Warming paint cans.

[aurfalien]

Hi,

So I've read several posts on the importance of warming paints in general, wether spray or brush.

Some even say to heat the can super hot to the touch.

I've been using very warm, not hot to the touch with my cans and notced the bottoms start to bubble out.

Does any one mind giving me guidance on this?

I'll simply dial down the heat to luke warm and let the can soak for a bit.

[Nacho Z]

I just run hot tap water into an old water pitcher.  The cylindrical, tall, old fashioned one.  I put the can of paint into the pitcher and leave it in there for a few minutes.  I take the can out, shake the heck out of it, while at the same time running more hot water back into the pitcher.  I do this two or three times until I feel the can of paint is uniformly warm. 

[wilderness1989]

I just run hot tap water into an old water pitcher.  The cylindrical, tall, old fashioned one.  I put the can of paint into the pitcher and leave it in there for a few minutes.  I take the can out, shake the heck out of it, while at the same time running more hot water back intoditto the pitcher.  I do this two or three times until I feel the can of paint is uniformly warm. 

DITTO NACHO.   IF YOU GET THE CANS TO HOT YOU MIGHT CREAT A BOMB.

[detailstymied]

... the importance of warming paints ... heat the can super hot to the touch....

for years i've heard "there are no silly questions". well ... some are definitely borderline.

[StevenGuthmiller]

I usually just run hot tap water into a small bathroom sink that is close to my shop.

Drop the can in & leave it for 5 minutes.

I really don't know what the benefit would be from getting the can so hot you can't touch it. Unless you're hoping for disability payments when it blows up on you.

 

Steve

[aurfalien]

Ok cool.

Well, I definatly see the bottoms buldging out to the point were a can couldn't lay upright.

Was curious if any one else had this same thing.

I'll stick to luke warm as the super hot to the touch definatly buldges the cans.

 

[Tom Geiger]

The idea is to "warm" the can, not superheat it!    There was a story about heating one up in a small pot of water on the stove... and forgetting about it... end result was a purple kitchen...  at least nobody got hurt on that one.  Could've been quite different.

Edited July 19, 2015 by Tom Geiger

[Deano]

The idea is to "warm" the can, not superheat it!    There was a story about heating one up in a small pot of water on the stove... and forgetting about it... end result was a purple kitchen...  at least nobody got hurt on that one.  Could've been quite different.

I know a guy who did that very thing; his wife got a redecorated kitchen out of the deal.

[aurfalien]

Well,  in terms of vigorously shaking the can, Tamiyas site says to swirl the can so that the ball inside rides around the cans wall.

Wondering if any one notices a difference in quality were they shook the can vigorously vs swirling it around?

[Nacho Z]

Well,  in terms of vigorously shaking the can, Tamiyas site says to swirl the can so that the ball inside rides around the cans wall.

Wondering if any one notices a difference in quality were they shook the can vigorously vs swirling it around?

Yes, I have heard/read about it but I have never, that I can remember, had a poor outcome because I shook the can.  I think the possibility of a poor outcome from not shaking the can enough would be greater than the possibility of a poor outcome from shaking it.

[High octane]

I usually shake the can to mix the paint, I then put it in a pot of warm water, cover it with a towel for 'bout six minutes. I remove the can, dry it, shake it again, and then spray. I wait 15 minutes, put more warm water in the pot for 6 minutes, etc. This seems to work for me as I've been doing this for several years now. The can is already "under pressure" when you buy it, so shaking it won't increase the pressure but it will mix the paint.

[aurfalien]

Ok ool, many thanks gents, many thanks.

I know it seems like silly questions but I'd like to start with good habits early rather then break bad habits later.

[StevenGuthmiller]

It surely doesn't hurt to do a little "swirling" as well as shaking.

If you've ever used a metallic airbrush paint such as from MCW you would see how caked the metal flakes can get to the bottom of the jar.

It can take a little scraping to get it loosened up again after it sits for a while.

A little swirling of the ball around the bottom of the can could only help to get those sediments off of the bottom.

 

Steve

[dimaxion]

    I will add to this discussion . In the '70's when Pactra introduced the Jade Metallic Flake Paint I jumped at it . I like green the best . This failure was my last attempt to build a non - Factory Stock . I took the can Outside in colder weather to apply a Super Custom Finish . 36 degrees IIRC outside to paint this Project . I had the can sitting on the Furnace Duct for an hour at least . Entered the 'Paint Zone" .. ready .. aim .. NO SPRAY . I remembered about the recent tip of hot water ..  

