Post by Zeebzob on Nov 30, 2009 14:52:57 GMT -7
Nov 30, 2009 11:25:22 GMT -7 @alchemist3136 said:
Warming paint - I put a soup pan of water on the stove top to simmer. Before each coat, I stand the paint can in the pan; 1 minute for tall cans and 30 seconds for short cans. Then I go out and spray a thin coat, leaving the water on simmer for the next coat. By the time I'm done with the multiple thin coats for a specific color, I will have refilled the soup pan with water.
Hello. I'm new to the PDDR board and relatively new to the hobby, but I feel I can help with this particular topic. I am a Research and Development Chemist at a large paint company that specializes in aerosols. I apologize in advance for the length of this post.
You DO NOT want to put aerosol cans in hot water. DOT regulations require aerosols to be heated to 130 degrees F prior to shipping, and we frequently have cans that fail (sometimes quite violently) at this temperature. Boiling water is 212 deg F. One of the most common aerosol propellants is a blend of propane (just like for a gas grill) and butane (same as a cigarette lighter). If the can ruptures and and ignition source is present, the result will be a large fireball. I've seen it happen and it isn't pretty. For obvious reasons, dont spray near an open flame, gas furnace or gas water heater. Aerosols can be safely and effectively operated in the range of 60-90 deg F, with 70 deg being the 'ideal' temp. Temperatures slightly outside this range may cause problems, but nothing extremely serious (orange peel or other cosmetic issues).
The aerosol can temperature actually has far less to do with the finished film than you would think, and is going to mostly affect the way the can sprays (higher temp = faster spray rate). Atmospheric conditions and the temperature (and heat capacity) of the work surface play a much bigger role. Humidity is your biggest enemy. Spraying when the relative humidity is over 50% can cause the finished film to be cloudy if the paint is not formulated for higher humidity application. As the paint dries, the evaporating solvent causes the surface to cool, which condenses water out of the atmosphere (just like a cold can of beer on a humid summer day). This is referred to as 'blushing' in the paint industry. Since wood has a poor heat capacity, heating the car probably will do little to help this since the heat will not be retained very long. Spraying at or around room temperature, in a low humidity environment should be your goal. If this isnt possible (I live in WI so my garage is 40 degrees right now), there is a way to fix any blushing that may result. Spraying the car after it has dried with 'Edge Blender' should fix the cloudiness. Edge blender usually contains slow evaporating solvents like proplyene glycol monomethyl ether acetate (CAS# 108-65-6), which will redissolve the paint and allow it to dry in a way that eliminates the blushing. Spraying with a properly formulated clear should also eliminate the blushing. Cheap paint often is not formulated to address this problem. I typically spray my cars in my garage, allow them to dry in my basement, then do a final coat of clear (that contains a large amount of the solvent mentioned above) in my basement to eliminate the blushing.
The painting procedure that I follow and would recommend would be:
1) Optional: an acrylic wood sanding sealer. Pine is extremely porous, so this would help reduce the amount of paint soaked up by the body.
2) 2-5 coats of acrylic lacquer sandable primer (available at auto parts stores). Follow can directions (allow to dry between coats) and also sand with 400 grit between coats. I usually end up sanding the first two coats almost completely off, allowing the primer to fill the small low spots in the body.
3) 2-3 coats of acrylic lacquer 'color'. Again allowing the car to dry between coats and lightly sanding with 400 grit between coats.
4) 3+ coats of acrylic lacquer clear. I let each coat dry and sand with 800 grit between coats. I usually end up putting 6-8 coats on to obtain more visual depth in the paint.
I weighed my last car before/after and the entire paint job only added 3.3 grams.
I recommend acrylic lacquer as opposed to enamel due to its fast dry time and ability to be sanded. Many enamels use resins that take a long time to dry and do not sand well. Some enamels can be dry to the touch in 30 minutes, but you will still be able to leave an impression with your fingernail several days later. Enamels often have spray directions that state that the paint must be recoated within a certain period of time, whereas lacquers are recoatable any time. Remember, less is more. Many light coats are better than one heavy coat. Apply just enough to wet the surface, but not so much that it pools.
Due to the fact that I work at an aerosol company, I do not want to recommend certain brands over others, since I have a vested interest in your purchase, but hopefully these broad generalizations will assist in your paint purchases and application technique.
I'm happy to answer any more detailed questions you may have about aerosols.
WOW! That is great info. Thanks for your input. Welcome to PDDR, you'll love racing here. Its good to see a fellow Wisconsinite on the board - what part of the state are you in? I'm in the Town of Vernon (Mukwonago area) - about 20 minutes south west of Milwaukee.
The only bad news for you is that The Block is not allowed to be sold to anyone else in Wisconsin beside me...............just kidding.
Send those cars in and have fun.