Estimated Brewing Time:
Pewter Cauldron: 3 hours, 43 minutes and 30 seconds
Brass Cauldron: 3 hours, 21 minutes and 9 seconds
Copper Cauldron: 3 hours, 1 minute and 2.1 seconds

Ingredients:
500 mL of water
5 freshly cut Devil’s Snare tendrils1
50 g of Grindylow bones1
20 g of cornstarch2
40 mL of baneberry extract2
15 mL of helium gas, contained in a sea bass swim bladder2
2 standard measures of powdered bat wings2
1 clear quartz3

Instructions

Part One:
1. Add 500 mL of water to your cauldron.
2. Bring the heat to 393 Kelvin (119.85°C/247.73°F).
3. Add 3 freshly cut Devil’s Snare tendrils to your cauldron, then stir its contents once counterclockwise.
4. Add the sea bass swim bladder to your cauldron, slice it open with the Severing Charm, then stir its contents twice counterclockwise.
(Note: You should hear a deep rumble emanate from the potion while you stir. If you do not, quickly dispose of the potion and restart the process.)
5. Dilute 10 g of cornstarch in 20 mL of baneberry extract, mixing both ingredients vigorously until the mixture begins to froth.
6. Add your cornstarch dilution to your cauldron, then stir its contents three times clockwise.
7. Bring the heat to 417 Kelvin (143.85°C/290.93°F) and let the potion simmer in your pewter cauldron for 3 hours and 21 minutes.
(This would be 3 hours and 54 seconds in a brass cauldron and 2 hours, 42 minutes and 48.6 seconds in a copper cauldron.)

At this point, your potion should have a coral color and faintly smell of roasted almonds. Furthermore, you should begin to see some tendrils jutting from your cauldron’s shadow throughout the simmering stage of the process.

Part Two:
1. Stir the contents of your cauldron once counterclockwise, then once clockwise.
2. Turn off the fire and cool down your cauldron to 283 Kelvin (9.85°C/49.73°F) with the use of a Chilling Charm.
3. Sprinkle 1 standard measure of powdered bat wings on the surface of your cauldron, then stir its contents twice counterclockwise.
4. Turn on the fire and bring the heat to 365 Kelvin (91.85°C/197.33°F).
5. In a mortar, grind 2 freshly cut Devil’s Snare tendrils into a smooth paste, then add 20 mL of baneberry extract to the mortar.
6. Stir the contents of your mortar twice clockwise, then add them to your cauldron.
7. Sprinkle 1 standard measure of powdered bat wings and 10 g of cornstarch on the surface of your cauldron, then stir its contents three times clockwise.
8. Bring the heat to 700 Kelvin (426.85°C/800.33°F) and let the potion simmer in your pewter cauldron for 22 minutes and 30 seconds. In the meantime, place 50 g of Grindylow bones over the cauldron’s flame in order to char the ingredient.
(This would be 20 minutes and 15 seconds in a brass cauldron and 18 minutes and 13.5 seconds in a copper cauldron.)

At this point, the liquid part of your potion should have a fuchsia color but have no smell. A dark yellow gas should be produced from the surface of the remaining liquid - touching the gas will make it latch onto your finger until physically pulled away.

Part Three:
1. Bring the heat to 354 Kelvin (80.85°C/177.53°F).
2. Add the 50 g of charred Grindylow bones to your cauldron, then stir the potion four times clockwise.
3. Quickly drop the clear quartz into your cauldron and lean away from the potion. The liquid should immediately disappear in a hot explosion, leaving only a transparent gaseous fraction of your brew behind.
4. Immediately bottle the Garrotting Gas through the use of the Siphoning Charm.

Storage:

Keep your vial of Garrotting Gas in a cool and dark place, as exposure to sunlight may trigger the properties of the gas and increase the pressure inside the vial, causing it to explode. Garrotting Gas lasts for two months before expiring.

Usage:

In order to safely use a vial of Garrotting Gas, either throw a breakable container at the desired area or open the vial from a distance by using a Levitation Charm. Since Garrotting Gas is slightly denser than atmospheric air, it does not easily disperse upon being released.

Caution:

Do not remain close to areas where Garrotting Gas has been released, particularly if they are close to the ground. Garrotting Gas tends to accumulate owing to its higher density, but it still may be carried away by gusts of wind or walking passersby.