Step 1 - Wash

Step 1 - Wash

Introduction 

Solvent extraction involves washing the plant material to dissolve the wanted compounds. The problem is, many unwanted compounds come along for the ride. Alcohol is known as a untargeted solvent, meaning it will dissolve all non-polar compounds and some semi-polar and polar compounds. The cannabis industry is full of different ways to efficiently wash the plant to achieve certain goals all the while trying to avoid unwanted compounds. 

In the early 2010s, Graywolf introduced QWET and QWISO quick frozen wash procedure for both Ethanol and Isopropyl. These wash procedures have been the mainstay in the cannabis world for creating wax free oil. His procedures perform a simultaneous frozen extraction with short soak times to avoid chlorophyll. (Chlorophyll is what gives the wash a green color). In the RxCE process, washing the plant is separate from winterization. This way, each can be independently optimized.

Washing the plant is a bit more involved than just pouring alcohol over and collecting the runoff. In the cannabis industry tech forum Future4200.com, a discussion on yields established a simple optimal wash that results in high yields. The first 80% is easy. Its the last 20% that becomes exponentially harder. Best extraction techniques at industrial scale result in 98% cannabinoid extraction. Single washes can be as low as 50% extraction. Performing a proper wash will result in much higher yields as seen below. 

Procedure Summary

RxCE uses multiple fast washes with fresh alcohol with each wash. Perform 2-3 fast one minute room temperature high agitation washes. There can be colored plant debris, but the final liquid color should be clear. Stop if the wash is turning green. This means the alcohol is now penetrating the plant dissolving the chlorophyll into the wash. Never soak longer than 15 minutes. All lab tests indicate a lower potency as more plant material gets dissolved in the wash.

1. Place the plant material in a jar. The jar should be 3/4 full giving enough room for strong agitation.

2. Pour in enough alcohol to cover the plant by 25mm/1 inch deep.

3. Shake the jar hard for 1 minute. 

4. Pour the solvent through cheese cloth or a mesh lid to keep the plant in the jar for another wash.

5. Repeat until the solvent is crystal clear with only floating debris.

6. Next, pour the wash through a linen-like paper napkin 

7. Next, pour the wash through a 1.5 or 3 gallon BUNN coffee filter.

8. Discard the spent plant.

The Full Procedure

#1 - Choosing Your Plant Material

The best material are dry cured buds that have not been abused in trimming, IE, the trichomes must remain undamaged. The color of the trichomes will dictate the initial color of the extracted oils. Processed plant sold in retail can be used, but it most likely will give a lot more amber color to the end product. Older plant tends to oxidize and reflect a reddish amber color. Below are three types of plant material from the best to the ho-hum. In all cases, the plant material must be dry when performing the wash. 

#2 - Preparing Your Plant Material

Cherry-pick the best buds and carefully disassemble the buds into little popcorn buds. Large buds must be broken down into little nugs to allow full contact with the alcohol. The easiest way is to break the bud apart by snapping the stem which will cause the larger nug to fall apart into smaller nugs. Using this approach, you can dissasemble the whole bud into little 1/4" mini buds without causing damage. DO NOT SHRED, CHOP, OR MUTILATE. Doing so will allow the solvent to penetrate the plant and pull more color. Shredding the plant material introduces sub-micron plant particulate which causes problems down stream. Be gentle with the plant, it will make life easier.

#3- Washing Your Plant Material

For optimal extraction, 99% alcohol is highly recommended to avoid water content that allows the alcohol to penetrate the plant and dissolve unwanted compounds. Alcohol with minimal water content, such as 95% Ethanol and 91% Isopropyl, are a fine second choices. 

#4- Filtering Your Wash

After washing the plant, the alcohol wash is going to be murky due to the presence of plant and trichome debris. You can use a wire mesh lid or cheese cloth to pour out the wash while retaining the plant material. To remove the smaller debris, pour the wash first through a linen-like paper napkin. Next, pour the wash through a BUNN 3 gallon coffee filter. Pictured below is just a No.6 coffee filter. The bigger the coffee filter, the better because this increases the filter surface area that allows faster filtering. If unavailable, then a  No.4 or No.6 paper coffee filter can be used. The linen-like paper napkin catches the particles down to about 45 microns. The paper coffee filter traps particles down to about 20 microns. Finer filtering down to 1 micron requires synthetic filter media or buchner vacuum systems. These will be covered in the Shop Manual Fast Flow Filter Setups.

