How to decarb weed (and why THCA needs heat)

What does decarbing weed mean?

Decarboxylation, or decarbing, is the chemical step that turns THCA into THC. Heat removes a small carboxyl group from the THCA molecule, it leaves as carbon dioxide, and what remains is THC, the compound that produces the high.

Smoking and vaping do this in a split second, because the flame or heating element is hot enough to convert THCA as you inhale. Edibles are different. Nothing in a mixing bowl gets hot enough, for long enough, unless you decarb on purpose first. That is the whole reason the step exists.

Why isn't raw weed intoxicating?

Because the plant doesn't make much THC. Fresh and dried flower is mostly THCA, which isn't considered intoxicating on its own. The THC shows up once heat has done its work. Our guide to THCA vs THC goes through the difference in detail, including why Canadian labels show "Total THC".

That's also why a lab report on raw flower can list a big THCA number and a small THC number. Total THC on a Canadian label adds the two together, using a weight adjustment, to show the most THC the product could produce once fully heated. It's a ceiling. Conversion is never perfectly complete in a kitchen.

What temperature and time does decarboxylation need?

There isn't one magic number. A 2016 study heated cannabis extracts in a vacuum oven at 80, 95, 110, 130 and 145 °C for up to 60 minutes. It found the reaction follows a predictable curve: the hotter it is, the faster THCA disappears. THCA also converts about twice as fast as CBDA and CBGA, the acid forms of CBD and CBG.

A separate 2016 paper from the European Industrial Hemp Association pooled earlier experiments and estimated roughly 3 hours at 100 °C and 4 hours at 98 °C for full conversion, with only about 10 minutes needed above 160 °C. The authors note that the studies used different methods, so the figures are rough.

The catch is that heat also destroys what you're trying to make. The same paper notes THC starts to evaporate from about 157 °C, and that THC can degrade into CBN, a different cannabinoid, at temperatures as low as 85 to 100 °C. Its summary of one older experiment had THC peak at 145 °C after 7 minutes and fall by half by 40 minutes. Decarbing is a window, not a race to the highest temperature.

How do you decarb weed in the oven?

The oven is the usual home method. No study has tested a specific home recipe for whole flower, so treat the steps below as a sensible starting point built on the lab ranges above. Oven dials are often off by several degrees, so a cheap oven thermometer is worth having.

1. Pick a temperature in the 100 to 130 °C range. Lower is gentler on the THC but takes longer, and the studies suggest anything below 100 °C needs hours. The lab data points to about 110 °C for roughly 30 minutes as an early marker, and many cooks choose longer than that for dried flower because plant material heats more slowly than a thin extract film.
2. Preheat the oven fully and check it with an oven thermometer before the cannabis goes in.
3. Break the flower into small, even pieces by hand. Don't grind it to powder, which can scorch. Smaller pieces heat more evenly.
4. Spread the pieces in a single thin layer on a baking sheet lined with parchment, and cover loosely with foil to hold in some of the aroma.
5. Bake for your chosen time, keeping an eye on the colour. Lightly toasted and golden to brown is expected; dark and crisp means it's been overheated.
6. Let it cool completely before you handle or store it, then use it in your recipe within a reasonable time. Decarbed flower is more fragile than raw.

Expect a strong smell while it bakes. Our guide to what weed smells like covers where that comes from. Sealed containers and ventilation help.

Decarbing also isn't a one-way trip to maximum potency. Because some THC is lost to evaporation and degradation along the way, and conversion is never perfect, the finished product will contain less THC than the label's Total THC suggests.

Is it legal to make weed edibles at home in Canada?

Yes, for adults, within limits. Health Canada's backgrounder on the Cannabis Act lists making legal cannabis-containing products at home, such as food and drinks, as something adults may do, as long as dangerous organic solvents aren't used. Solvents such as butane and other flammable hydrocarbons are banned because of the fire, explosion and health risks. Baking or cooking with decarbed flower doesn't use a solvent.

Provincial rules vary on the legal age and on where you can consume, so check yours. The federal public possession limit is 30 grams of dried cannabis or its equivalent. Our weed measurements guide explains how that limit is counted for other forms.

How strong will my homemade edibles be?

This is the part most guides gloss over. Licensed edibles are tested and labelled, and Health Canada's cap is 10 mg of THC per package. A homemade batch can't be checked the same way. How strong it is depends on the flower's Total THC, how much of the THCA converted, how much THC was lost to heat, and how evenly the cannabis was mixed through the recipe.

Unevenness is the real trap. A brownie from the corner of a pan can have a very different amount from one at the centre. Stir thoroughly, cut equal portions, and treat your first batch as unknown. If you're still waiting after an hour, resist taking more, since that is how people end up greening out. For what to expect afterward, see how long a high lasts.