With the Meth Lab Cold Brew Coffee Method, you can brew 800ml of concentrated coffee from 12oz of grounds with minimal up-front cost and very low effort. The concentrate makes an 8oz iced coffee from 2oz of concentrate (more or less, depending on how you like it).

It's called the Meth Lab method because it looks... unprofessional. But the results are powerful and (relatively) addictive.

The Meth Lab Cold Brew Coffee Method balances low cost, high quality, and it's easy. I developed it while working on Co-op Bar #3 as a visiting artist at Sierra Nevada College's MFA summer residency. The Co-op Bar was designed because artists tend to hang out in bars and cafés, and a co-op structure allows them to capture the profits and redistribute them as artists grants. 12oz of Coffee grounds can cost around $8-12, and selling cups of cold brew at the Co-op Bar we were able to raise a significant amount of money.

Here's what you'll need...

Step 1: Gather Materials

Here's what I used. Consider these a starting point - you may find substitutions that will work just as well or better. I'll do my best to explain why I used what I used as we go along so your substitutions will be just as effective.

2) 2 liter glass jars (glass is easy to clean)
1500ml of clean drinking water
a one gallon plastic jug, cut in half as pictured
A large coffee filter - I happened to have 250 filters for a BUNN U3 Brewer I bought online for about $23. They work great, but you can use whatever works.
A push pin

Step 2: Add Ground Coffee

Pour 12oz of Ground Coffee into one of your jars. Regular grind is fine and buying pre-ground coffee in a 12oz bag from your supermarket will work. The brewing ratio is 1lb of coffee for every 2L of water, but we're going to scale it down to 12oz/1500ml.

Step 3: Puncture the Bottom of the Gallon Jug and Trickle in Water

Next we're going to trickle water into the jar of ground coffee. The reason to trickle it in slowly is that it gives the grounds time to absorb the water. If we were to pour all the water all in fast, there wouldn't be enough space in the jar and it would overflow.

Poke one hole in the bottom portion of the gallon jug. Put the hole at a low point, toward the center of the jug.

Add portions of the water, refilling as needed, and give it plenty of time.

Step 4: Pour in the Remaining Water and Wait

Not all the water will trickle in. When the trickle has stopped, slowly poor in the remaining water and close off the top.

Leave it, undisturbed, for around 10 hours. If you remember, at around 10 hours and every few hours after that, you can give the jar a shake. It's not critical.

Total brew time can be 12-24 hours, it doesn't make a huge difference.

Then you're ready to filter your cold brew!

Step 5: Filter Your Cold Brew

Place the funnel side of your gallon jug on top of your clean jar. The funnel shape is important, otherwise you wont get all the cold brew out of the grounds. In my experience, the funnel shape yielded 50% more cold brew.

Insert the filter into the jug/funnel

Pour your liquid and ground mixture into the filter. Scoop out all the grounds from the jar and get as much as you can into the filter.

Let it stand for several hours. You'll get to 500ml quickly, but given time you'll end up with 750-800ml of cold brew.

Step 6: Dillute and Drink Up

Mix the concentrate with ice and water. Again, 2oz of concentrate and 6oz of water is a good place to start, but you can do it to your taste. Beware, it's strong.

According to the Filtron folks, "the concentrate will keep for more than 6 weeks under refrigeration... just as delicious as the day it was made. The concentrate will last 4-5 weeks un-refrigerated (up to 75)" (I also own a Filtron and it's great)