How are 0.08% THC and lower hemp flowers possible?

I’m seeing a lot of cbd flowers on the market that contain little to no thc, yet have 10% or more CBD content. I’ve been looking all over for the strains they are using and I’m ending up with nothing. Do they treat the flowers somehow?


Heard in Switzerland these super low THC CBD flowers somehow get “washed” or heat treated. Not sure about te actual process though.

Haha it’s the Switzerland trick :joy:

Here to down the THC and make it sellable in Europe most of the flowers are wash with butane or ethanol. Some people also apparently used UV to destroy cannabinoids without lost of terps but I’ve never see it by my eyes.

The 2 first methods are the more conventional. Then they put terps back for the smell.

Usually people paid 100€ per KG to downgrade the THC (And the rest of cannabinoids) level with BHO/ETH, and yes … Then people smoke it. The funniest thing is people paid to reduce the cannabinoids level of the plant and at the end you can keep the extract because they don’t know what to do with. Personally I’m happy with that … Free Crude :grin:

I’ve also seen that more and more breeder acheived good results in terms of CBD/THC ratio but not as much as 0.08 THC for 10% CBD.

We work with a strain who generally do 0.8% THC for 15-16% CBD.

Exposition to UVB does the trick. I did some tests and for every 50% of THC reduction there is 15-25% reduction in CBD content.


Interesting. Curious, what kind of UVB exposure, time and wattage wise, do u find neccesary per 50% THC reduction?

The easiest is to dry the crop directly in the sunlight post harvest in a same way as it’s done with hay. A day of direct sunlight more less reduces THC by about 25% and CBD by 15-20%. But that’s an avarage and the more exposed biomass on the top layer will get affected more (so flipping is required).

With an UVB lamp the same can be achieved within an hour. This fairly crappy ratio can be affected by adjusting distance from the lamp, power, moisture level in the biomass and filters.

After 2h under my lamp 50% of THC was gone. I can check it’s nominal power when I get back to the office. I think it’s 60W but I can be wrong.

When THC level is going below 50% of initial level CBD will start breaking faster.


You can make “hot” hemp compliant by UV light exposure on the flower ? :open_mouth: Am I understanding that correctly.

1 Like

Yup. UVB. I’ve tried UVC lamp I bought from a dentist but I just wasted money.

This trick will not work on an extract.

But extract can be “cooled” as well just with different tec.

1 Like

Interesting stuff. I wonder why it won’t work on an extract? I was thinking of doing some rosin from hemp kief. Trouble is, it will def. go over the 0.2% limit in EU if you concentrate it that much. Mind sharing the tec on how you ‘‘cool’’ the extract? I was thinking about diluting it with CBD distillate but that’s not ideal.

All my tests were done with Carmagnola. Hemp that is notorious for going above the legal limit. Without any “cooling” the specs for flower and it’s products were:

  • flower: 9% CBD and 1.3% THC
  • crude: 50% CBD and 7% THC
  • winterised and de-pigmented extract: 69% CBD and 4.9% THC (something affected the ratio. Details below)

Due to a legal loophole in my country hemp extracts are okay regardless of THC content (as long as it’s possible to prove it’s a hemp extract). They are legal to posses but can not be legally introduced to market. (basically the law states that industrial hemp can’t go over 0.2% THC, it’s illegal to harvest rosin from any cannabis plant and it’s illegal to make extracts from a cannabis other than Sativa L.)

So far I have 3 methods that can be used to reduce THC content:

  • UVB (flower or kief)
  • Water/methanol/NaOH solution used for pigment extraction (flower and possibly extract but I didn’t test my latest samples yet) that also pulls THC and CBD but at much slower rate
  • Filtering using heat activated bentonite that is prewetted with 50/50 ethanol/water solution prior to filtering. The extract has to be dissolved in ethanol (will not work with methanol or iso) and mixed with some water.

All methods give 5:3 ratio of THC/CBD removal out of the box. It’s possible to improve the ratio to 5:2 or less.


Looks to me it’s pretty damn difficult or impossible to make rosin then and still have a usable product. I mean even if you go through all the steps. UVB the kief and the other methods you mentioned, I doubt you could get it to 0.2% THC and still have a desirable product. Some sort of dilution will be necessary.

I have 200 grams of distillate with 6:1 ratio. Close to 14% THC. I’m going to use the third method couple of times and see how much I will have to waste in order to get it to a reasonable level of THC.

But yeah, the easiest way is to fix it with UVB. And since I started growing hemp I will have a lot of testing material as it’s a harvest time here.

Sorry for reviving an old thread but i’ve got to ask. A friend of mine grew legally CBD plants but the problem is the outrageously low THC limit of 0,2%. After he completed the harvest he sent samples of the buds for lab analysis and results came back showing 0,6% THC and 13% CBD. Now he cannot legally sell those flowers.

