immediately for live products. Dry the plant slowly for dry sift.
3. 3
   Wash or dry sift

   Make bubble hash in ice water, or use dry sift screens. Do this work in a cold room and touch the material carefully.
4. 4
   Dry the hash

   Use a freeze dryer. You can also dry the hash in cold air. This method has a low cost.
5. 5
   Grade

   Melt a sample of the hash on a hot nail and give a grade from 1★ to 6★. The grade sets which products are possible.
6. 6
   Conditioning

   Do a check of the moisture and make the hash cold. Make a pre-press puck for flower and dry sift only.
7. 7
   Press

   Apply heat with no pressure. Increase the force slowly. Hold the force until the flow stops.
8. 8
   Collect

   Use a cold tool. Collect the rosin on new parchment and put it immediately into cold glass.
9. 9
   Select the product pathway

   The alternatives are badder, sauce, diamonds, cartridge oil and the core of a hash hole.
10. 10
    Cure

    Do a cold cure, a warm cure or a crystallization in stages.
11. 11
    Storage

    Keep the rosin in sealed glass, cold, with no light.

The next sections show each step with its values. The matrices and the problems show the control that you must change when a step has a problem.

Start setpoints for each input material

This section gives the first values for each of the four input materials. These values are start values. Change them in small steps until the result is correct. They are not targets^[7].

The temperatures are plate temperatures. Press until the oil flows. Do not press for a set time. The temperature for hash is lower than for flower, because hash contains only trichome heads, without plant material. Only sufficient heat to melt the resin is necessary^[1].

Data, conditions and unknown values

Known facts

• The terpenes and the lightness of the color stay when the plate temperature is lower. The yield and the flow are higher when the temperature is higher, but the terpenes and the lightness decrease^[1].
• A bag with a smaller micron gives rosin with less unwanted material and a higher lightness, but the yield is lower. A bag with a larger micron has the opposite effect.
• The temperature for hash and dry sift is lower than for flower, because they contain heads without plant material.
• Heat in a sealed container keeps more terpenes than heat in open air. In a sealed container, the air above the rosin saturates with terpenes, thus the net evaporation stops. In open air, the oxygen causes oxidation of the terpenes and the air removes them^[13]. The lightest monoterpenes have the highest rate of evaporation. They go out of the rosin first^[16].
• Only THCa can crystallize into diamonds. After decarboxylation to THC, it stays liquid^[5]. For vape cartridges, full decarboxylation is necessary. For diamonds, the THCa must not change.

Conditions for the values in this paper

• You make the hash correctly and you dry it correctly (with a freeze dryer or with cold air) before you put it between the plates.
• Your press keeps the temperature accurately (PID control or control from an app) and applies the same heat on all the area of the two plates.
• Your work area is clean and cold, and you record your runs. Thus you can change one control at a time.

Unknown properties that change the correct values

• Size and range of size of the trichome heads. They are different for each cultivar. They have more effect on the micron than all other properties.
• Quantity of lipids and waxes. It is different for each type of genetics and material. Flower contains more than hash.
• Crystallization. The ratio of terpenes to THCa sets if diamonds crystallize easily or not easily.
• Accurate moisture. A change of a small number of percent in RH changes the flow, the clarity and the risk of a blowout.

Four connected press balances

As in a grow room, the press has a small number of connected balances. When you change one control, the other controls change.

Press controls

This section gives all the controls in groups. The groups are in the same sequence as the steps. The controls before the press set the maximum quality. The press controls set the balance of yield and quality. The controls after the press set the texture.

Material controls (before the press)

Press controls

Controls after the press

Matrix of the effects of the press controls

This matrix shows the effect on each result when you increase a press control (for the micron, when you use a smaller micron). It shows the direction of the effect, with all other conditions the same. ↑ = increases, ↓ = decreases, → = small change, ⚠ = the risk increases.

The primary information is this: temperature and micron are the controls for quality. Pressure and time are the controls that complete the flow. Use heat and the screen first. Use force only to complete a flow that the heat started^[2].