Thoughts on Solvents

The RxCE process has two wash/reduction cycles. The first wash cycle is the bulk extraction with subsequent boil down. The second cycle uses Ethanol to redissolve the collected oil, winterize it, then boil down to final oil. The RxCE process is solvent agnostic. You are free to use the solvent of your choosing for the bulk extraction. Depending on your local laws, you may use one of the four solvents seen below. The use of Ethanol or a combination of Ethanol and another is at your discretion. You can have peace of mind that this process has been engineered to produce safe consumable oil. The double reduction described herein acts as a virtual firewall against residual solvents. Lab tests prove the point by consistently reporting no residual solvents.

Table of Solvent Properties - The Four Solvents and Safety Data Sheets Plus Plastics Chemical Resistance to Solvents

                      FDA    FDA GRAS  Dialetric   Boiling    Flash    Forms    Miscible      Chemical Resistance

            Class   Rating   Constant*1   Point     Point    Azeot.   W/Water    Nylon PP    PE    PET  HDPE

Ethanol       3       Y       24.3      78c/173f   14c/57f      Y        Y         A    A     A     A     A

Isopropyl     3       Y*2     18.2      82c/180f   11c/53f      Y        Y         D*3  A     B     A     A

Acetone       3       Y*2     20.7      56c/132f   -18c/0f      Y        Y         A    A     B     D     D

Ethyl Acetate 3       Y*2     6.02      77c/17f    -4c/24f      N        N         A    A     C     D     D

Further Reading on How to Understand Safety Data Sheets. 

*1 Dialetric Constant - The higher the #, the higher the polarity.

*2 Semi-GRAS approval given for limited uses.

*3 SDS conflicts. Half rate an A, half rate a D.

Chemical Resistance:

Types of Plastics:

Nylon, PP=Polypropylene, PE=Polyethylene, PET=Polyethylene terephthalate, HDPE=High Density PolyEthylene,

Ratings:

A = Excellent.

B = Good -- Minor Effect, slight corrosion or discoloration.

C = Fair -- Moderate Effect, not recommended for continuous use. Softening, loss of strength, swelling may occur.

D = Severe Effect, not recommended for ANY use.

N/A = Information not available.

The Importance of Solvent Classification

The US Food and Drug Administration has a 3 level classification of solvents based upon toxicity. This 3 tiered classification is designed to protect you. Here are the three classes, from worst to best. 

Class 1 solvents are known to be carcinogenic. Benzene, a popular industrial solvent is a Class 1 carcinogenic. A recent recall of hair straightening products was due to the Benzene left in the product during manufacturing.

Class 2 solvents are known to have severe toxicity.  Methanol, wood alcohol, is a Class 2 solvent. Methanol will make you go blind or lead to death if consumed in small quantities. 

Class 3 solvents have very low toxicity and are tolerated by the body. Trace quantities are known to be safe. Your body actually produces Acetone, so that's the safest solvent of the four. Don't be confused in thinking just because you can drink Ethanol, that it's safe for your body. It metabolizes into a DNA damaging compound which is why moderate to heaving drinking is a long term health hazard. You should not be drinking any of these solvents. I like to say, "If it trickles down your throat, it can hurt you. Don't do that!". The reality is, RxCE final oil doesn't have detectable traces of alcohol in it as shown in 4 lab tests. All four of these Class 3 solvents are biologically safe in trace quantities.

The main thing to remember about RxCE, it effectively has two washes and two reductions. It's this double reduction that eliminates the excess solvent down to undetectable levels. 

Recommended Bulk Solvent.

Ethanol wins the popular vote for being fully GRAS rated but what people don't know is that ethanol breaks down into carcinogenic metabolites. Drinking is well known to have long term health consequences such as Cirrhosis of the liver, cancer and birth defects. Ethyl Acetate inherently shares this metabolic pathway, thus has carcinogenic metabolites as well. Isopropyl is the second most common solvent used in cannabis extraction with Acetone right behind. Did you know, Acetone is the most bio-friendly of the four solvents? Your body generates Acetone when breaking down lipids. Isopropyl is metabolized into Acetone, a ketone, which is used as an energy source or expelled via breath or urine. All these solvents have either a full GRAS rating or Conditional GRAS rating with limited food application.

