Making a Freezer Mug
Most recent answer: 07/04/2013
- Jim (age 16)
Sequim WA USA
A salt solution should work. So should an ethanol solution. Either way, remember that for these solutions there isn't a single sharp freezing point. The freezing point for the whole solution is the temperature where freezing starts or melting ends. At lower temperatures, the solution becomes more concentrated, lowering the freezing temperature, until the solution becomes as concentrated as it can get, "saturated". So for a solution of NaCl the lowest freezing temperature will be about -21°C even for a small amount of salt.
On materials:
Copper usually isn't used in direct contact with food because it can slightly dissolve and give off-flavors. Aluminum conducts heat almost as well and forms a hard oxide coating which protects it. Maybe you could start with a standard aluminum can.
You may need a small hole in the jacket to prevent large stresses when the water expands as it freezes. So salt water may work better than an ethanol solution, because the salt won't gradually evaporate, unlike ethanol. It'll be easy to top up the water occasionally.
How do you plan to seal the outer insulator to the inner conductor? Repeated thermal cycling may be hard on most glues. Some, such as epoxies, are toxic. You should check what materials are used in food-grade containers. Perhaps some sort of silicon rubber would work. I think this sealing problem will be your biggest difficulty.
I wonder if it might work best to make both the inner and outer cans out of aluminum, and just use some spacers in between for stability. This would freeze a little more quckly for faster re-use. Then you could use a removable foam insulating sleeve when it's out of the feezer.
Mike W.
(published on 07/04/2013)
Follow-Up #1: freezer mug
- Jim (age 16)
Sequim, WA, USA
Let us know how this works out. It just might catch on.
Mike W.
(published on 07/06/2013)
Follow-Up #2: cooling mugs
- Casey (age 27)
Los Angeles, ca
I think you've put your finger on the biggest problem- spillage. Having recently lost a computer screen to a water spill, I'm sensitive to that issue. Some sort of silicone rubber seal should be easy to include.
Mike W.
(published on 07/23/2016)