There is a lot of info on the internet about cold brewing coffee
(most related to making it for iced coffee or to have an acid-reduced cup of coffee),
so after reading and video-watching,
I've come up with a process that works for me.
My goal was to stop buying instant coffee
(since I couldn't find a fair trade version
without a lot of packaging)
to use in my morning milk/coffee/chocolate drink.
Because I need something concentrated,
I turned to cold brewing.
And because I didn't want to a) invest in more equipment (grinder, special cold brewers, filters, carafes), b) produce something in great volume (I only need it for my breakfast), or c) end up with stuff I had to throw away (like cheesecloth) rather than compost, I started with ground coffee and equipment I already have on hand.
The grind of the coffee should be suitable for a drip coffee maker, not a fine grind used in an espresso maker. From what I've read, the finer grind produces too much bitterness in the cold brew process. And if you're using a Toddy (a brewer specifically for cold brewing), you must use a coarser grind (like for a French Press) or it will clog their filter.
Weigh 4 oz. ground coffee into a container.
Add 2 1/4 cups (18 fluid oz) filtered water and stir to fully mix.
Cover and store in the refrigerator 12 to 15 hours.
Spoon into a coffee filter set into a funnel over a container...
and let drain 15-30 minutes.
At the end of the draining time,
press the grounds with the back of a spoon
to extract as much of the coffee concentrate as possible.
(Then the paper filter and used grounds can be composted
with your other kitchen scraps.)
Store concentrate, covered, in the refrigerator
for up to 2 to 3 weeks.
I use an old salad dressing jar -
it's glass and the right size.
I found 3 Tbsp or 1 1/2 fluid oz. of concentrate to about 8 oz. of skim milk gives me a similar flavor to the tablespoon of instant coffee I had been using. However, everything I read suggested a more generous ratio of 1 part concentrate to 3 parts water or milk (hot or cold, depending on what you are making).
These measurements make about 24 Tbsp of concentrate which lasts me for 8 days.
It's definitely more expensive than the premium brand of French Roast instant I've been using - about 25% more. And a pound of ground coffee doesn’t produce as many cups of cold brewed coffee as hot brewed, so I wouldn’t use this process to make hot coffee for a crowd. But for now it’s my best option to have fair trade coffee in a concentrated form.
The best video info I found here which I adapted for my needs.