How to Make RSO at Home Safely: FECO vs RSO and How to Dose It

How to Make RSO at Home Safely: FECO vs RSO and How to Dose It

Rick Simpson Oil is the strongest edible product most home cooks will ever handle. It's a thick, tar-dark, whole-plant extract made by washing decarboxylated cannabis in high-proof alcohol, then evaporating the alcohol off until only concentrated oil remains. Finished RSO commonly tests between 60 and 80 percent THC, which means a single grain of rice worth of oil — about 0.05 grams — can carry 30 to 40mg of THC. That is six to sixteen times a sensible first-time edible dose of 2.5 to 5mg.

That potency is why this guide leads with safety instead of technique. Making RSO means working around flammable ethanol vapor, and dosing it means portioning something where the difference between a pleasant evening and a lost day is half a grain of rice. Both problems are manageable at home, but neither forgives improvisation. If you have never made an infusion before, start with cannabutter and come back later. This is a graduate-level project.

The Non-Negotiable Safety Rules

If you can't meet every one of these, don't make RSO.

• Food-grade, high-proof ethanol only. Everclear or a comparable drinkable grain alcohol, the higher the proof the better. Never isopropyl (rubbing) alcohol, never denatured alcohol, and never naphtha — the petroleum solvent from Rick Simpson's original instructions. Isopropyl and denatured alcohol leave residues you should not eat. If high-proof grain alcohol isn't legally sold where you live, make a tincture instead.
• No open flames or gas stoves. Ethanol vapor is heavier than air and ignites easily. Evaporate with a double boiler on an induction burner, or a rice cooker run outdoors. Nothing with a pilot light anywhere in the room.
• Ventilate aggressively. Outdoors is best. Indoors, open windows on two sides and aim a fan so vapor moves away from you.
• Never leave it unattended. Not for a phone call, not for "just a minute." Evaporation is the step where fires start.
• 21+ only, and label everything. Finished RSO looks unremarkable and hits harder than anything else in your kitchen.

RSO vs FECO: Same Family, Different Wash

The two terms get used interchangeably, and the products are close cousins — both are whole-plant ethanol extracts. The practical difference is temperature. FECO, or full extract cannabis oil, usually means a cold wash: flower and alcohol both frozen before a brief soak, which pulls cannabinoids out while leaving most of the chlorophyll and plant wax behind. RSO is the older name, tied to Rick Simpson's protocol of long, room-temperature naphtha soaks.

The modern home method is FECO in everything but name: frozen materials, food-grade ethanol, a quick wash. Make it that way regardless of what you call it. You get a cleaner-tasting oil and you skip every problem the original solvent caused.

Step 1: Decarb First

Raw flower is mostly THCA, which does very little when eaten. Decarb before you wash: 240°F for 40 minutes in the oven converts about 90 percent of the potential THC, and sous vide at 203°F for 90 minutes reaches about 95 percent. The decarboxylation guide covers each method, and the decarb calculator handles the numbers. Decarbing first matters more here than it does with butter, because you can't casually re-heat finished RSO to fix a lazy decarb.

Step 2: Freeze, Wash Fast, Strain Fine

Seal the decarbed flower in a mason jar and freeze it overnight, with the ethanol in the freezer beside it (it won't freeze solid). Then work quickly: pour alcohol over the flower until it's covered and shake or stir for about 3 minutes — no longer. A short, cold wash captures most of the cannabinoids while minimizing the chlorophyll that makes extracts taste like lawn clippings. Strain through fine mesh, then again through a coffee filter, and press the plant material dry.

Step 3: Evaporate Low and Slow

Pour the strained wash into a double boiler over an induction burner, or a rice cooker set up outside. Keep it warm, not boiling. You are removing alcohol, not cooking the extract. Stir occasionally as it reduces. When the bubbling stops and it thickens into dark tar, draw it into oral syringes while it's still warm enough to move.

The Math: A Worked Example

Say you wash 7 grams of 20% THC flower that you oven-decarbed. Using the standard formula — grams × THC% ÷ 100 × 1000 × decarb efficiency:

7 × 20 ÷ 100 × 1000 × 0.90 = 1,260mg of THC available in the wash.

Seven grams of flower typically yields 1.2 to 1.4 grams of finished oil, and a quick wash plus two strains won't capture every milligram, so real-world potency usually lands in that 60-80 percent window. Call it 70 percent: each gram of oil holds roughly 700mg of THC, a rice-grain portion (0.05g) about 35mg, and half a grain about 17mg. Run your own numbers through the dosage calculator before anyone eats anything.

How to Dose RSO

The standard advice is to start with half a grain of rice, swallowed directly or packed into a capsule. Notice that even that conservative dose is 15 to 20mg at typical potency — well above the 2.5-5mg starting range we recommend for edibles in general. If you're new to edibles, RSO is the wrong place to start. Either build experience with regular infusions first, or dilute a weighed amount of oil into coconut oil so you can portion true beginner doses.

Whatever the dose, wait a full 2 hours before even considering more. Oral RSO can take 45 minutes to 2 hours to arrive and lasts longer than most people expect. Keep the dosing cheat sheet handy until you know your batch.

Storage and a Word on Medical Claims

Store RSO in labeled oral syringes — estimated potency, date, big letters — somewhere cool, dark, and locked away from kids, guests, and pets. Keep it secret, keep it safe.

One honest note to close on: RSO carries a lot of medical folklore, including claims that it cures cancer. The folklore exceeds the evidence. This is a cooking and dosing guide, not medical advice, and anyone considering cannabis for a health condition should have that conversation with a doctor.

FAQ

Can I use isopropyl or denatured alcohol to make RSO?
No, and this is the one rule with zero flexibility. Isopropyl and denatured alcohols leave toxic residues that don't fully evaporate, and naphtha is a petroleum solvent. Only food-grade, high-proof drinkable ethanol like Everclear belongs in anything you plan to eat.

What's the difference between RSO and FECO?
Mostly the wash. FECO usually means a cold, frozen, quick ethanol wash, while RSO is the older name tied to Rick Simpson's room-temperature naphtha method. The modern home version — frozen bud, food-grade ethanol, a 3-minute wash — is effectively FECO regardless of what's written on the syringe.

How much RSO should I take the first time?
Half a grain of rice or less, which still delivers roughly 15-20mg of THC at typical potency. If you're new to edibles entirely, don't start with RSO at all — dilute it into a carrier oil so you can portion 2.5-5mg, and always wait 2 hours before redosing.

Does RSO cure cancer?
There is no clinical evidence that it does. Rick Simpson's story made the claim famous, but folklore is not data, and nothing in this guide is medical advice. Anyone considering cannabis alongside cancer treatment should talk with their oncologist.

How should I store RSO?
In oral syringes, clearly labeled with estimated potency and date, kept cool and dark. Stored that way it stays stable for many months. Because it looks like a harmless dark paste, keep it locked away from anyone under 21.