I ran across this article by Ichiban Crafter and Troy Ivan gave me permission to share it.  More like it at Check out their site at: https://www.extractcraft.com/

He demonstrates an alternative to using a column, by mixing the carbon filtrating material with the solution and then vacuum filtering it out using a poured slurry diatomaceous earth filter bed.

Polishing Dark Extracts:  Carbon Scrubbing & Diatomaceous Earth (DE) Filtering, by Ichiban Crafters

These days everyone is hypnotized by light color extractions even though color alone does not determine quality.  Important quality considerations are actually clarity, cleanliness, aroma, terpene content, and potency.  It’s very possible to have a high quality concentrate that’s dark in color, or a low quality concentrate that’s light in color, so the deliberation shouldn’t be over what color the concentrate is, but why it’s that color.  This post is to help those that have concentrates, or may be making concentrates, that are dark for the wrong reasons and provide a reliable process to improve the product quality.

Everyone has had a wash or end product that came out darker, more green, or containing more undesirables than they hoped or intended.  Questions on how to deal with dark concentrates and extractions come up every day.  The easy answer is to take more care early in the extraction process so the undesirables are avoided altogether, but sometimes it’s too late to avoid and you just want to clean it up and carbon is the easiest answer.  It’s important to understand that when an extract is polished it loses desirable components along with the undesirable, inadvertently removing cannabinoids and terpenes.  Here lies the conundrum, do you accept the extraction as is, or do you polish it and sacrifice some of the desirables? To help crafters make that decision this post will explain a simple way to perform the polishing, using activated carbon powder for scrubbing to lighten the color and diatomaceous earth for very fine filtering, provide a side by side comparison of polished and unpolished results from the same extraction, and look at what was lost in the process.


I used decent quality trim and 190-proof food grade ethanol to make the wash.  Both the trim and ethanol had been in the freezer for a number of days and were between -2°F to -10°F.  To get the green wash I needed I did a 1-hour freezer wash to get some green pickup without going to a full FECO.

Starting Material


The 1-hour wash initial filtering went through fine mesh coffee filters for plant matter separation, then through the Buchner funnel using 3-micron filter paper.  The wash came out with the perfect amount of green and just over 1L in volume.

As extracted


I separated two 300 ml samples from the 1L of filtered wash.  One sample would be processed as is and the other would go through the polishing process.  I will refer to the sample that will be processed as is as the ‘control sample’ and the other as the ‘polish sample’.  The sample size of 300ml was used to match the capacity of the Source Turbo used to make the oil and recover the ethanol.

Split sample


The carbon is essentially charcoal and functions in the same way as a charcoal filter commonly used to purify water.  Carbon powder is really good at removing contaminates from liquids, but unfortunately it does this in a very indiscriminate manner and is difficult to filter out of the wash due to the very fine particle size.

Activated charcoal powder

The carbon scrubbing process itself is nearly as easy as mixing the wash and carbon together and shaking. The process is most effective if the wash is warmed to about 80F before adding the carbon.  The recommended amount of carbon to use is about 5% of the estimated volume of oil that is contained in the wash.  For 300ml wash, I estimated about 3g of oil so the recommended amount of carbon to be used was 0.15g.  I made and error here and added quite a bit more, about 1.5g, but I proceeded and pretended not to notice.  I originally planned to use a stir plate for agitation, but a friend with much experience advised that shaking provides much better results, so I put the wash and carbon in a small jar and gave it a good shake instead. That’s all there was to it and the carbon scrubbing was complete, but the resulting wash was utterly black with carbon and required very fine filtering.


Sample mixed with Carbon


Wikipedia defines diatomaceous earth: “Diatomaceous earth ( /ˌdaɪ.ətəˌmeɪʃəs ˈɜːrθ/) – also known as D.E.diatomite, or kieselgur/kieselguhr – is a naturally occurring, soft, siliceous sedimentary rock that is easily crumbled into a fine white to off-white powder.”

DE Powder 

The DE is a very fine powder, almost like flour, and when mixed with ethanol and properly filtered with a vacuum assisted Buchner funnel will form a filtering cake that makes for very fine filter media.  I layered a Buchner funnel with a 3 micron filter paper, then a coffee filter on top of it to help hold the DE in place and form the filter cake.

