View Full Version : Incandescent light bulb heating for drying paint at low temps...

11-10-2014, 09:43 AM
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?


loose nut
11-10-2014, 10:07 AM
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.

11-10-2014, 10:28 AM
Infra red patio heater?

11-10-2014, 10:34 AM
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.


11-10-2014, 10:43 AM
I'd use a heat bulb like they use to keep food hot.

11-10-2014, 11:06 AM
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.

11-10-2014, 11:12 AM
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.

11-10-2014, 11:36 AM
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.


11-10-2014, 11:42 AM
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.

http://i238.photobucket.com/albums/ff150/lakeside53/misc%20linked%20uploads/DSC_5962Medium.jpg (http://s238.photobucket.com/user/lakeside53/media/misc%20linked%20uploads/DSC_5962Medium.jpg.html)
http://i238.photobucket.com/albums/ff150/lakeside53/misc%20linked%20uploads/DSC_5964Medium.jpg (http://s238.photobucket.com/user/lakeside53/media/misc%20linked%20uploads/DSC_5964Medium.jpg.html)

A.K. Boomer
11-10-2014, 11:47 AM
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...

11-10-2014, 12:44 PM
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.

Weston Bye
11-10-2014, 01:01 PM
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.

Paul Alciatore
11-10-2014, 01:45 PM
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.

11-10-2014, 06:00 PM
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.

11-10-2014, 06:12 PM
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.

11-10-2014, 06:19 PM
Go to the tractor/farm supply store and grab some nice cheap brooder bulbs- they'll heat the surface quickly and evenly and they are not hot enough or have any sparking contacts to worry about burning anything. I use them in my sort-of-heated workshop on epoxy glue-ups in the dead of winter (sub zero outside).

11-10-2014, 06:23 PM
Remember ALL electric heaters are 100% efficient. So a 100 watt light bulb produces 345 BTU of heat per hour, same as any other electrical device. Putting a light bulb or heater of any kind at the bottom under the hollow casting will do a fine job, as it will create a chimney effect of warm air rising up through the casting. Warm it up, turn the bulb off, turn it back on until the paint drys. Get back to work.

11-10-2014, 08:20 PM
What a bunch of good practical suggestions, thanks all! Wish I thought of the big cardboard box idea, would have been alot easier/cheaper... oh well.

Testing: I'll see how long it takes to bring the casting up to temp this week, didn't think of that... V8 - why didn't I think of that moment. :)

Looks like it'll be an all day affair when it comes to actually painting so I'll have to wait for the weekend. I'll re-read the specs on the paint but think I have to wait a couple hours between coats but not more than 4 or you have to wait 7 days for the next coat. Planning on a couple coats primer followed by a couple brushed on coats.

Before all that though... what I discovered today: bondo? or something like it?... I applied a good thick coat of Citristrip early morning last Saturday, Sunday I scraped the vast majority of the original paint(s) down to primer. Turns out it has 1 coat rust-red primer, 1 coat gray, 1 top coat of some cracking, putrid green (why would anyone ever choose that color, but then again, maybe someone will say that about this latest paint). Good riddance. Anyway, after cleaning that best I could I applied one more Citristrip coat last night then high pressured washed it off today. Towel dried best I could, rolled back into the cave where it's sat with a fan blowing on it for a couple hours now.

It was after the pressure wash that I discovered the black bondo stuff. New to me... so, I didn't know they did that. Wherever there is a void or bit of un-fairness, there the bondo could be found. I can't imagine buying enough tubes of JB-Weld even if it would fill the voids with something good and hard. So, what to use here? Bondo? Some other relatively hard resin?

Thanks again for all the great ideas/input...

11-10-2014, 08:36 PM
"Bondo" or other car body filler works fine. Sets really quickly - multiple application / sanding in a few hors. JB weld would have to cure for a day before sanding. For small voids use one other metalglaze like products.

