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Incandescent light bulb heating for drying paint at low temps...

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  • Incandescent light bulb heating for drying paint at low temps...

    Couple months ago would have been perfect for drying paint, hovering around 90° for a month or two. Now (unheated garage/shop), I'm looking at low 30s during the night with highs in the low 50s for the day.

    I'm still happy with the Rustoleum Hammered that went on the lathe, it's held up pretty well for me so far, so decided to go that route for this project too. Home Depot mixed 3 different hammered colors making a gallon of some nice smoky silver/gray for this project, but for brushing on, this is what they recommend temp wise:

    Apply only when air and surface temperatures are
    between 60-90°F (15-32°C) and humidity is below 85% to
    ensure proper drying. Do not apply to surfaces that will
    exceed 200°F (93°C). Do not use on galvanized steel.
    This is the project with furring strips behind it:

    ...plan is to quickly make a 3 sided hinged (wire hinges) tent with the furring strips, then wrap the frames with heavy mil painters drop cloth. Drape another length to cover the top and make a tape shut front door. Then run a 60 - 100 watt incandescent inside the column with maybe a couple more lights on each side, towards the bottom (heat rising?). If I need to, guess I could run a timed fan (1 hour on/1 hour off) to vent?

    So the question... how many bulbs @ what wattage to heat the local area enough for good paint drying in temps that will not be ideal? Anyone have success doing something similar?

    Last edited by caveBob; 11-10-2014, 10:00 AM. Reason: details...

  • #2
    Why not get a small 110 volt heater (they don't cost much) and put that under the tent, it doesn't have to be set on high, just enough to keep it warm.
    The shortest distance between two points is a circle of infinite diameter.

    Bluewater Model Engineering Society at


    • #3
      Infra red patio heater?


      • #4
        How draughty/drafty is is the work space ?

        My vote is that a single 100W bulb placed within the column at
        the machine base and illuminated for at least two or more hours
        will produce a prominent rise in overall surface temp of the casting
        in still air with ambient conditions of 50F without insulative wrap.

        It is easy enough to do a trial run.

        For safety, be mindful of localized solvent/paint fume build-up within
        an anti-draft wrap or within the entire work area. A broken bulb, a
        pilot light, a fan motor, cigarette, static or other ignition source might
        lead to mishap. Respiratory protection against organic vapours might
        be advisable, too.

        A couple of alternatives to radient heat from bulbs that might be worthy
        substitutes are conductive sources like magnetically-attached external
        block heaters and battery warming blankets. Another possiblity is a
        portable/countertop single element warmer.



        • #5
          I'd use a heat bulb like they use to keep food hot.
          "Let me recommend the best medicine in the
          world: a long journey, at a mild season, through a pleasant
          country, in easy stages."
          ~ James Madison


          • #6
            I feel either way would work, leave a small opening at the top for ventilation. as long as you keep ambient air from the column it will remain warm with a 60-100w bulb. Start with a lower wattage bulb, Too hot can mess with some types of paint leading to wrinkles, cracks or adhesion problems.
            A dimmer could help fine tune temps.

            Build your tent, set up a light over night and check the surface temps before you paint. Or paint a test panel, slip it inside the tent on the column and check results.

            My small part drying oven was an old metal kitchen cabinet, used two lights on separate switches with a dimmer on one, only needed one with two x 100 watt, (use dimmer below 100watts, light + dimmer light for 100+.) I found that I preferred painting parts on cold days, set it for low temps and you can give the paint lots of times to flow and smooth out very nicely.

            I've also used hair dryers to cure paint, they kick out plenty of heat and generally work well. Issue is that they can kick up dust.


            • #7
              You don't need to heat the air, just the object. You DO need to keep plenty of free air around the new paint for a while. As mentioned above, a couple of IR floodlamps will work nicely. Not long ago they were used in most auto paint shops to speed curing. Using lamps of this type you would need to move them around a lot to get even heating, or put two or three on a post and just move from one side of your project to another.


              • #8
                For me, the appeal of the OP's plan to use an incandescent source
                is that no shopping, purchase or storage afterward is req'd.

                Anyone who ever burned a wrist on the housing of a traditional
                trouble light w/ a 100W bulb knows these bulbs radiate some
                warmth. It isn't that long ago that common practice for assisting
                winter start-up of outdoor power equipment & other equipment
                not equipped with some provision for warm-up was to place a
                bulb beside the object and shelter from wind.