Matrix of symptoms and controls

Examine the result and find the control that has an incorrect value. Make one correction. Change only one control in each run. Thus the cause of the next result is clear.

Example: one change of the plate temperature

One small change causes other changes. Use full-melt fresh-frozen hash and increase the plate temperature from 71 °C → 77 °C (160 °F → 171 °F). Keep all other conditions the same.

Control that you change

Plate temperature +6 °C (+11 °F). The temperature is in the range for hash (60 to 77 °C / 140 to 171 °F). The bag is 36 µm. The ramp is slow.

First effects

• The viscosity of the resin decreases. The seam of the bag becomes wet after a shorter time, and the oil flows more quickly.
• The yield increases. Less oil stays in the puck.
• The risk of a blowout decreases by a small quantity. The oil has a low viscosity and flows out before the pressure becomes high.

Secondary effects

Pressing methods for each step

This section shows all the steps from the plant to the dab, one step at a time, with the important values for each step. All the steps before the press are steps of the cold chain. In these steps, heat decreases the quality.

Harvest and trichome maturity

The harvest sets the maximum quality for all the next steps. The usual target is 80 to 90% cloudy capitate-stalked trichomes with 10 to 20% amber and no clear trichomes. This range is only a target. You can use other values. Hash makers frequently use less amber, because amber heads give rosin with a dark color and a greasy texture.

Many growers harvest at lights-off, but no known data show that a harvest at lights-off is necessary. For dry sift, harvest when the maturity of the trichomes is a small quantity lower. Stalks with too much ripeness break easily into small pieces. These pieces are contaminants^[10].

Fresh-frozen material, or dry and cure

• Fresh-frozen material (for live rosin and ice-water hash): Freeze the material immediately after you cut it. Do not dry it. This keeps the ‘live’ monoterpene profile. The press temperature for this material is the lowest, and the rosin has the highest purity.
• Slow dry (for dry sift): Hang each plant at 15 to 18 °C (59 to 64 °F) and 55 to 60% RH, in full darkness, with a light airflow. Keep the plant there for 10 to 14 days. The stems must break and not bend. The water activity must be 0.58 to 0.62 a_w (the safe range is 0.55 to 0.65, and 0.55 is the limit of too dry). Then freeze the material after trimming for 4 to 6 h (24 h is best). The stalks then break easily^[10].

Ice-water wash (cold chain)

For bubble hash, mix fresh-frozen material in water that is almost frozen. The trichome heads break from the plant and fall through a stack of micron bags^[14].

Alternative: dry sift (cold chain)

Do not use water. Do the work in a cold room (less than 10 °C / 50 °F). Use a card to move the frozen material across a stack of screens, from large holes to small holes. Use a light force for 3 to 5 min for each pass^[10].

• Screen stack: a work screen of 140 µm (110 LPI), a screen of 107 µm, and the primary screen of 70 µm (200 LPI). The material that falls through the 70 µm screen is edible grade. Heads of 70 to 120 µm are the best.
• Static glove method: Make a glove of black nitrile cold in a freezer and use it on a 70 µm (200 LPI) screen. Move the glove in smooth circular movements, a small distance above the screen. The static charge lifts clean heads and the contaminants stay on the screen. Remove the heads from the glove, make the glove cold again and do 3 to 5 passes. Do not push the glove on the screen^[4].

Drying of the hash (cold chain)

• Freeze dryer (lyophilizer), best method: Set the condenser to −40 to −50 °C (−40 to −58 °F). Set the vacuum to approximately 100 to 200 mTorr (a pressure of less than approximately 500 mTorr is sufficient). Dry for 24 to 48 h, until the hash is fully dry. This method removes water without heat or oxidation.
• Cold air drying (low cost): Use a microplane to put small pieces of the patties on parchment or screens. Dry them in a cold room for 24 to 72 h. This method has a higher risk of oxidation and contamination. Examine the hash for mold.