     On the Stove for a warm up ..  to the 'Paint Zone' .. no spray . Third time .. NO SPRAY . More Heat , can hot and into the "Paint Zone" for attempt #4 . Push the Nozzle and BOOM !  The Top of the cam released expelling the Contents . On my face - project - surrounding Environment spoiling all three . Two weeks before the paint was cleaned up . This was ion the Days before Paint Removal Procedures for Model car Builders .. I did not use Pactra Flakey paint again . The Metallic Chunks were too large for the Nozzle passageway . Physics 101 : Hot things get hotter before cooling off . The Cold Air introduced at the Nozzle contracted the top of the can . Pressure inside the Can did what it was intended to do .

    I swirl , shake and have used a Mini Shaker for Bottled paints since 2001 . Great tool foe MCW Paint . I do not have a shaker large enough for Paint Cans .. 

     Thanx ..

[Pete J.]

This subject seems to come up all to often and there is a lot of anecdotal information out there that may or may not be correct.  Before you get into this, I suggest that you read the following investigation of an legal expert witness on aerosol cans and DOT requirements regarding internal pressure and tests done for court cases. http://www.chemaxx.com/aerosol12a.htm  Personally I found it very interesting and if I am reading it right, explosion due to heat well below 175 degrees is unlikely.  You are more likely to have issues with inadvertent punctures than explosions from heating the can.  If you stay below 125 degees(well below what a water heater or food dehydrator operate at) you should be safe.  Boiling water or any association with a stove is likely to result in a disaster.  If the can is bulging, carefully remove it from the premises and  let it cool and throw it away.  You got away with one and don't do that again. 

[XJ6]

It surely doesn't hurt to do a little "swirling" as well as shaking.

If you've ever used a metallic airbrush paint such as from MCW you would see how caked the metal flakes can get to the bottom of the jar.

It can take a little scraping to get it loosened up again after it sits for a while.

A little swirling of the ball around the bottom of the can could only help to get those sediments off of the bottom.

 

Steve

That's interesting, never would have thought of that sure does make sense Good advice ?.  Thanks for sharing a Great Tip ?

XJ6?

[mkucaba]

I've left cans sit in the direct sun here(in Mesa) and have never had a problem.

FWIW this "ëxplosion" (like the can heated on the stove) can only happen if there is something to ignite it. A can just bursting is just a can bursting, not an explosion,but I wouldn't want to be too close .

And just for all the Experts here, I worked at an aerosol valve manufacturer. I was in the Machine repair end and my brother & a friend were in Quality control.

[aurfalien]

Hmm, well it seems a good discussion and not so silly after all, I'm stoked.

I've been shaking and swirling as well.

[John Clutch]

The purpose of warming up the spray can is to increase the pressure inside. The higher the pressure, the more duration you get out of it, allowing you to use more of the paint that would normally be left after the pressure drops to atmospheric pressure. Warming the can also helps to thin out the paint as well, so if you start a paint job with a warm can, you'll need to finish the paint job with a warm can, otherwise you can see the difference between the panels you paint. You DO NOT raise the temperature to the point that you can't hold it. It's dangerous to have the bottom of the can bulging out for obvious reasons, but the not so obvious reason is that the hotter the can, the bigger the temperature difference is as it cools.  You start spraying the body when the can is hot, the paint is very thin, and as the can cools at a rapid rate, so does the paint, resulting in the paint being thicker......

Be constant. Warm water is all you need. Spray the paint until you can feel the warmth of the can disappear. Then put the can back in the warm water. And remember to shake the can to mix the paint and also dry the can, so your not spraying water that's dripping off the can.

Guys that run nitrous warm the bottle for similar reason. The solenoids are rated at 1800 psi bottle pressure. When you see them purging nitrous on the starting line, that's so they lower the bottle pressure to 1800psi. Too high of a pressure might over power the track, too little pressure and the car is a pooch. 

[detailstymied]

BE CAREFUL - THE COFFEE IS HOT!!!

[DaveM]

Boyle's law also works against us, as spraying the paint decreases the temperature.  Warming the can slowly (I use a sink filled with moderately hot tap water, and change it a couple of times)  helps with both the pressure and the consistency of the paint.  I am  very careful with the Testor's Lacquers in the automotive colors, as I have had a couple of those cans leak their contents through pinholes before.  (I decant them and thin them for an airbrush, as they are a bit thick and have lousy nozzles)  

 

One modeler here gets around Boyle's law by shooting pretty thin coats, and reheating the can between coats.  He gets the can hotter for each coat, as the volume and pressure decrease as the can empties.  By his last coat, he can't hold the can with a bare hand, and he gets incredible paint jobs with a spray can.  I am afraid to get things anywhere near that hot, so I live with falling pressures towards the end of the can.  I am starting to rely less on the cans and much more on my airbrush.  I feel more comfortable with the airbrush anyways, as I have much better control. 

