BLAST FREEZER

Baby it's cold inside

I was on a job and the director asked me to find a blast freezer to super chill some drinks in a hurry.

I had never heard of this device so I did some research and found that:

a. Blast freezers are incredibly expensive to buy

b. The company that rents all of the kitchen equipment to tv commercial productions doesn't own one, probably because of a.

So I decided to make one.

I went to the home center and bought a cheap awning window (like in a basement) and a couple of sheets of 2" foam insulation, as well as some foam panel adhesive in caulking gun tubes.

I cut a piece of plywood the size of the window plus 4", then cut a hole in the plywood to fit the window opening, like this:

I screwed the plywood to the window, then constructed a box out of the foam, as you can see, consisting of a top,bottom, two sides and a back. I made my box 10" deep. I cut the foam with a handsaw and glued it all together with the foamboard adhesive, using 3" drywall screws to hold everything together while the adhesive set up.

Using a 4" hole saw, I made a hole in the center of the top and bottom, and then placed a foam baffle over each hole, supporting it on little foam blocks, like this:

You can see the 3" screws I put in two corners to keep this together while the adhesive set up

I had a 4" blower lying around, so I used it to circulate the air in the freezer. I ran an elbow out of the hole in the bottom and used a small length of flexible duct to connect it to the intake of the blower .

bottom view

Then I used another piece of the duct to connect the output of the blower to the "ice tunnel" which I glued on top of the freezer box.    This  is simply a foam box

 with a removable lid which connects the output of the blower to the 4" hole in the top of the freezer.

The ice tunnel, lid removed. Dry ice arranged in tunnel fashion also

lid taped on

I also put a cookie cooling rack shelf in, supported by foam blocks glued to the side walls, and some battery powered LED lights:

In operation, I simply filled the ice tunnel with dry ice and turned on the blower. The blower sucks the air from the bottom of the box and sends it through the ice tunnel and back into the box through the top hole. So the air should get colder and colder as it is recirculated. And it does. The temperature dropped amazingly quickly and bottomed out at about minus 44 degrees Fahrenheit:

Check out the minus sign on the left. The flexible aluminum ducting behind the thermometer is covered with frost.

Whatever I put in the freezer got cold pretty quickly, so it seems to work. Of course we never used it for the job, but now I know how to make one, and so do you.