Painting in High Temperatures

[Caveman]

I was reading a thread about painting on humid days (don't so it) and thought I'd start a new thread since this is a slightly different topic and I haven't seen it covered.

Fortunately, where I used to live and will be returning to soon (in the desert near Palm Springs, California, United States) we often have single-digit humidity. I really love the low humidity! Unfortunately, along with the low humidity comes higher temperatures. During the summer, the temperature can get up into the low- to mid-120s °F (50 °C) range.

I'm new to airbrushing and was wondering what temperatures are best for painting and at what temperatures I should not paint at all. Does anyone have any experience with this or suggestions?

Is there a lower limit to painting temperatures? I don't really expect problems with lower temperatures in the winter. Our winters are so cold that sometimes I think about wearing socks with my sandals, shorts, and t-shirts. 

— Chuck

[peteski]

I wish I had your "problem"!    Not only is low humidity good for airbrushing, it is also great for resin-casting (as moisture creates those dreaded bubbles in the resin).

I have no experience airbrushing in your climate but I do know that the 1:1 automotive body shops thin their paint using different temperature reducers (thinners) for automotive paints. Those are available in cold, medium, and hot temperatures. What makes the difference it the solvents in the thinner have different evaporation rates. The cold reducer uses very fast-evaporating solvent ,while the hot temperature reducer has more slow-evaporating solvent.  That allows the paint to level out (in a liquid state) before the solvent evaporates.

I would say get some plastic spoons (they are excellent for paint tests) and practice airbrushing on them uisng whatever standard paints and thinners you'll be using.  You should be able to find an ideal setting of air pressure, nozzle opening, distance from the painted surface, and thiner-to-pint ration to achieve smooth paint jobs.

If you cant (I doubt that) then we could maybe look to see if we can find slower-evaporating solvents for your paints, or a drying retarder.

[Kisatchie]

I airbrushed solvent-based paints in many a New Orleans summer with temps in the 90s and high humidity. I never had any problems.

Acrylic paints were another story, however. I thought they dried too fast in the heat and clogged up the airbrush. There was one particular acrylic paint, though, that always sprayed properly for me. It was Accuflex/Modelflex??? Missouri Pacific blue. Don't know why.


Hmm... is that the paint
jar I spit in to get back
at Kiz for not buying me
enough bananas...?

[robert3985]

When I got serious about doing a lot of painting of models...when I starting doing work for customers...I decided I needed to take control of my painting environment by building a spray booth that would exhaust paint fumes to the outside and I could paint in my workshop all year round, day or night.

It was pretty simple to do, and I made it mostly out of 1/4" plywood, reinforced with 1X4 premium pine boards and a 3/4" base.  Dimensions are 23.75" X 25" X 25" deep and it fits just right on a prefab small cabinet, with a drawer and cupboard underneath.  It's powered by a Dayton 1/20th hp, 265 cfm, continuous-run, shaded-pole 115vac blower, and filtration is by removable furnace filters.

It's lit nowadays with two 15w 5000k LED bulbs, which is what my layout is lit by.

Sure takes the worry out of only painting when the weather's good, or it's daytime, or it's not too hot, or cold. 

With the continuous-run blower, I can put my enamel painted plastic models in it for a couple of days with the blower going and never smell a fume while the paint cures.  I also put my big ultrasonic cleaner in it when cleaning investment off my castings or stripping paint/cleaning brass models with my high-powered cleaning solution that gives off an unbearable ammonia smell.  No fumes.  I also use it when cleaning parts with Bestine/Heptane.

Total cost for it would be about $125 to $150 bucks, with the blower being the main expense.

It has certainly been one of my best, most useful projects that I've completed over the past 20 years.

Or, you can spend a lot more for a commercial version, which if it's vented outdoors, will do the same thing as mine as long as the blower being used is continuous-run.

Just sayin'.... 

Cheerio!
Bob Gilmore

[Caveman]

@peteski — It's not really a problem. The heat just sounds dramatic to people that aren't used to it. If I have to work outside, I'd rather work in 120°F at 4% humidity than 90°F at 90% humidity any day. I don't handle humidity well. There are a lot of adjustments to everyday tasks to accommodate the heat, but once you figure those out you're fine. You're comment gave me an idea: I should check with some of the local auto body shops to see what issues they have and what they do to deal with those issues. As far as I know they don't shut down during the summer (some local businesses do).

@Kisatchie — I usually don't have to deal with humidity. I wonder if adding more thinner to the paint would help slow down the drying in the heat.

