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Modern Methods

What is Rosin?

Rosin is a cannabis concentrate that can be obtained from cannabis flower, hash, kief, and other solventless cannabis concentrates.  It differs from most cannabis extracts in a couple of notable ways.  

Most importantly, rosin is one of a few cannabis concentrates on the market today that contains the full spectrum of cannabinoids and terpenes found in the starting material.  This is significant because when all these compounds are present, they may provide a user with what’s called the entourage effect.  (Every strain of cannabis contains a particular mix of cannabinoids and terpenes, and these different molecules can trigger different physiological reactions in users.  The entourage effect is the term used to describe the whole set of interactions between these different reactions as they occur inside a person’s body.) Though this phenomenon is not deeply understood at this point in time, it appears to play a role in shaping both the psychoactive and medicinal effects that many people experience as a result of cannabis use.  

Furthermore, it appears that only cannabis products which preserve a relatively accurate “snapshot” of a plant’s cannabinoid makeup and terpene profile, as rosin does, can offer the full force of the entourage effect.  Some solvent-based extracts, especially most commercially available distillates, are not capable of providing a full spectrum experience because these methods can, in different ways, exclude desired compounds from the concentrate.

Another distinguishing feature of rosin is that it contains fewer impurities than most other solventless concentrates on the market.  This is because it’s extracted through a fine filter using a combination of heat and pressure, literally by pressing the starting material between two heated plates.  (Parchment paper protects the starting material from ever coming into direct contact with the hot surfaces.) Other solventless concentrates, such as hash or kief, contain more unwanted organic plant matter than rosin due to the methods used to extract them.  

It’s difficult to obtain a relatively pure solventless concentrate through conventional methods because cannabinoids and terpenes are most densely concentrated in essential oils inside the trichome  heads that line cannabis flower.  In order to collect these trichome heads in a concentrate, they must be separated from the plant and then fed through a filter to strain out unwanted plant matter.  Any filter used for this purpose must have a mesh size large enough to permit these plant structures to pass through. However, other plant fragments (e.g. cystolithic hairs, trichome stalks and other cellulose material) that are too fine to be strained out also slip through these filters.  Rosin extraction sidesteps this challenge by temporarily rendering the oils inside these trichome heads more fluid, allowing them to pass through significantly finer filters that are much more effective at holding in unwanted organic matter. This ultimately results in a less contaminated final product.

On the other hand, solvent-based extraction techniques can leave behind unevaporated solvents in a concentrate.  What’s more, decarboxylation as well as terpene loss can take place if solvents are removed using a heat-based evaporation procedure.   

Decarboxylation is a form of molecular degradation in which a molecule loses a carboxyl group.  In this case, THCa, a cannabinoid found in many strains of cannabis, is exposed to heat and consequently degrades into two molecules, a carbon dioxide molecule which separates from the concentrate and a ∆9-THC molecule, which is psychoactive.  This is not a problem if the ∆9-THC is consumed orally or topically, but most cannabis aficionados agree that for an optimal smoking experience, the THCa molecules should be kept intact until the moment they are to be smoked. If this degradation happens too far in advance, the cannabis product containing the ∆9-THC appears to leave smokers with a lethargic feeling.  Cannabis users who normally feel mentally engaged after consuming cannabis products may consider this effect unpleasant or undesirable. However, many consumers appear to be less concerned about decarboxylation than about terpene loss, which can also result from prolonged heat exposure and may affect a concentrate’s flavor.

So how does rosin, which is extracted via a process that includes exposing these cannabinoids to heat, avoid these pitfalls?  The key is not using too much heat, and supplementing the heat with the right amount of pressure to make the oils in the starting material sufficiently fluid.  The molecules that concentrate producers aim to capture have heat-averse tendencies, meaning that, when mobile, they tend to be repelled away from hotter environments and towards cooler ones.  

The optimal temperatures for extracting rosin vary based on starting material.  These temperatures must be hot enough to render the desired oils mobile (which allows them to flee the heat) but cool enough that all the THCa molecules, except for a negligible fraction, are successfully expelled from the hot environment before they can be decarboxylated.  (In the world of rosin presses, escaping to a cooler environment means moving beyond the edge of the heat plate and accumulating inside the folded parchment paper.) At optimal temperatures, most terpenes in the starting material are retained, whereas certain other processes may cause them to be off-gassed or degraded.  Immediately after pressing rosin, a good producer transfers the parchment paper containing the freshly extracted substance to a cooler environment (e.g. underneath a cooling disc) to prevent decarb as a result of residual heat.  

