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Thread: Electric Blanket

  1. #1

    Electric Blanket

    My shop is an unheated garage. Right now the temperature is 30 degrees, in another month I will be lucky to see 20 degrees. So when I glue small projects I bring them in the house. Forget about big ones. I was thinking of covering big projects with an electric blanket during the drying process. Has anybody done that, and if so was it doable and how were the results?

    Thanks, DKT

  2. #2
    Join Date
    Nov 2012
    Location
    Wapakoneta, OH
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    611
    I'll use one with my vacuum press. Generally I'll use urea formaldehyde glue in that press, which takes a really long time to cure. So overnight with an electric blanket is the approach. I'll usually put another blanket on top of that to help hold the warmth in. Works really well, but I've also used brooder lamps (heat lamps for chicks) and a small electric heater set on low. They all work well, but I'm not sure my shop ever would get down to 20, typically without the heat on it would stay in the upper 30's.

  3. #3
    Join Date
    May 2010
    Location
    Orland Park, Illinois, USA
    Posts
    278
    Dietrich, I used one very successfully on some bent wood laminations for chair backs. Chicago area in Dec/Jan has the same temp issues as you are having. Needed to get the glue over 70F if it is to cure properly and need for 12 hrs. Wrapped my bending press in the blanket, used wax paper to keep the glue off the blanket. Then put an additional blanket and sleeping bag over the top. Temp was in the 90's inside per my thermometer. Some pics of the assembly
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  4. #4
    Join Date
    Jul 2009
    Location
    Amherst, New Hampshire
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    10,604
    Sounds like a great idea !!
    Faith, Hope & Charity

  5. #5
    Join Date
    Nov 2006
    Location
    Villa Park, CA
    Posts
    1,407
    Yep, I use an electric blanket when gluing up veneer in a vacuum bag (with urea formaldehyde glue). I put it on high and leave it all night. Works fine.

    I picked up the blanket on CL from someone who was closing out an estate. The blanket was almost new.

    Mike
    Ancora imparo
    Go into the world and do well. But more importantly, go into the world and do good.

  6. #6
    Join Date
    Dec 2006
    Location
    Floydada, Tx
    Posts
    1,941
    I used to use 6 mill plastic and make a tent and place a heat lamp in there. This will keep it above 60 depending on the weather.

  7. #7
    I think the strategy of covering the project with blankets or sleeping bags and using light bulbs to heat would work very well. I used to make longbows, even in the winter. And believe me when I tell you that winter in North Dakota is pretty much colder than most places. I made a box insulated on the outside with 1" styrofoam rigid insulation and put a half dozen 100 watt light bulbs inside. It was able to cure the epoxy glued bow blanks at 200F for many hours at a time, even when the temp in the garage was 0 F or less and the outside temp was -20 or -30F. I would glue up big and complex projects go inside the house, because glue itself needs to stay at temps above 50F to flow properly.

  8. #8
    Join Date
    Nov 2006
    Location
    Austin, Texas
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    1,448
    Beware of using an electric blanket outdoors or equivalent (such as a very cold shop). My son's neighbors put an electric blanket in an outdoor dog house on their back porch, and burned their house down.

    The thermostat in an electric blanket works by a small heater in the control to warm the control roughly proportional to the heat provided by the blanket. So if the room is 60 degrees, the little heater (often a pilot light bulb) warms the thermostat and cycles the blanket on and off. But if the room is 30 degrees, the heater never gets the thermostat up to shut-off temperature, and the blanket stays on continuously. With any folds in the blanket, it overheats - enough to set a house on fire. Seems crazy, but I watched the home being gutted and rebuilt.
    Charlie Plesums, Austin Texas
    (Retired early to become a custom furnituremaker)
    Lots of my free advice at www.solowoodworker.com

  9. #9
    My wife told me to thank you for your reply, Charlie Plesums. She has been against my idea for the reasons you cited. It makes sense to me also. So now I can bring my large projects into the den overnight until the glue sets up.

    Thank You, DKT

  10. #10
    Join Date
    Nov 2006
    Location
    Villa Park, CA
    Posts
    1,407
    Quote Originally Posted by Charlie Plesums View Post
    Beware of using an electric blanket outdoors or equivalent (such as a very cold shop). My son's neighbors put an electric blanket in an outdoor dog house on their back porch, and burned their house down.

    The thermostat in an electric blanket works by a small heater in the control to warm the control roughly proportional to the heat provided by the blanket. So if the room is 60 degrees, the little heater (often a pilot light bulb) warms the thermostat and cycles the blanket on and off. But if the room is 30 degrees, the heater never gets the thermostat up to shut-off temperature, and the blanket stays on continuously. With any folds in the blanket, it overheats - enough to set a house on fire. Seems crazy, but I watched the home being gutted and rebuilt.
    I had never heard about a thermostatic control working that way so I went on the web to see how electric blanket thermostats work. Best I can tell, the newer electric blankets (the article said 10 years back and newer) will not overheat, even if you bunch the electric blanket up, or do anything else to it. My guess is that there are sensors in the electric blanket that sense the temperature and give feedback to the control unit.

    Building a thermostatic control the way Charlie describes it seems destine for failure. People could put the electric blanket under other blankets (there are some that are bed pads now and are under everything), so the temperature of the blanket would be significantly different from the temperature of the control. Additionally, some people like to sleep in a very cold room so the thermostat would work very differently in that situation than in a 60 degree room. Finally, I have difficult believing that UL would approve such a thermostatic control. If they can cause a fire, under almost any conditions, the unit will fail.

    Mike
    Last edited by Mike Henderson; 11-16-2012 at 08:51 PM.
    Ancora imparo
    Go into the world and do well. But more importantly, go into the world and do good.

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