Cold enamel paint a problem?

[Mushtang]

Yesterday I was working on my US Patriot Missile nosecone which is hollow plastic. I sanded it all over to remove the seam (two halves had been attached at the factory) and put on a couple of coats of enamel primer.

The can of primer was room temperature when I sprayed it on and it did very well. It dried fairly quickly and I was able to get 2 coats on and both dried, so right before bed I put on the first coat of white enamel paint.

The white paint can had been sitting in the garage and was cold (I'd guess in the 40's or 50's) and I didn't know if cold paint would be a problem or not. I shook it up really well before spraying and gave the nosecone a nice thin first coat. There was some primer showing through but the first coat is supposed to be thin. That was last night, and I hung the nosecone in the kitchen overnight to dry.

This morning the white paint was still very tacky to the touch. The two coats of primer seemed to dry in less than an hour each so I'm very confused as to why the white wasn't dry after 8 hours in a 70 degree kitchen. I haven't done a lot of model painting and don't know what all the tricks of painting are yet.

Was it because the paint was cold when I sprayed it on?
If so, will giving it another coat of room temperature paint tonight fix the problem?

 

[rcktnut]

You should let any spray cans warm up before spraying. That would not be the cause of the paint still being tacky though. What is the paint brand/type? Not all spray paints are fast drying.

 

[Mushtang]

What is the paint brand/type? Not all spray paints are fast drying.

I know they're both the same brand, I made sure of that when I bought the paints. I'll check the labels tonight and see if the primer is a special "fast drying" primer.

I suppose if the white paint is dry by the time I get home tonight I'll know I have to wait 24 hours between coats if I want to paint over dry paint. Is that the best way, or would applying the 2nd coat over a still tacky 1st coat be a problem?

 

[RocketManDan]

I know they're both the same brand, I made sure of that when I bought the paints. I'll check the labels tonight and see if the primer is a special "fast drying" primer.

I suppose if the white paint is dry by the time I get home tonight I'll know I have to wait 24 hours between coats if I want to paint over dry paint. Is that the best way, or would applying the 2nd coat over a still tacky 1st coat be a problem?

What did it say on the can?

 

[Marc_G]

I agree with Dan... what does the can say regarding cure time?

Generally speaking, one of the reasons I don't like working with enamels is that very often they have extended drying times, and even in the best case 24 hours is often not "fully dry." I've had trouble spraying them cold, trouble spraying them hot, though often spraying in middling weather after warming the can gave a good result.

For this reason I switched to Lacquers which tend to be more forgiving in my hands. For the winter I've switched to water-based acrylics via airbrush and am having a blast with that. Now that I've got the brush and a CO2 bottle in lieu of compressor, my per-rocket (LPR) paint cost is probably ~$1 versus probably $2-3 with the lacquers I was using. Of course, I invested in lots of colors so I probably need to paint lots of rockets to catch up...

OVerall, I would avoid spraying enamel in cold conditions and try a different paint.

Lacquer rattlecans will take longer to dry in the cold but will still be reasonably dry in a couple hours.

Marc

 

[o1d_dude]

Micromeister recommends soaking the rattlecan in body temperature water before spraying. I've done this in cold weather and had very acceptable results.

I spray outside at all times. When it's cold or overly hot I bring the rocket inside to cure.

IIRC most rattlecan paint has a recommended temperature window of 60-90 degrees. With pre-warmed aerosols, you can cheat on the low temperature a bit but not so much in the higher temps as the paint dries before it hits the surface to be painted.

 

[luke strawwalker]

Warm paint cans are ALWAYS preferable to cold ones...

1) the paint viscosity is slightly lower when it's warm...
2) the propellant has more latent heat, therefore raising the "head pressure" in the can and increasing the spraying pressure somewhat, which gives a finer atomization, and a wider spray pattern (the spray pattern and droplet size is directly affected by the spray pressure, and the pattern narrows and droplets get bigger as the pressure decreases. The propellant in the can is a low cryogen which "boils off" as you paint, removing latent heat from the can, in effect, "refrigerating" it... so it's better for the can to start off warmer.
3) the warmer paint and solvent will have more latent heat content, helping it to evaporate faster.

Warming a can of paint is pretty easy. The best way is to store them in the house in a temperature controlled environment-- especially in an area that's usually warmer, like a utility room. If that's a non-starter in your home due to family objections, then the next best thing is to set the can of paint into a bowl or shallow bucket of hot water (not so hot that you can't stick your hand in it) and give it a half hour to an hour for the temperature to stabilize and "soak into" the can. Don't heat the can with infrared bulbs or setting them close to a space heater-- you can potentially overheat the can, leading to overpressurization and causing the can to rupture forcefully.

Warm paint cans can overcome quite a bit of it being rather cold in the spray environment... I recently painted a rocket outside in weather in the 30's by simply stepping out on the porch, applying the paint, and bringing the can and rocket back inside with me and setting it up in the utility room to dry between coats. Came out fine. Of course this isn't recommended procedure and your results may vary... test with the materials you're using in your environment before applying to the rocket this way.

Good luck! OL JR

 

[Mushtang]

What did it say on the can?

Both the white paint and the gray primer are Rustoleum Enamel. The white is Gloss Protective Enamel, and the primer is most definitely marked as Quick Dry.

When I got home from work tonight the white was STILL tacky to the touch. So I gave it another coat of white paint from the now room temperature can that has been inside all day.

