How does the insulation actually work to keep it cold for 24 hours?
asobu uses copper double-walled vacuum insulation in the stainless steel carafe and rates it to keep cold brew cold for up to 24 hours. The copper layer is the detail that sets it apart from a plain vacuum flask. asobu also says the concentrate can be enjoyed hot or iced.
What material is the reusable filter made from?
A reusable stainless steel mesh that is easy to clean. Use coarse grounds: with them it tends not to clog at all, and fine grounds are the likely culprit when it does.
How does it stay leakproof?
asobu calls it 100 percent leak-proof and spill proof. Two small parts do the sealing: the gaskets, which should not be overtightened, and a ball bearing in the valve that has to sit in place for a proper seal. Look after both and it does not leak or spill.
Is the brewing carafe BPA-free?
Yes. asobu makes the brewing carafe from clear Tritan, which it describes as BPA-free, food-grade and non-breakable. The carafe you carry and drink from is insulated stainless steel.
Is it actually good for camping or backpacking?
asobu recommends it for backpacking, boating, camping, fishing, hiking and travel, and calls it leak-proof. It weighs 2.5 pounds and stands 14 inches tall, so it suits a pack or a car rather than a pocket. A batch needs to steep for 12 to 24 hours, so start it the night before you leave.
Are there any real downsides?
It does well on every count that matters. The downsides are practical: a batch takes 12 to 24 hours, so you are always making tomorrow's coffee today; the brewing chamber holds 32 ounces, and one owner wishes it were larger; and the small sealing parts, the gaskets and a ball bearing in the valve, need care when you wash them.