To make the DE filter cake I first stirred together the DE and ethanol to make a slurry, that resembled a mud puddle.  When the slurry is poured into the Buchner funnel, with the vacuum assist running, the ethanol sucked through into the beaker and the DE was left behind in a solid cake form.


Add water and mix

Pour DE slurry into Buchman funnel with filter

Draining slurry

The more you pour in the thicker the cake will form.  I don’t know, and can’t find information on, what thickness of the filter cake is ideal, so I made it about a 1/4-1/2 inch thick. I let the cake settle into a solid form then began adding the carbon wash for filtering before the DE cake dried out.

Even with the vacuum assist from a large pump the progress was quite slow, it took about 5-minutes to filter 300ml.  I think this would have worked better if I had used one of the larger Buchner funnels.  The slow progress was no real problem, but the 1L size would have provided more filter surface area and better flow.  That was a good lesson learned here and a point to keep in mind.  Another thing to keep in mind is that the Source Turbo vacuum port can be useful for normal vacuum assisted filtering, but for this kind of heavier work it’s probably not be sufficient.

Pouring carbon mixture through DE filter bed


Recovery stream

The polish sample worked its way through the filtering layers and emerged in the beaker cleaned up and glorious.  When the control sample and polish sample are set side by side the improvement in color is obvious.

Compare carbon filtered, versus non filtered color and clarity.


The processing plan was simple.  First, use the Source Turbo (extractcraft.com) to separate the oil and reclaim the ethanol, then pop the oil samples into the vac oven to finish.  I experienced a small spillage mishap of the polish sample so I evened the samples to 250ml each for processing.  Each sample ran separately in its own Source Turbo for about 2 hours, then in the vac oven overnight at 92F.


The difference in the resulting oils was literally night and day, light versus dark.  Both oils were very clear and clean, the darker oil was obviously carried over the green tinge from the wash, while the blond oil was defiantly pleasing to the eye.

Unfiltered and filtered in vacuum oven on silicone mat. 

Out of the vac oven the completely purged end products finished as expected with the lighter sample as blond as could be and the darker turning out much better than expected.

Samples taken directly from the vacuum oven

Shatter after folding and condensing samples into thicker form

I knew polishing would improve the concentrate color but I didn’t really know what to expect with regard to the how much scrubbing would effect the yield or quality of the final product.  For me, determining exactly how much oil was lost in the process was the most interesting part of the whole exercise.  The control sample was obviously going to be heavier than the polished sample, but by how much?  The control sample was 2.75g compared to the polished sample coming in at 2.26g.  The scrubbing and filtering reduced the yield of the final product by 0.49g or 17.8%.

All of the colored, undesirable material was removed from the polish sample along with a small amount of terpene character.  The darker extract ended up being both, more rich with terpenes and robust, but the green from the wash was identifiable by a faint plant taste. The terpene profile was a little weaker, not by an enormous amount but by enough to note the difference, but the psychotropic effects were notably more potent than the unpolished extract.


That was a lot of fun!  I’ve been wanting to do this project for a while to figure out if carbon scrubbing and the necessary advanced filtering is worth hassle and yield sacrifice.  It is obvious by the results that it works very well to lighten the color and increase potency. So, when are those benefits of better color and increased potency worth sacrificing the 17.8% in yield?

Let’s start with when I would not consider polishing useful or necessary. For edibles, tinctures, or topicals it would not be useful, and I would instead opt for the benefit of maximizing yield over color, taste, and potency.  The color and taste will be diluted by whatever carrier is employed and the potency is easily adjusted by the ratio of oil used.  I would also not consider polishing for a smokable if it were a singular concern over color when all other considerations of clarity, cleanliness, aroma, terpene content, and potency are all acceptable.  We know from by blog post https://extractcrafter.com/2016/11/11/color-and-cannabis-concentrate-quality that dark concentrates can be as good or better as lighter concentrates.

I will only recommend polishing if my wash inadvertently picked up green when I didn’t want it to, or I have an already made concentrate that has an unpleasant flavor.  What I would highly recommend is avoiding the problem from the beginning and use extra caution in careful wash execution, like in my blog post https://extractcrafter.com/2017/06/28/cannabis-oil-qwet-extraction-battle-of-the-wash-dry-ice-vs-freezer.

I hope this post provided some useful insight and  enjoyment.  If you appreciate my work please share  and spread the word!  Stay lifted and blessed.

Leave a Reply