He read about UV lights being used to lower THC concentrations…? Does any of you guys know more about the subject? Anyone who has tried it perhaps? Thank you very much for any answers.

To get these zero or low thc results they test hemp samples Prior to flowering
Then only report d9 thc not thca
And also use loq and Lod are higher than normal so you don’t detect or quantify what is there


@elchemy makes a good point, this is usually where regulators in emerging markets get the 0.2% THC interpretation wrong. Anyone have a publication discussing this in more detail?

Thank you for the answer. So at this point there is not anything my friend can do but try to reduce the THC concentration through UV bulbs or other methods. The problem is that there not any proven methods to achieve that and each lab analysis is costly :(.

Hi there
There are definitely strains with less than 0.2% total THC, it’s just that they will typically have <10% CBD content.
I’ve spent years trying to find product that is truly full THC compliant or close to it and only found a few strains.

Much of the time you’re really cherry picking CoA results to find something decent.

That said I wouldn’t bother with washing or anything - that’s crap.
A few practical tips:
Less trimming etc is generally better - if you ship biomass (flower plus leaves plus stems) that will usually be only 50% of the cannabinoid potency of the flower
Consider smalls and trim - smalls make great buying and will be lower THC - if the flower is borderline the smalls will probably be compliant.
CBG flower FTW - CBG is typically 50:1 to 100:1 CBG:THC and is often under 0.2%.
They’re out there: we’ve found a few CBD strains that are 10-15% CBDA and repeatedly tests from 0.15 to 0.3% and has always been under US total THC. The only problem is people tend to want the 20% CBD flower (which is typically 0.0 to 0.2% D9, but 0.5 to 1.0% Total THC. Fine for Switzerland but not Total THC compliant or <0.2% markets.

For these we mostly sell CBG or 1 or 2 strains we carry that are Total T compliant.

Either pick a market with more latitude (eg: Switzerland is 1% THC limit) or stick to CBG and lower potency strains that hit your threshhold (.2% or 0.3%)

I’ve attached a typical real compliant CBG flower CoA. (Not slanging - thus no product details)
Note the low non-zero value of THCA. All the THC in non-decarbed flower should be THCA, not THC, so vendors claiming “<0.3% D9!” are ignoring the fact that most top shelf THC flower also has <0.3% D9.

In general seeing a value for THCA here rather than zero is more trustworthy - when you see zero THCA on flower it usually indicates a low test sensitivity.
The sensitivity here is 0.04% - this is a reasonable figure for compliance testing. Some labs/CoAs will only show LOD or LOQ of 0.2% or something ridiculous.

Remember also these results are always just for 1 bud or another sample. They are rarely representative of that ounce, or that lb, or that tonne of flower. Thus repeat testing is advised to be sure.

Attachments: Hand trimmed CBG flower and flower for reference.

What’s the current THC level in your product?

The best bet would be to blend it with a compliant product such as hemp leaf or kief or some other filler - then use it for pre-rolls or capsules or something

Also look making moon rocks by dusting with CBD and terpenes or something.
These are all ways to recover lower quality flower while dropping potency, but not be worth the effort.


Fwiw if it helps for his next crop, I have found that growing either hydroponically, or in containers will reduce thc drastically. Mine tested nd. But it reduces cbd percentage by 40 to 50 percent. My 16% strain in the ground was 8% in hydro. It was .6 total thc in the ground.

Nice, thank you for the answer! Very interesting observation! The climate of my coutry -especially the microclimate in the area my friend is growing - is promoting THC concentrations >0,2% THC. For financial reasons -in order to make it worth it - he grows in his fields outdoors. Nice tip in any case!

1 Like

Thank you very much for the detailed response, you rock man! Yeah makes sense that the THC content in the case of 0,2% THC strains will be under 10%. I mean, usually the ratio of CBD to THC is 30:1 at best,the 100:1 ratio between these 2 for now is an exception and not the rule (?) - I have seen many cbd flowers advertised as 0,2% THC-20% CBD like it’s something natural. Woah, really interesting what you mention about CBG though!
Very nice tips about sending biomass - i’m wondering if the concentrations of terpenes would be 50% less too in that case - propably it would be or even more.
We can only sell the buds in our country (Greece) - not other countries. We wish we could just export the 0,6% THC buds in other countries where it’s legal but that is not the case. If they find out it’s 0,6 they confiscate and destroy it without any compensation. How fair is that?
Man, that CBG flower looks like the bomb! WTF, seriously!! If I’m allowed to ask and it’s not a trade secret, what is the strain? Wonderful!
We are not allowed to do moon rocks, we are not allowed to do extractions of any kind here. We can just sell the flower as is if it’s <0,2% THC or sell it to companies who make cbd oil and then buy the oil from them.
The THC content of the product of my friend is 0,6% - CBD is 13%.