9.4.7.1 QWET

 Quick Wash Ethanol is an extraction process by which we freeze the material and chill the Ethanol before extracting, so that we limit the pickup of water, anthocyanins, and water soluble alkaloids, as well as >C-30 and through C040 and C-55 sized molecules like carotene and chlorophyll.  We've used the process both to make oral meds, as well as dabbing concentrates for vaporization.

In addition to locking up the interior of the plant in ice, and lowering the solubility of the heavier molecules, it lowers the dielectric index (polarity) of the ethanol.  See: http://www.ddbst.com/en/EED/PCP/DEC_C11.php

The two processes start out similar, but diverge during purging, as one requires decarboxylation and the other requires remaining in the carboxylic acid state.

We typically perform a QWET at around 0C/-18F, with a starting soak time of three (3) minutes, but keep an eye on the color and base the actual time of real time observations.  We typically use two soaks, and extract 75 to 80% of the essential oils the first and the balance the second.  We use a microscope to tell when the trichomes heads are all gone, leaving only the stalks.

As the second extraction will be more sedative than the first, we usually keep those two extracts separate.  We also sometimes do a QWET first extraction and finish up with a non polar process like BHO.  We will typically yield an additional 5% or so by that method.

The first preparation step is to reduce water content.  The material doesn't have to be desiccated, but we like to pull off the fan leaves and hang our plants 5 to 7 days before freezing.  At that point they are still highly aromatic, but the small stems will snap when bent.

We then break the buds up by hand or by scrubbing through a 3/8" to 1/2" mesh and pack them into the soaking container loosely, about 75% full, install the lid, and stick it in a -18C/0F freezer overnight.

 

Nug Buster

Processes running mostly trim or fan leaves, to be used for oral and topical meds, may call for further water reduction, so for those we spread the material on cookie sheets and place them in a 200F oven until they are just frangible when rolled between finger and thumb.

We don’t want it any drier than that, because it gets dry and dusty, and there is no water left to freeze and hold the water solubles in place.

We then reduce them to about 10 mesh, by scrubbing them through a 10 mesh strainer using our hands wearing leather gloves.  A pasta strainer works perfectly for this task.

We never use a coffee grinder or food processor, as it makes too much dust.

 

Oven Drying 

In both cases, the processed material is packed into a jar about 75% full and placed in a -18C/0F freezer overnight, along with enough 190 proof ethanol for two complete washes.

The next morning, we fill the jar of frozen material to about an inch of the top of the jar with -18C/0F Ethanol, shake lightly, and place back in the freezer.

 

Chilled Ethanol added to frozen material

We take it out of the freezer and shake it lightly again in about 2 minutes and again at 3 minutes when we check it for color.

The object is to soak as long as possible, but stop soaking before the solution begins to green from chlorophyll pickup.   If you can't discern the color with the plant material in solution, pour off a small sample to inspect.  More on green color later.

When the soak is over, we dump the liquid through a rough strainer to separate it from further contact with the plant material as rapidly as possible, followed by further filtration through either a commercial coffee filter or vacuum filter it using a #1 lab filter.

We typically don't press the plant material to exude more alcohol, as it is soaked into the material and is rife with stuff from inside the plant cells.

We stick it back in the freezer for a subsequent second extraction, or aside to dry if using a non polar second extraction.

 

First quick drain through strainer and Chinois

 

Filter using commercial coffee filter

At this point, you get to see what'cha got, because there is no plant material present to add a green hue.  Below is one of our 3 minute soaks running flowers.

 

Amber 3 minute extract, ready for reduction

Once the material is at -18C/0F again, a second QWET extraction can be made exactly like the first except for time, which may be less than 3 minutes, so visual observation works best. 

A real surprise is in store for you if you choose to run a third extraction using plain water to capture the remaining alcohol, which has target elements in it.  Just fill the jar of material still wet from the alcohol with water, shake well and dump it through the screen as before, and filter just like the alcohol extractions.

We will get into alcohol and water removal as a separate subject, but when you reduce the water solution, you end up with more polar anthocyanin color pigments, so once the water alcohol mixture is reduced, the product left behind is red in color.

Sometimes perfection is illusive and in our pursuit of maximum yield we end up with a green solution, which if it isn't toooo green, can be turned to yellow or amber by sticking a clear container of the solution in bright UV light or sunlight, which breaks down the chlorophyll into Pheophytin and allows the amber colors from carotene and anthocyanins to show through.

It helps with the color, but not the harshness, as the Phenophytin biproduct of decomposition and some carotene are still there.

The next step is to remove the Ethanol and there are several ways to do that, but the simplest for ma and pa is to either evaporate it away over low heat, boil it off to atmosphere, or distill it off to recover the alcohol.  The planned end use of the product usually determines that.

If you are making oral meds that require decarboxylation anyway, then there are no concerns using 78.37C/173.1F to simply boil it off, or boil it off in a still.

On the other hand, if you covet dabbing products in carboxylic acid state (shatter), evaporating the alcohol off in a casserole dish or pie plate over 135F heat is a better option.

For material that will be decarboxylated anyway, the simplest way is to boil it off.  Once the alcohol is all gone, you can leave it where its at and continue on to decarboxylate.

For getting started, the cheapest way I found, was to use a Cuisinart fondue pot of canola oil at 250F for even heating.  I put the solution in either a beaker or a stainless bain marie container, which I place in the hot oil and boil off, as well as decarboxylate in one step.

 

Boiling off in hot oil bath

Above I’m using the amboo skewers to induce boiling by acting as points of nucleation and note the jar lids keeping the beaker off the bottom.

 

 Quiescent oil.

 

 Finished Oil.

 

 Next step up is recovering the alcohol using a still, and you can buy counter top Megahome alcohol stills off the shelf:

 

Megahome countertop still

 

For a DIY, I made my own boiler out of a asparagus steamer pot, using a copper coil in an ice water bath for the condenser.

Here is the boiling flask, which is made from an All Clad asparagus steamer, adding an o-ring to the lid, drilling the handles to hold the white oak top beam, and a bulkhead fitting with a hose barb in the lid.  See my article on home made stills for more details:

 

Asparagus steamer DIY still

 

Here is my condenser made from a copper coil inside a stainless salad bowl full of ice water.  The coil feeds through the bottom of the bowl using an o-ring bulkhead fitting.

The bowl rests on a scientific grade cat litter bucket that I had my way with using a jig saw, and discharges into a repurposed empty 1.75 liter Clear Springs 190 proof bottle.  

 

DIY condenser with cat litter bucket stand

 

DIY Still in action

 

The connection hose is a fuel hose compatible with ethanol.  Tygon tubing is not.

Another option is a rotovape, and recommend you read 11.4  Evaluation of Heidolph Instruments Hei-VAP Precision ML G3 rotary evaporator.

The simplest way that I've found to remove the alcohol, while retaining it in carboxylic acid form, is to evaporate away most of the alcohol in a Pyrex casserole dish or pie plate.  I do so by placing the vessel on a heat mat, which I keep at about 135F and let the alcohol evaporate away naturally.

After the concentrate turns into a thick syrupy resin, if you take it off the heat and set it aside covered, it will eventually hardens into shatter.

 I typically evaporate away most of the alcohol and then stick the vessel into a vacuum oven preheated to 125F and once it is up to temperature again, bring up the vacuum until bubbling occurs, and controlling the level of bubbling with the vacuum control.  I take it out once there are no more solvent bubbles at 135F and 10,000 microns/-29.5" Hg.

 

Vacuum purged QWET

 


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