What can I do to improve this cold-brew method? The cold-brewed coffee we made was weak and tasteless. I spent an hour with the roaster to get the grind right but here are the steps and process:


Purchased coffee, and requested that they be ground to "drip grind" coarseness
4 to 1 by volume (measuring cup) room temperature water to coffee grounds
Stirred in the jar then refrigerated for 24 hours
Poured it manually through a paper filter


Result: as I was pouring the coffee through the water filter, I could tell that the coffee looked kind of translucent. The taste was weak and bland. There was no complexity, and while it was not bitter, it was very bland. 

So here is the paradox that perplexes me.  I'm pretty sure that the grind is still too fine, but then on the other hand the coffee seems to be in on the weak side.  The brew process is somewhat simple, but "immersion" is a standard acceptable cold brew process. 

What do you think we did wrong? Let's assume that the beans were of decent quality.
The problem is probably temperature of the water when steeping. For a better, more full-bodied result, steep at room temperature. Seattle Coffee Gear, for example, did a test of cold-brewing in the refrigerator and at room temperature, and reported that the room-temperature-steeped cold-brew was tastier, stronger, and more full-bodied. See also this question for more.

In sum, don't refrigerate it until it's done brewing. Your fridge slows the extraction process down.