Grading and moisture conditioning

Melt a sample of the hash on a hot nail and give a grade of 1★ to 6★ (6★ = 95%+ heads, full-melt). The grade sets the products that you can make. It also sets how small a micron and how low a temperature you can use. Make the hash and the bag cold before pressing. Cold material in the bag gives a smaller number of blowouts.

Pre-press and bag load

• Put 2 to 7 g (0.07 to 0.25 oz) in the inner bag. Fold the open end two times. Do not fill the bag too much. Keep space for the flow.
• For diamonds, mechanical separation, and each run with a high risk of a blowout, put the inner bag in an outer bag of 120 to 160 µm.
• For flower and dry sift, make a puck with high density and no air (a pre-press puck). The puck stops channels. For full-melt hash, do not do a pre-press with heat. At most, make a puck with a light force and without heat, to compress the load. Material of high grade flows without a puck.
• Put the bag in folded parchment. The open seam must point to you.

The press

1. Close the plates on the bag, or almost on the bag. Apply heat for 30 to 60 s with no pressure.
2. Increase the force slowly in 15 to 20 s. Examine the seam. The seam becomes wet and the oil flows.
3. Hold the target force for 60 to 120 s (a maximum of 180 s), or until the flow stops. Press until the flow stops, and not to a number^[2].
4. Release the force. The yield from clean 5★ to 6★ input is usually 60 to 80%^[3]. If the yield is less than 50% with good input, a step before the press is incorrect.

Collection (cold chain)

Collect the rosin immediately with a cold dab tool on new parchment. Then put the rosin in glass that is cold and seal the glass. A cold collection keeps the terpenes and sets a clean texture. Go immediately to your product pathway.

Effects of the equipment

Each tool has different controls. Select the press type for the size of the batch. For work at a low temperature, select a press with accurate temperature control.

Press type

Plates, bags and equipment for the cold chain

Matrix of the input and the trichomes

Examine the material with a loupe or a microscope. Then select the settings for the material that you see. The head size and the unwanted material set the micron. Do not select a small micron only because it is small.

Product pathways after the press

The same new rosin from the press changes into each solventless product, through the controls after the press. The press setpoint sets the oil at the start. The cure sets the product at the end.

Frequent problems

Sequence of the press controls

Set the controls in this sequence. Each step sets a limit for the next step. If you do not do the first steps, the next steps cannot give a good result.

1. 1
   Set the maximum quality of the input first

   The genetics, the harvest maturity, the quality of the wash or dry sift, and the moisture set the maximum. You cannot get good rosin from input of low quality with a press.
2. 2
   Select the product

   The alternatives are badder, live rosin, diamonds, a vape cartridge or a hash hole. This selection sets the temperature range and the cure.
3. 3
   Select the micron from the head size and the contaminants

   Large, clean heads: use a larger micron. Small heads or small particles: use a smaller micron. Do not select a small micron only because it is small.
4. 4
   Set the temperature range for the material and the product

   Select the lowest temperature that lets the oil flow. The temperature for hash is low. The temperature for flower is higher. For material with degradation, the temperature is higher than for flower.
5. 5
   Increase the pressure only to get the flow

   Heat is first. Force is second. The pressure only completes a flow that the heat started.
6. 6
   Collect the rosin cold, then do a cure to get the texture

   A cold collection keeps the terpenes. The cure (cold, warm or in stages) sets if the product is badder, sauce or diamonds.
7. 7
   Storage and check of the results

   Keep the rosin cold, with no light, in a sealed container that does not let air in. Record the yield and the grade. In the next run, adjust one control.

Troubleshooting

The table gives the symptom, the possible cause and the first checks. Start at the top of the table. Most problems are in the steps before the plates.

Control of the rosin procedure

The most important information is the sequence:

Use heat for the flow, the screen for purity and the pressure only to complete the flow. Then do a cure to get the texture. The steps before the press set the quality. The press can only keep the quality or decrease it.