A list of optimal temperatures and pressing times, broken down by starting material, is included in Part 2 of this document, under the Rosin Extraction Techniques section.  Research data on cannabinoids are scarce because of legal restrictions on cannabis research, but according to two studies, neither of which was conducted very recently, “the THCA decarboxylation reaction starts at 90 °C.”  Anecdotally, people in the cannabis industry have reported observing THCA decarboxylation at significantly lower temperatures.  Decarboxylation rates rise along with increases in temperature, though the exact relationship between these phenomena will probably become clearer as more research is conducted.

 

What are the different varieties of rosin?

Over the past few years, a standard has emerged in the budding rosin industry to categorize batches of the concentrate in terms of two fundamental characteristics.  The first is starting material, which can be flower, hash, kief, and fresh frozen hash.  (We describe these in greater depth below.)  When pressed, these materials yield concentrates called flower rosin, hash rosin, kief rosin and live rosin, respectively.  

The second characteristic is texture and consistency (and appearance, some might say.)   In this manual, we’ll describe the five most common rosin textures: shatter; pull-and-snap; budder; sap; and sauce.  (Readers familiar with solvent-based concentrates will recognize these terms, as cannabis extracts have been available in these textures for some time.)  Rosin comes in other textures as well, but cataloguing them is not our goal here, so we’ll focus on the varieties that are the easiest to find on the market.  

These different textures can be achieved by making adjustments to the extraction process and by employing various post-extraction techniques.  

 

Differences by source material

The first step in extracting standard quality rosin is to pack the starting material into a filter.  We recommend using a mould to shape the material before inserting it into the filter, which maximizes the amount of starting material that can be processed in a single pressing without sacrificing the quality of the final product.  Filters, which resemble teabags, are available in a variety of mesh sizes. The ideal mesh size depends on the starting material; for instance, kief requires a finer filter than flower. Recommended press settings (for heat, pressure and the rate at which the pressure is increased) as well as plate head sizes also vary based on starting material.  For more technical details on optimal heat settings and equipment specifications, see Part 2 of this document.  


Flower rosin:

Mass of rosin relative to starting material: 15%-35%

Cannabinoid volume: 50%-75%

Terpene volume: 1%-6%


Of all the rosin types, flower rosin is the most likely to deliver a full-spectrum experience to users.  

When it comes to producing rosin, the size of a yield always depends on the quality, potency and freshness of the starting material.  This fact is most evident when it comes to flower rosin.  If a batch of flower has a relatively low cannabinoid count, or if it wasn’t grown or cured properly, or if it is no longer fresh, it will yield smaller quantities of rosin, which is also likely to be substandard in quality.  Even if all these obstacles are avoided, there are some strains, such as some OG and citrus varieties, that tend to yield rosins on the darker, sappier side.  Certain other strains (e.g. strawberry banana or cookies and cream) are more likely to yield lighter-colored rosins, which consumers tend to consider more desirable.  

As a result of all these challenges, and because some producers simply don’t how to properly process flower rosin, more than a few unimpressive samples of the concentrate have ended up in stores.  This gave flower rosin an (undeservedly) low reputation, causing it to be less sought after than rosin from other source materials.  In spite of its low estimation in the public eye, however, a good flower rosin could boast yields, cannabinoid levels, terpene levels and even user satisfaction ratings that rival or exceed those of some kief and hash rosins.  


Hash rosin:

Mass of yield relative to starting material: 40%-85%

Cannabinoid volume: 55%-85%

Terpene volume: 1%-7%


Hash rosin is extracted from hashish.  It tends to have a higher cannabinoid volume than flower rosin because in most cases, the starting material--hash--has a higher concentration of these molecules than flower does.  

While hash rosin can be extracted from any type of hashish, it is typically pressed out of hash that was obtained through a special process.  The process begins when flower is deposited inside a set of bags with mesh bottoms; the mesh sizes of each bag get progressively smaller further away from the center.  These bags are partially submerged in a container of very cold water. The flower is agitated to help shake loose the cooled trichome heads, and water helps to transport them through the fine screens at the bottoms of the bags.  Once the trichome heads have accumulated in the bags (different sized heads end up in different bags) they are collected and the hash is dried out.


Live rosin:

Mass of yield relative to starting material: 80%-96%

Cannabinoid volume: 75%-90%

Terpene volume: 3%-7%


Live rosin is typically the most expensive rosin on the market.  While rosin in general is currently something of a luxury product (incidentally, we don’t believe it has to be, but it is right now) live rosin is luxurious even among rosins, often selling at around or upwards of $100/gram in early 2019.  Live rosins are frequently more potent than other rosins.

Above, we noted the importance of using fresh starting material; live rosin takes this concept to an extreme, as it is extracted from fresh frozen hash.   Fresh frozen hash is obtained by freezing uncured, freshly harvested flower, then running it through the process used to make hash (described above.) The material is then usually kept frozen until it is consumed or processed into another concentrate.  

