Introduction: Making a Keep-Warm Box

About: Just an old guy who likes to dabble in an eclectic mix of technologies and arts.

Last year during a cold spell - below 32 degrees F for 5 days straight - I lost about $100 worth of glue and latex/acrylic paint due to freezing. I have a 10' x 16' uninsulated shed that I call my shop. When I want to work in there in the cold days I have a propane-top heater that does very nicely but I can't run it 24/7.

The proposed solution I came up with was to make a small insulated box with a light bulb for heat to prevent these reasonably expensive liquids from freezing.

This is how I did it.

Be sure and check the pictures for notes.

Step 1: Gathering Materials

Material List:

  • Light Fixture with 75 watt incandescent bulb
  • 2 pcs of old Appliance Cord
  • Female Electrical Plug
  • Thermostat
  • Insulation
  • Bits and Pieces of Wood
  • Hinges
  • Glue - PVA and CA
  • Brads
  • Staples
  • Odd screws
  • Instant Reading Thermometer

I had everything except the Thermostat and Insulation. In my junk collection, I had several thermostats but most wouldn't handle 120 volts. I also had a water heater thermostat but testing showed that I couldn't get it to shut off until the temperature reached 112 degrees so that was out also. I found a Heating Tape Thermostat (2nd picture) that turns on at 38 degrees and off at 50 degrees. It is rated at 120 volts and 15 amps - way more robust than I need. The cost was $12.

For Insulation, I had thought to use a sheet of foam insulation, the cost would have been $14. But one day as I was doing errands I noticed quite a few of these signs (picture 3) along the road. I consider these signs unattractive and a distraction but they are someone's property. However if you look closely, they all say "Deadline Dec 15th". This was December 18th so obviously the signs were abandoned property and therefore available. In the interests of public safety and roadside cleanup I promptly removed 16 of them in a 2 mile stretch.

These signs are made of plastic in a honeycomb structure - perfect for insulation. In fact they are superior to foam insulation according to scientific reports on the web.

Be sure and check the pictures for notes.

Step 2: Tool List

Tools I used:

  • Tape Measure
  • Table Saw
  • Miter Saw
  • Brad Gun
  • Retractable Knife
  • Straight Edge
  • Drill Press
  • Screw driver
  • Wire Cutters
  • Wire Strippers

CAUTION: Some of the above power tools can cause serious injuries. Please use all proper safety procedures.

Be sure and check the pictures for notes.

Step 3: Making the Frame

I decided to make all elements of the frame 1/2" thick by 1 1/2" wide. So I ripped 8 pieces for the legs and 16 pieces for the top and bottom frames and four pieces for the door frame.

The leg pieces were assembled into L pieces using wood glue and brads and the frame pieces were all mitered and glued and bradded at the corners.

Finally, the top and bottom frames were fitted to the tops and bottoms of legs and glued and bradded together.

Be sure and check the pictures for notes.

Step 4: Assembling the Box

Using a retractable knife and straightedge, the cladding and assembly was quickly done. The outside skin was glued with Super Glue and stapled to the frame. Multiple layers were achieved by cutting to fit inside the frame and box, adding a little Super Glue and pressing each piece into place. Final thickness is about 1" all around.

The door was similarly clad and hinges were attached.

I then took it outside and applied a coat of paint from an old used rattlecan.

Step 5: Finishing Touches

I stuck the thermometer through the skin to just above the thermostat position.

I made a simple wooden bracket with a removable screw to hold the door closed. Pressing on the door relieves pressure on the screw then just pull it out to open the door.

I assembled the light socket to a piece of wood and attached a short length of old appliance cord. The other old appliance cord was pushed through the skin, the female plug attached and the thermostat was plugged in. Then the light was plugged into the thermostat.

The last two pictures show some glues and paints stacked in the box. Note that they are arranged to shield the thermostat from direct view of the bulb. This is to prevent rapid cycling of the light and allowing the air in the box to heat up better.

Be sure and check the pictures for notes.

Step 6: Success and Future Plans

In this last picture, the temperature in the shed is 30 degrees while the light bulb is holding the temperature at 48 degrees (measured at the thermostat)

I'm thinking that installing slatted open-air shelves would increase the capacity of the Warming Box and then I would devise a shield so the heat from the bulb is directed upward.

If you got this far, thank you for reading about my simple creations. All comments and questions will get a response.

Go and make something.