Is there a way to determine the THC content of my "Green Dragon" mixture?

October 20, 2006 9:06 PM

I'm not a smoker, so I consume most of my THC by steeping 1/4 oz of weed in 26 oz of 151-proof rum. (After a week or so, I strain the rum and consume it about a tablespoon at a time. It suits my needs quite well.) I remember from my days of making homemade wine that there was a fairly easy way to estimate the alcohol content of wine by measuring the specific gravity before and after fermentation. Is there any similar method to get a ballpark idea of how much THC is in my rum?
posted by Tbola to science & nature (11 answers total)

No, unless you have ultra precise equipment. There are probably only a few grams per liter of THC in the solution, or less. Unlike an alcoholic drink which could be anywhere from 1-98% ethanol.

Also, there may be all sorts of other substances soaked into the solution from the marijuana, similarly affecting the weight.
posted by delmoi at 9:16 PM on October 20, 2006 [1 favorite]

As an ex-chemist, delmoi is correct. Your tincture contains a variety of compounds, including several cannabinoids besides THC, and many water-soluble compounds that are not psychoactive. The relative concentrations of these compounds varies depending on the weed. If you want to guesstimate, take a look at some numbers on weed potency - if your weed is "average" it is probably around 5-6% THC. That is maybe like a gram in your quarter ounce.
posted by nanojath at 10:29 PM on October 20, 2006

I doubt that any easy measurement would give you a better idea than what you'd get from a touch-test of the stickiness of the weed before you steep it.

Do you razz the mixture up in a blender before letting it settle and steep? Because I expect that doing so would tear open the resin glands and give the alcohol better access to the THC-laden resin therein.

Cooking oils are another excellent solvent for this kind of thing; better than rum, in that they don't load themselves up with water-soluble plant juices that are of no use to you.
posted by flabdablet at 12:13 AM on October 21, 2006

While i have nothing useful to add, i'd like to ask for more information regarding your THC intake method. Specifically, the amounts and processing, and most importantly, the effects as compared to more common methods such as smoking/vaporizing.
posted by CautionToTheWind at 3:28 AM on October 21, 2006

CautionToTheWind:
To expand on what I put in my question - in a large, clean mason jar, I throw in 1/4 oz. of weed (I've tried crushing the leaves first with mortar & pestle, but I found that released too much of a pungent "weedy" smell around my apartment, and my elderly landlords live right below me. So I play it safe.)
I then pour 26 oz. of 151 proof rum into the jar - seal it up, shake it a bit, and put it somewhere out of sight for about a week. (I've tried longer, but I haven't any noticeable increase in potency beyond this amount of steeping time.)
I usually give it a shake about once a day.

After the week is done, I pour the rum back into a clean 26 oz. bottle, using a coffee filter to remove the (now useless) vegetation. Using a liquor bottle is a good idea, because you can attach a pourer to it, and that's useful for more accurate measurements.

I generally mix one tablespoon of rum with a small amount of fruit juice, and just slug it back.
(Note at no time during this process is there any real tell-tale weedy smells being released, as there is with smoking, or cooking it into butter.)

Now here's the key: you have to wait longer to feel the effects. Often I feel it with 10-15 minutes, but sometimes it's more like 45 minutes before you're feeling the full impact of it.
(I only say this because some people decide way too early that they need more, and end up consuming to much... so be patient)
It's less of a "head" buzz and more of a body buzz than smoking gives.
Plus, I find that consuming it this way the effects last for about 3-4 hours... during which the high is pleasantly constant, and after which the high leaves very quickly and cleanly.

Hope this helps!
posted by Tbola at 6:28 AM on October 21, 2006 [7 favorites]

Okay, maybe I should forget about trying to get a "meaningful" measurement of THC... but would there be a way to get a "relative" measurement (or estimate), so I would be able to ascertain whether a batch is stronger or weaker than previous ones?

Again - if I remember the way alcohol is measured in wine making, you are actually measuring the amount of sugar used in the fermentation, and the alcohol % is deduced from that.
Would there be any similar methodology I could do to the rum (or the grass itself) before and after to get an idea of how much has transferred?
(sorry if I'm kinda repeating the question - I'm just trying to re-clarify a bit.)

(And could someone explain the "touch test" of the stickiness of weed?)
posted by Tbola at 6:37 AM on October 21, 2006

I also don't have any constructive comments; I just wanted to thank you for asking the question. I think I'm going to have some fun in about a week.
posted by i_am_a_Jedi at 7:32 AM on October 21, 2006

You've restated the question, so let me restate the answer.

The basic problem that gets in the way of an easy but meaningful measurement is the fact that the quantity of active ingredient relative to everything else that's in your mixture is very very small. Measuring alcohol content with a hygrometer is easy because (a) the specific gravity of alcohol is markedly different from that of water (b) in anything you'd bother measuring, there will be a substantial percentage of alcohol.

1/4 ounce of weed is about seven grams. If it's really really really good weed, you might get half a gram of resin out of that. Of that, maybe a few percent is THC. When you dilute that in 750ml of rum, you're just not going to see a specific gravity difference between batches even if one has ten times the active ingredient of the other.

What you actually need is a specific chemical test for THC. Luckily, the War On Drugs has made such things available fairly cheaply. You'll probably have to mess around a bit with preparing calibrated dilutions for testing, and you'll have to cross-check the test results against your own reactions before you can extract meaning from them, but at least there's some likelihood that you'll get a useful result this way.

Or you could just see how sticky your weed feels as you handle it (the "touch test").
posted by flabdablet at 7:34 AM on October 21, 2006

Tbola you tempt me greatly! I have eaten cake with THC and am aware of the different cicle it has when compared with smoking. I am a big fan of that but my cooking sucks so your method might just be the thing.
posted by CautionToTheWind at 8:46 AM on October 21, 2006

Flabdablet:
Thanks for clarification.
I had no idea that the actual quantity of THC being involved in my process was so minuscule. A chemical test sounds like the ticket.

CautionToTheWind & i_am_a_Jedi:
One further note - I've noticed that if my "steeping" is done in a cool place (like a cold storage room), it tends to take longer.
So average room temperature is what I'm basing the 1 week number on.
It is possible to speed up the process by heating the solution, but then you have to deal with "the smell", and more importantly - potentially losing precious THC-absorbing alcohol to evaporation.
posted by Tbola at 9:05 AM on October 21, 2006

The alcohol could screw up the test, plus I don't know if that specific test can be reused, and it also looks for metabolites of THC (what your body turns THC into).
posted by delmoi at 7:51 PM on October 21, 2006