 

[nukemmcssret]

Both the white paint and the gray primer are Rustoleum Enamel. The white is Gloss Protective Enamel, and the primer is most definitely marked as Quick Dry.

When I got home from work tonight the white was STILL tacky to the touch. So I gave it another coat of white paint from the now room temperature can that has been inside all day.

Try a hair dryer on low and don't melt the cone. Not the can blow dry the nose cone.

 

[rcktnut]

I have some of the Rustoleum Protective enamel, it is not a fast drying paint, but should not be tacky that long at room temp anyway. The Rustoleum professional series is a fast drying paint, I use that also. Actually I use alot of differant brands depending on the color I want. You just have to read directions and paint accordingly.

The slower drying paints IMO provide a nicer finish,they have more time to "lay down" providing you keep the dust away while they are drying.

I know some primers say you can apply the finish coat after 1 hour but I always wait at least a day. I sand between primer and finish coats, better after a day to do that.

 

[RocketManDan]

Sometimes I let my primers dry a few days. I'm not in a rush to finish a rocket and it's not like I'm going to launch it right away, so my theroy is why rush? If the weather isn't cooperating who cares? Just relax and wait it out. There's nothing worse than putting all that time, money and effort into building a rocket than to rush the paint.

I don't know about anyone else, but I have had issue with Rustoleum Professional Automotive Formula, but only in the "Gloss White Enamel" comes out like cottage cheese. Just wanted to put that out there and see if anyone else had the same problem. It wasn't just one can, but I exchanged it for another can...same issue. Now it sits in my cabinet waiting to be used on something other than a rocket.

 

[Mushtang]

I put on a second coat with a room temperature can, and hours later it too is still tacky. I was able to put on a 1" stripe of red paint, two coats, in the same time and it is fully dry to the touch.

Perhaps the Gloss White Enamel is a very long time to dry paint? But I've used the same can on other rockets recently and it dried a LOT faster. The only difference was that the can was cold when I used it yesterday.

I'll try the hair dryer if it's still tacky by tomorrow. If it's still tacky by the weekend I'll have to try and buy a replacement nose cone and a can of flat white paint.

I can put a clear coat over the top of flat white and make it shiny looking, right? I'm planning on a clear coat regardless.

 

[MarkII]

I don't know that a long dry time is associated with using a cold can of paint. Usually the big problem encountered is that the paint runs like water and coats very poorly when it is cold. If you achieved an even coat with no runs that doesn't subsequently crackle or wrinkle then you are about 99.5% there. I'd call that a win. The long dry time is probably due to the fact that it is (a) enamel, and (b) you are in the cold part of the year. "Room temperature" is a relative thing, and even a well-heated house is not nearly as warm in December as it is in July. I wouldn't worry about it; just give the paint more time to work itself out. If it is still tacky a month from now, then perhaps that would indicate a problem. I give regular enamel a full week, and acrylic enamel a couple of days (or more) to dry in the summer. Thicker coats and multiple coats of paint take longer too, of course. I don't attempt to use spray paint at all once the weather turns cold. I postpone any further painting until the following spring.

 

[RocketManDan]

I don't know that a long dry time is associated with using a cold can of paint. Usually the big problem encountered is that the paint runs like water and coats very poorly when it is cold. If you achieved an even coat with no runs that doesn't subsequently crackle or wrinkle then you are about 99.5% there. I'd call that a win. The long dry time is probably due to the fact that it is (a) enamel, and (b) you are in the cold part of the year. "Room temperature" is a relative thing, and even a well-heated house is not nearly as warm in December as it is in July. I wouldn't worry about it; just give the paint more time to work itself out. If it is still tacky a month from now, then perhaps that would indicate a problem. I give regular enamel a full week, and acrylic enamel a couple of days (or more) to dry in the summer. Thicker coats and multiple coats of paint take longer too, of course. I don't attempt to use spray paint at all once the weather turns cold. I postpone any further painting until the following spring.

Marc makes an important point here when painting. I do all my building from Oct-Feb. The projects I am working on I leave primer until Spring and then I spray the color. If I get an exceptional warm day then I might spray some color, but this is my routine. I then use the summer months to launch. I liev in Southern CA and yes the weather is nice, but we do get some cold days and it does rain. I just would rather not chance it.

 

[Mushtang]

The second coat of paint was dry to the touch this morning, so I'm guessing that the cold paint can definitely changed something about the paint and kept it from setting.

The other colors I've painted using room temperature paint cans all seemed to dry just fine.

I appreciate everyone's help and input. I've definitely learned not to paint with cold cans anymore.

 

[rcktnut]

I put on a second coat with a room temperature can, and hours later it too is still tacky. I was able to put on a 1" stripe of red paint, two coats, in the same time and it is fully dry to the touch.

Perhaps the Gloss White Enamel is a very long time to dry paint? But I've used the same can on other rockets recently and it dried a LOT faster. The only difference was that the can was cold when I used it yesterday.

I'll try the hair dryer if it's still tacky by tomorrow. If it's still tacky by the weekend I'll have to try and buy a replacement nose cone and a can of flat white paint.

I can put a clear coat over the top of flat white and make it shiny looking, right? I'm planning on a clear coat regardless.

Edit: Good to hear it's drying!!!

Like Mark said, give it time!!! If your happy the way it looks leave it alone, it will dry. Check it out on Sunday and give us an update.