Fresh frozen concentrates generally tend to be less amber in color than their conventional counterparts, and live rosin is no exception.  This type of rosin also tends to come in lighter shades than the others, ranging from pale to transparent depending on a given sample’s texture.  It’s classified as distinct from hash rosin because it tends to be more potent, both in terms of cannabinoid dosage and psychoactive effects.


Kief rosin:

Mass of yield relative to starting material: 40%-85%

Cannabinoid volume: 55%-85%

Terpene volume: 1%-7%


Kief is a collection of trichome heads and other plant matter that have shaken free from flower and/ or “sugar trim”.  Rosin extracted from kief tends to have cannabinoid content levels similar to those found in hash rosins.

Like hash rosin, kief rosin is also a bit of an umbrella category in the sense that there are different kinds of kief rosin.  Rosin may be pressed from simple kief, but kief can also be processed into a purer concentrate known as dry sift, which, when pressed, yields a type of kief rosin known as sift rosin.  

Dry sift can be obtained by placing kief atop one or more fine screens and agitating it so that most of the trichome heads are separated from unwanted plant matter, including pieces of stalk and other cellulose material from trichome heads.  The purest sift rosins can rival live rosin in yield size and cannabinoid content. Sift rosin tends to be slightly darker in appearance than live rosin, but is frequently quite light in color compared to other rosins.

 

Differences by texture/ consistency

Shatter: a rigid and highly transparent concentrate texture named for its brittleness.  Typically sold in thin sheets, shatter is very easy to crack when cool. Where a piece is broken off, tiny fracture lines tend to run through the larger sheet from which it was separated, and small shards almost always break off when one piece of shatter is separated from a larger sheet.  

When heated up slightly above room temperature (e.g. to near body temperature, by pressing it gently between one’s forefinger and thumb) it becomes less rigid and somewhat malleable, so that it can be manipulated without breaking.  Shatter is relatively dry compared to other concentrate consistencies, with a dry-stickiness reminiscent of a jolly rancher’s that increases with temperature. To the naked eye, it appears to have a relatively uniform texture compared to many examples of buddered rosin, in which the concentrate may, to some extent, settle/ crystalize/ organize itself into grains.


Pull-and-snap: rosins of this texture are about as transparent as shatter.  Like shatter, pull-and-snap is also quite rigid at lower temperatures, but rather than fracturing under a relatively small amount of pressure, pull-and-snap allows dull objects, such as a spoon or the blunt edge of a knife, to be pushed through it slowly.  If such an object is wedged into a portion of pull-and-snap rosin and then pulled away quickly in a jerking motion, a piece of the concentrate may stick to the tool and break loose from the main mass.

At warmer temperatures, pull-and-snap gets quite gooey and can be easily stretched out using a tool.  Even in this state, however, an abrupt enough motion can pull free a chunk of rosin.


Buddered rosin: while all the other formats of rosin described in this section are either transparent or translucent, buddered rosins are opaque.  They vary in opacity -- some are lightly opaque while others barely allow any light through at all. When wet, this concentrate has a consistency a bit like freshly made caramel that’s still warm.  It’s also a bit like smooth peanut butter, except that it tends to stick slightly more to itself than to other objects, whereas peanut butter tends to stick indiscriminately to most things. Some wet buddered rosins may be handled directly, while others are very sticky and should only be handled with tools or in a cold environment.  Drier samples of buddered rosin tend to crumble rather than stretch out when manipulated, and they tend to separate into grain-sized clumps of mealy cannabis matter.

The relative wetness or dryness of buddered rosin may depend on how recently it was manufactured (i.e. samples dry out over time) but manufacturers can achieve a drier consistency by agitating their buddered rosin, filling a market demand for easier-to-handle budder.


Sappy rosin: most often, rosins of this texture result from pressing flower.  They range in color from amber tones to almost clear. Their texture resembles that of a thick honey and is about as sticky.  Therefore, it’s advisable only to handle “sap” that’s been brought to a relatively low temperature, and to do so using a tool of some sort.  At room temperature, it pulls apart in gooey strings when manipulated.


Sauce: these rosins tend not to have a uniform texture.  They feature granular, dry, hard clumps of THCA submerged in a soupy matrix that is primarily made up of terpenes.  The clumps of THCA are visually reminiscent of sugar crystals that sometimes form in honey jars, but the matrix is much less viscous than honey.  When rosin sauce is stirred, these granules mix with the low-viscosity matrix in such a way that the material comes to resemble apple sauce. After mixing, these components remain assimilated rather than re-separating.