In terms of chemistry features, Ethyl Acetate presents the best theoretical working solvent for extraction with the lowest polarity, but is vastly more expensive.This solvent is not miscible with water so you can wash the plant, add water, shake, then the Ethyl Acetate will rise to the surface with all the cannabinoids and leaves water soluble compounds in the water. There's no straining or filtering needed, its all done for you through chemical reaction. The down side is, by boiling Ethyl Acetate in water, Ethyl Acetate breaks down into Ethanol and vinegar. Vinegar is not a problem, it will be discarded with the waste water and you can recover the ethanol, but not the very expensive Ethyl Acetate. That is a lot of money for a one time use.

Acetone, as mentioned above, is actually the most bio-friendly down at the trace levels, but has very low flashpoint and boiling points. Isopropyl alcohol is more suited for extraction because it has an near identical flashpoint and boiling point to Ethanol. The best part, it metabolizes into Acetone thus becomes bio-friendly in residual quantities. Isopropyl is favored here for the bulk extraction because of its unique chemical features being approximately 20% less polar than Ethanol, thus faster in dissolving oils. Isopropyl is available in safe USP-NF grades and is about 1/4th the cost of heavily taxed Ethanol.

The more expensive Ethanol takes longer to dissolve oils due to it's higher polarity. For this reason, this process highly recommends using 99.9% USP-NF grade Isopropyl for the bulk extraction. 91% Isopropyl works fine but with the small water content, may pull a bit more green color. 

Isopropyl is very efficient in dissolving non-polar oils in very short order at room temperature. Longer soak times at room temperature only allow more unwanted polar plant material to be extracted. Here are the wash times reported by Gray Wolf in his QWISO extraction post:

With a dielectric index of 17.9, versus Ethanol's 24.5, Isopropyl is less polar, yet is still much more aggressive in extracting both targeted and un-targeted elements. Where we start a 3 minute soak with Ethanol, starting point with Isopropyl is 20 seconds.

Like Ethanol, we address it using subzero extraction temperatures, and address the aggressiveness issue by shortening soak time. We typically yield 75 to 80% within 20 to 30 seconds, and pick up the balance using a second soak.

Obtaining and Using Highest Proof Ethanol.

If you use Ethanol throughout the process, it's best to use 190 Proof/95% ethanol. Lower proof alcohols contain water that interferes with dissolving the oils. 

First approach - Using lower proof alcohols

If 190 proof ethanol is not available in your state, you can use lower proof down to about 120 proof. This will take a lot more alcohol and time to dissolve the oils, so heating up the alcohol to about 37c/100f will help. Do not go higher than 43c/110f or the warm temperature will dissolve more plant material. You can heat up the alcohol by placing the container in a sink of hot water.

Next approach - Using a moonshine still to condense the alcohol

Depending on your state's laws, owning and operating a moonshine still to concentrate the alcohol may be legal. Here is the most important point. You will not be generating new alcohol. You will be removing the water. This is legal in most states. Use a moonshine setup like the one listed on the RxCE equipment list page for condensing your alcohol. You can take 80proof/40% vodka and concentrate it to 190proof/95% in a single pass. The trick is to stop distilling once the rises to 85c/185f.  Watch the temperature gauge closely. Once the needle hits 85c/185f, swap capture jars.  The first jar will contain 95% ethanol, the second about 70% as it collects more water. Save that second jar for future distillations. You can turn off the heat when the temperature reaches 200f.

Do your homework. Find out if this is legal in your area before proceeding. If not, then use the highest proof available but you might have to heat it up to 37c/100f. Do not overheat the alcohol, you'll end up with water only. 

The Art of Golden Oil

There is a preoccupation with making clear golden cannabis oil as seen in vape pen carts. The options for making golden oil in the kitchen are limited. The problem being, exposure to the atmosphere allows the oil to oxidize into a reddish color. This oxidation is synonymous with apples turning brown, or bananas showing bruises. In order to avoid turning color, the oil must be isolated from the atmosphere by vacuum systems or flooding  the airspace with inert gasses like nitrogen.

Most golden oil you see in vape pens are distillates created with closed loop BHO or Supercritical C02 extracts as starting points. These extraction systems produce rough golden oil  which require additional cleanup before being turned into a distillate. Even then, if left open to the atmosphere, the oil will turn red on its own. Here are a couple examples where the oil turns color on its own. The left in a vape pen and the right, production grade oil at a lab.

Moving Forward!