[Pete J.]

Boyle's law also works against us, as spraying the paint decreases the temperature.  Warming the can slowly (I use a sink filled with moderately hot tap water, and change it a couple of times)  helps with both the pressure and the consistency of the paint.  I am  very careful with the Testor's Lacquers in the automotive colors, as I have had a couple of those cans leak their contents through pinholes before.  (I decant them and thin them for an airbrush, as they are a bit thick and have lousy nozzles)  

 

One modeler here gets around Boyle's law by shooting pretty thin coats, and reheating the can between coats.  He gets the can hotter for each coat, as the volume and pressure decrease as the can empties.  By his last coat, he can't hold the can with a bare hand, and he gets incredible paint jobs with a spray can.  I am afraid to get things anywhere near that hot, so I live with falling pressures towards the end of the can.  I am starting to rely less on the cans and much more on my airbrush.  I feel more comfortable with the airbrush anyways, as I have much better control. 

This is probably one of the best reasons for decanting the paint and blowing it through an airbrush.  Instead of using heat to control viscosity, pressure and volume, a good airbrush can do all of these constantly.  Not to mention that you don't have to stop half way through and reheat the paint.  I know, I know, not everyone wants to spend the bucks on an airbrush and a compressor, but frankly, it solves all of these problems very nicely.  Of course then you have to learn how to use an airbrush, which everyone doesn't want to do either. 

[oldnslow]

I've had luck heating my paint cans with an old adjustable heat iron, set on it's lowest setting. I turn the iron upside down in my bench vice, plug it in and set the paint I'm going to use on the bottom of the iron. Shake the paint as usual before it's put on the iron and after. The cans warm up to a comfortable temp to hold in your hand and the paint lays down really well with a nice gloss, it also dries faster. To test the temp of your iron place an open can half full of water on it, let it sit for about 5 minutes and carefully check the can to see if you can hold it. Better safe than sorry.

Edited July 26, 2015 by oldnslow

[Art Anderson]

    I will add to this discussion . In the '70's when Pactra introduced the Jade Metallic Flake Paint I jumped at it . I like green the best . This failure was my last attempt to build a non - Factory Stock . I took the can Outside in colder weather to apply a Super Custom Finish . 36 degrees IIRC outside to paint this Project . I had the can sitting on the Furnace Duct for an hour at least . Entered the 'Paint Zone" .. ready .. aim .. NO SPRAY . I remembered about the recent tip of hot water ..  

     On the Stove for a warm up ..  to the 'Paint Zone' .. no spray . Third time .. NO SPRAY . More Heat , can hot and into the "Paint Zone" for attempt #4 . Push the Nozzle and BOOM !  The Top of the cam released expelling the Contents . On my face - project - surrounding Environment spoiling all three . Two weeks before the paint was cleaned up . This was ion the Days before Paint Removal Procedures for Model car Builders .. I did not use Pactra Flakey paint again . The Metallic Chunks were too large for the Nozzle passageway . Physics 101 : Hot things get hotter before cooling off . The Cold Air introduced at the Nozzle contracted the top of the can . Pressure inside the Can did what it was intended to do .

    I swirl , shake and have used a Mini Shaker for Bottled paints since 2001 . Great tool foe MCW Paint . I do not have a shaker large enough for Paint Cans .. 

     Thanx ..

All of this brings up a SERIOUS safety issue!  When aerosol (spray) cans of everything came into being,the propellant was Freon (a refrigerant), but Freon (a nastly CFC compound known to be bad for the environment) was banned over 20 years ago.

Most, if not all, modern aerosols use PROPANE as their propellant.  As almost everyone here knows, propane is a flammable gas, and if suddenly released in the presence of an open flame, will explode rather violently.

I would never EVER attempt to warm up a spray can over an open flame at any time, PERIOD.

Art

[dimaxion]

I agree with Art . I did heat the can in a Pan with water . It was heated better than on the Furnace Duct . Directly on the stove and open flame creates explosion . The Freon Escaping past the Flakes stuck in the Nozzle cooled the top of the can off quickly  . The rest you know . Thanx Art ..