Check for adhesion to the existing stuff though. I has a BP that has a black filler (some type of spray putty), and it had absorbed oil though surface cracks. I washed and degreased many times. Seem ok at first but "bondo" body filler just fell off with any pressure. I has to strip it back to the bare metal.

11-10-2014, 11:23 PM
Thanks lakeside53, maybe some JB for the deeper voids then, I'm in no rush here. Wonder if primer stuck well on your BP, could you Bondo/Evercoat over the primer?

Quick test looking good so far... popped a 100w bulb inside the casting a couple hours ago. Outside temp atm is 53°, the bottom of the column just measured 61°. Figured I'd just leave it on overnight to get it good and dry, will check the temp again in the morning.

11-11-2014, 12:43 AM
High build primer filler, mustard coloured stuff, thin with ordinary thinner, mind I've used gun wash many times as it's cheap, you can build up quite a thickness with it.

11-11-2014, 01:11 AM
Thanks lakeside53, maybe some JB for the deeper voids then, I'm in no rush here. Wonder if primer stuck well on your BP, could you Bondo/Evercoat over the primer?


You can apply Bondo in thick coats (you need to be quick with large masses - it sets up fast). There's no advantage in using an epoxy for purely cosmetic uses. Yes, if the primer and spray putty was in good shape, I could have used Bondo over it.

11-30-2014, 08:49 PM
Quick test looking good so far... popped a 100w bulb inside the casting a couple hours ago. Outside temp atm is 53°, the bottom of the column just measured 61°. Figured I'd just leave it on overnight to get it good and dry, will check the temp again in the morning.Any chance for an update on the test results observed
with a 100W bulb positioned inside the casting overnight?


11-30-2014, 09:58 PM
Any chance for an update on the test results observed
with a 100W bulb positioned inside the casting overnight?

Hi Eddy, I think it's going to work pretty well thanks to all the ideas gleaned on this thread... I left the 100W bulb inside of the main base casting for a couple days then check the outside temp of the casting in the morning when it was about 30° outside temp. The casting was 53°, so about a 23° increase, not bad.

Since I told myself it was time for a new work light anyways, I ordered this from Amazon:

Designers Edge L113 Industrial Impact-Resistant Untippable-Spring Mounted Portable Halogen Work Light, Green, 500-Watt

...it's pretty well made, fits inside the casting, and handy to have the light at whatever angle you want, and definitely warmer than a 100W bulb. This will work just peachy for bringing the base casting up to and holding paint temp.

Also, my old space heater was... getting... old, so, following lakeside53's advice... got a real nice little (about the size of a shoebox that only draws 1200W on high and 800W on low). Actually, what the Kill A Watt meter told me: Low: 6.67A, 770W - High: 9.90A, 1100W.

Crane #EE-6490 1200-Watt Crane Ceramic PTC Heater

I was concerned about how flammable the cardboard would be but this search result has me feeling a little better about it:

ignition point for cardboard is 427 degrees Celsius, or 800.6 degrees Fahrenheit

...hope it's accurate. Still plan on planting the heater between a couple cinder blocks though.

Reason I didn't want to use just any old heater... I have a 10A limit with something else I found to help with this, a thermocouple. Heard of them before but didn't know what they were or were for...:

IMAGEŽ All-purpose Temperature Controller STC-1000 With 2M Cable Cooling/Heating

I picked up a couple of them and have them mounted in small Radio Shack project boxes atm, just need to finish wiring them up. Going to use one on the halogen work light and the other one driving the heater & circulating fans. There's lots of tutes out there of folks using them for all kinds of stuff, i.e. heated aquariums, home brewers, meat smokers. Here's one I bookmarked:

DIY STC-1000 2-Stage Temperature Controller Wiring Diagram with Indicator Lights

This all might be old news to you and probably others here, but it's new to me... I've got high hopes. :)

11-30-2014, 10:06 PM
Very interesting, thanks for a thorough write-up.

First I've heard of the STC-1000 2-stage Temperature Controller.