To make golden oil, all the pieces of the puzzle must in place. You must start with the right plant material, perform an appropriate wash, then boil off the alcohol in an oxygen free environment. Vacuum systems like the Source Turbo or EtOH Pro can facilitate alcohol removal. At ambient atmospheric pressure, nitrogen gas can be used to supplant  the oxygen. Both of these approaches take additional hardware. 

The first challenge is acquiring the right plant material. It takes recently harvested and cured plant material to get close to golden oil. This is extra difficult for consumers at the end of the supply chain. The time difference between the growing field and the extraction makes this impractical, if not impossible. 

The second challenge is to employ an optimal wash, ie, quickly wash the plant to dissolve the surface trichomes. The goal is to avoid unwanted green color. Several one minute room temperature high agitation washes gives you optimal contact time without deeply penetrating the plant. The resulting wash will look amber instead of green. Avoiding the green color up front saves a lot of trouble trying to remove it later. The process to remove chlorophyll color requires lab gear and filtering media. It can be done at home, but is really beyond the scope of the kitchen. 

Do not do long soaks! Long soaks only dissolve more unwanted compounds. Frozen washes have been used for this in the past but this requires freezing both plant and alcohol in order to wash it at temperatures below -20c/-04f. By washing the frozen plant with frozen alcohol, alcohol is restricted from penetrating the plant where most of the chlorophyll resides. The frozen waxes continue to provide surface protection. Standard consumer freezers will get you down to -20c/04f, but it takes 12-24 hours to do so. This is the industry standard approach to Winterization introduced by Gray Wolf in his QWET and  QWISO processes. (Note: RxCE using Rapid Winterization so there is no need to freeze your plant and alcohol up front. 'Step 3 - Winterization' goes into depth on how this is done.)

If your wash is green, the next challenge will be removing the heavier chlorophyll molecules with a lab vacuum setup. Oil must be vacuumed through a bed of activated charcoal and diatomaceous earth filter media using a buchner funnel setup. This is classic Color Remediation but is beyond the scope of the kitchen gear but is easy enough to acquire. You can find all the right consumer lab gear available on Amazon if you wish to take the plunge. Save yourself the trouble by doing fast washes with lots of alcohol.

Looking forward, once extracted, the last challenge is removing the alcohol in an oxygen free environment which avoids turning the oil red through oxidation.

So lets put this all together. There are very specific things you must have to produce golden oil. First off, your plant material must be harvested before the trichomes turn amber, then cured.  The selected solvent should optimally be 99% alcohol to extract only the surface resins without penetrating the plant. The more penetration, the greener the extract. If all things are equal and you do the proper wash on the proper plant, you can get close to golden oil. All efforts at atmospheric pressure will result in red oil. If you're goal is golden oil, then best to use a vacuum alcohol recovery system like the Source Turbo or EtOH Pro from Extract Craft.

I am going to end the discussion on golden oil here with a promise to further investigate color remediation in the kitchen. Once a satisfactory approach is found, these pages will be updated with any process change. 

Author's Note: Here is what ChatGPT reports about the aged color.

Question: When trichomes age, the oil within turns amber. Is this color chlorophyll? And why does it change color after harvest?

Answer: No, the amber color observed in aging trichomes and the change in color after harvest is not due to chlorophyll.

Trichomes are tiny, hair-like structures found on the surface of cannabis flowers, leaves, and stems. They contain resin glands that produce various compounds, including cannabinoids and terpenes, which contribute to the aroma, flavor, and effects of cannabis.

The amber color in aging trichomes is primarily attributed to the oxidation and degradation of cannabinoids and other compounds within the resin glands. As trichomes mature and approach the end of their lifecycle, the cannabinoids within them can undergo chemical changes due to exposure to oxygen, light, and other environmental factors. This process is known as oxidation.

During oxidation, certain cannabinoids, such as THC (tetrahydrocannabinol), can convert to other compounds like CBN (cannabinol), which is associated with more sedative effects. The amber color is often an indication of higher CBN content and can be a sign that the cannabis has reached a more mature or "ripe" state.

After harvest, the cannabis plant is typically dried and cured. During this process, further chemical reactions can occur, including the continued oxidation of cannabinoids. The exposure to air and the drying conditions can contribute to the color change in the trichomes and the overall appearance of the plant material.

It's important to note that the color of trichomes and cannabis flowers can vary depending on the strain, genetics, cultivation methods, and environmental conditions. Additionally, the effects and potency of cannabis are influenced by various factors beyond just color, including the overall cannabinoid and terpene profile.

References:

Gray Wolf's QWET and  QWISO processes.

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