Making a Keep-Warm Box

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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.

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    43 Discussions

    0
    KelleyB20
    KelleyB20

    Question 1 year ago on Step 6

    Excellent idea for more than glue and paints. Just wondering though, where are you buying your incandesent light bulbs now The CF type just don't put out any heat. Thanks

    0
    SparkyDon
    SparkyDon

    Answer 7 months ago

    You can get appliance bulbs and also “Rough Service” bulbs made for construction sites.

    0
    joebaby1953
    joebaby1953

    Answer 1 year ago

    I have been buying incandescent light bulbs at the local dollar store. If you have an Ocean State Job Lot near you, I also am still getting them there. I think next time I am there I will buy a lifetime supply. At my age that won't be that many. LOL

    0
    DonS89
    DonS89

    Answer 1 year ago

    Well, the 75 was left in the socket from when I was building my house but I don't use them for lighting anymore so I still have a dozen or more 60s from when I stocked up a few years back.

    0
    SparkyDon
    SparkyDon

    7 months ago

    I am taking your awesome idea to the next level Saturday morning. A neighbor was tossing a MiniFridge and I asked for it. All I need is the thermostat ran inline to the already installed bulb and I’m in business. Thanks for the solution.

    0
    JimH209
    JimH209

    10 months ago on Step 6

    If the light bulb was at the top of the box, wouldn't it be more efficient!
    I also wonder if a heat lamp bulb would work better with a thermostat ... 🤔🤔🤔

    1
    MichiganDave
    MichiganDave

    1 year ago

    I applaud your roadside beautification project.
    And I think I can do something similar to proof and rise my bread dough. Thanks.

    1
    accesswoodworx
    accesswoodworx

    1 year ago

    Great idea for thermal regulation. I just moved and have a shop separated from the main house, so I have been debating on what to do with all my resins, glues, and paints. If I can find a dead fridge I could probably use your same light bulb and thermostat idea to keep everything above freezing. Thanks for the idea.

    0
    DonS89
    DonS89

    Reply 1 year ago

    Thanks for your comment. If I were to do it over, I would probably use an aquarium thermostat and also include a small fan for more even heat distribution. Read some of the other comments for some great ideas.

    0
    mjenkins1
    mjenkins1

    1 year ago on Step 6

    Thank you for posting. I am losing expensive paint as we speak so this is well-timed. This will be my last year of frozen paint. Great, and useful project!

    0
    DonS89
    DonS89

    Reply 1 year ago

    Check out the comments below, there are different alternatives to the way I did it. Good luck and thanks for the comment.

    0
    DonS89
    DonS89

    Reply 1 year ago

    RalphM49, thank you! The inside is a little over 13" wide. Gotta love Dollar Tree!

    5
    sandalwood1
    sandalwood1

    1 year ago

    As wooden boat builders, my partner and I took a similar approach to keep epoxy warm (lower viscosity), and sandpaper crisp. We used cast-off refrigerators for the cabinets, on account of good insulation qualities, and tight door seals.

    0
    DonS89
    DonS89

    Reply 1 year ago

    I belong to a woodturners club and a lot of folks use old fridges for kilns for drying blanks. I didn't need that much capacity!

    0
    sandalwood1
    sandalwood1

    Reply 1 year ago

    Discarded dorm-size refrigerators are the answer to smaller capacity needs. They come in sizes down to 1.1 cu ft (18.7w X 17.8d X19.5h).

    1
    Prfesser
    Prfesser

    1 year ago

    Nice! I made something similar for curing epoxy-fiberglass parts, except that the panels you creatively acquired weren't available around here, at least not for free. I used 1/4" tile backerboard for the box, surrounded by 2" thick blueboard styrofoam, glued with epoxy, and with edges protected with Gorilla tape.

    Got a thermostat similar to this one on eBay, runs around $20-25:
    https://www.ebay.com/itm/AC-112-Pets-Digital-LED-T...
    or search for 'aquarium thermostat'. With a 60 watt bulb and a small fan to distribute the heat, an internal temperature of 150 F could be maintained against 45 F outdoor temperature.

    Also: check furniture store dumpsters, I was able to scavenge large pieces of 2" styro beadboard for another curing box.

    0
    charlessenf-gm
    charlessenf-gm

    Reply 1 year ago

    "...the panels you creatively acquired..."
    Gee, don't they have Elections where you are?? ;)
    What a great use for old Trump Signs - creating and maintaining hot air!

    0
    DonS89
    DonS89

    Reply 1 year ago

    When looking for signs, I was surprised to see that were NONE left on the streets - maybe they are catching on.

    0
    JohnW51
    JohnW51

    Reply 1 year ago

    Why would you need 150 F? About 40 F would be more than warm enough. The object is to just keep the items above freezing. I keep all my stuff in my attached garage at the opposite end from the door. I have a thermometer out there. I have never seen it get below about 40 degrees, but then I live in central Oklahoma where we normally don't have extended periods at extremely cold temperatures. Never have lost any paint or glue except when I didn't get a container completely sealed.