                Edit: Change to personal perspective to reduce appearance of
                being argumentative. An accumulation of infrequently-used
                specialty items here is nearing the point of being unmanageable.

                Last edited by EddyCurr; 11-10-2014, 11:56 AM.


                • #9
                  I paint in my cold barn all the time. I use a large cardboard box - like from a TV (when they were big), welder, fridge or whatever... a 8x8 hole cut in the bottom for a small ceramic 120v heater, and a BBQ temperature reading fork stuck in the top of the box. Vary the temperature by fan speed and the moving a piece of wood that blocks the slot in the top. Easy...

                  I like the ceramic heater low warm air flow as it makes for even temperatures all over the work and box, and you have 1500w at your disposal. I doubt you'll get the casting to say 100F with just handful of household blubs... it take a lot more then that if you are in cold'ish room. Measure the casting temp for panting, not the air temperature. And.. a casting (unlike a car panel) can takes a long time to get up to temperature even with a heater.

                  I pre warm everything (large parts can take many hours) then paint, and when flashed off, leave it on at about 120-140F overnight. Don't handle the parts until cold - the rustoleum paint will be soft at those temps and you'll leave finger prints. For the "hammered" finish, don't heat the part too hot - it needs time to form the fish eyes and if too hot you'll just get a nice even gray..

                  One of many variations on the theme... I've painted entire machines this way by using plywood panels and tape.

                  Last edited by lakeside53; 11-10-2014, 12:01 PM.


                  • #10
                    I like Eddy's idea - heat the unit not the air, that way brushing the paint on will flow better not worse and almost everybody owns a lightbulb... cover the unit to get it up to optimum temps - they did that with old engines too - insulation helps the windchill factor and there will be passive windchill factors as the unit heats and creates its own thermal motion of air...


                    • #11
                      I painted a bike frame with rattle can primer and top in the midst of winter in my garage. I screened of a small part of the garage with tarp and heated that up with an electric oil heater so it was ~40F, then heated the frame with a hair dryer, sprayed, dried with a hair dryer and then left it 2-3x the recommended time before the next coat. That also helped me warm up in the meantime. It's held up well from many crashes and drops, so it's a workable option even if I'd rather have done it another way.


                      • #12
                        I think I would put a heater under the hollow casting to heat the casting and then let the casting heat the air inside your enclosure. Might seem like nothing is happening for a while, but when the casting finally comes up to temperature on the outside, it will stay there for a long while.
                        Weston Bye - Author, The Mechatronist column, Digital Machinist magazine
                        ~Practitioner of the Electromechanical Arts~


                        • #13
                          Originally posted by Weston Bye View Post
                          I think I would put a heater under the hollow casting to heat the casting and then let the casting heat the air inside your enclosure. Might seem like nothing is happening for a while, but when the casting finally comes up to temperature on the outside, it will stay there for a long while.
                          I would agree. With the bulb under or better yet, inside the casting, it will heat the casting while allowing free air flow around it. You may need to experiment, but I would start with one or two 40 Watt bulbs. I say 40 Watt because larger ones will tend to burn out faster with more heat concentrated in a single bulb. This is also more "green" because more of the heat will wind up in the casting you want to heat and less will be wasted to the surrounding area.

                          You may try using an electric iron (as in clothes iron) which has a thermostat to prevent overheating. And it will not burn out at an inopportune moment.

                          Do take precautions to avoid starting a fire.

                          PS: I also have used light bulbs. I have worked in TV stations and it is amazing just how fast small painted objects will dry when placed a foot or two under a 500W, 750W, or even 1KW lamp. But you have to watch it closely.
                          Paul A.

                          Make it fit.
                          You can't win and there is a penalty for trying!


                          • #14
                            I have an outside stand-pipe style faucet that I use for my ice rink. The heat tape died, so I built a box around it and use a 100W light bulb to heat it. It worked well the previous years, but did freeze up last year with temperatures down in the single digits. I imagine I get somewhere around a 20-30 degree temperature rise.

                            The light bulb worked well enough I'd try it for your application. I imagine you've got all the parts, so could give it a try before painting and see how it works.


                            • #15
                              I used to put my lunch can in the rod box for low-hydrogen rods when I got to work. At lunch it was piping hot. You wouldn't want to hold electrodes in a gloved hand longer than a minute.

                              Just an old fridge with the light hot wired to the plug, maybe 60-75W bulb. Always on and had perhaps
                              4-500 lb. of 7018, 80-C3, 110, 309. 10, 16 etc. Good thermal mass, much like your casting.