@robert3985 — I've been thinking about building a paint booth. Painting would be much more enjoyable indoors with the A/C running. Does your paint booth have a door on it? I had thought about using a kitchen cabinet for the basic structure of a spray booth. It sounds like yours fits on top of a kitchen cabinet. I was thinking the door, which doesn't seal, might help keep some of the dust (and grandkids) out, but wouldn't interfere with air flow through the fan. How is the spray booth as far as fire danger? If you spray something that might be flammable, can sparks in the blower motor or lights ignite the vapor? Do you just run the vent out a window or door?

[robert3985]

@Kisatchie — I usually don't have to deal with humidity. I wonder if adding more thinner to the paint would help slow down the drying in the heat.

@robert3985 — I've been thinking about building a paint booth. Painting would be much more enjoyable indoors with the A/C running. Does your paint booth have a door on it? I had thought about using a kitchen cabinet for the basic structure of a spray booth. It sounds like yours fits on top of a kitchen cabinet. I was thinking the door, which doesn't seal, might help keep some of the dust (and grandkids) out, but wouldn't interfere with air flow through the fan. How is the spray booth as far as fire danger? If you spray something that might be flammable, can sparks in the blower motor or lights ignite the vapor? Do you just run the vent out a window or door?

Most model paints have a retarder you can put in them to make them dry slower.  You might give that a try.  I've done it with a couple of brands of acrylic paints on the colors I'm using for motive power and passenger equipment bodies, because it means the paint lasts longer in my airbrush bucket, and it goes on the model wet for a really nice, glossy finish.

As to my spray booth having doors.  Nope, but that's not a bad idea.  You could build small selves on the inside of them to store your paints, or your airbrush accessories.  I have a really good electrostatic filter on my furnace, so I don't have a dust, pollen or cat-hair problem.

The motor on my blower sticks out the back, so it's not in the airstream.  It is made for venting, although nothing in its specs say it's for flammable atmospheres, I've never had any problems with explosions using some pretty potent flammable paints for various projects.  Yup, it's vented out one side of my workshop window with a piece of extra wide shelving stock, finished on both sides replacing the glass...all sealed up and weather tight.  Flexible aluminum dryer ducting goes from the blower to a quality dryer flapper on the outside of the shelving stock piece.

I used a write-up in Model Railroader about making a spray booth as my initial pattern with a couple of improvements.  It's been long enough that I can't remember much more about it than that, but it was an easy job, with great benefits!

Edit: Here's a photo of my model train workshop and my spraybooth up against the window.  Excuse the stuff stacked on top of it!


Cheerio!
Bob Gilmore

[Kisatchie]

@Kisatchie — I usually don't have to deal with humidity. I wonder if adding more thinner to the paint would help slow down the drying in the heat.

That's funny. Even airbrushing in high (90s) temps, I often added accelerator to my Scalecoat II paint to make it dry faster. It worked great!


Hmm... I wish Kiz would
use an accelerator when
it's time for him to feed me...

[Caveman]

As to my spray booth having doors.  Nope, but that's not a bad idea.  You could build small selves on the inside of them to store your paints, or your airbrush accessories.  I have a really good electrostatic filter on my furnace, so I don't have a dust, pollen or cat-hair problem.

I don't  know what my next house or apartment will be like, but the last one I had leaked in the high winds and/or sand storms. At my front door I'd get little sand dunes built up. (Maybe I should have sprayed them with white glue and water to make realistic N scale sand dunes.) I tried replacing the weatherstripping myself twice and then had the apartment maintenance guy replace it and we were never able to get it to seal completely. I had planned to get one of those HEPA filter units, but never got around to it before I moved.

There's a reason they built one of the largest wind farms in the world at the east end of the San Gorgonio Pass: lots of wind.

See it larger on Flickr.

The motor on my blower sticks out the back, so it's not in the airstream.  It is made for venting, although nothing in its specs say it's for flammable atmospheres, I've never had any problems with explosions using some pretty potent flammable paints for various projects.  Yup, it's vented out one side of my workshop window with a piece of extra wide shelving stock, finished on both sides replacing the glass...all sealed up and weather tight.  Flexible aluminum dryer ducting goes from the blower to a quality dryer flapper on the outside of the shelving stock piece.

I used a write-up in Model Railroader about making a spray booth as my initial pattern with a couple of improvements.  It's been long enough that I can't remember much more about it than that, but it was an easy job, with great benefits!

I was thinking about a piece of plywood or something in the window as you have done. A piece of white melamine shelving would make it look nicer for the neighbors.

I see you built your spray booth on top of the cabinet. I was going to use the cabinet itself for the booth. I like your idea much better. Would painting the interior of the booth white make the lighting better or would that be overkill?

Edit: Fixed photo so it will display properly.