Degassing Paint

I'm sure this topic has been discussed before, but it's something I never gave much thought to? For me I would prime my rocket. Wait the next day or even he same day after the primer has dried and then spray my top coat ...

So why is it necessary to allow the primer to "Degas" (sp) before spraying the top coat and how long should you actually wait?

Does this rule apply for top coats as well such as your enamels and lacquers?

Are all primers same? I mostly used the HBP from Duplicolor and Rustoleum.

I use a primer that is thinned with acrylic laquor thinner, its painted on, and dries almost instantly. if i get carried away, and it gets thick, it can take up to an hour or so...
then it sands off.... with a breeze..
Once its sandable, you can paint over it...
your just waiting for the laquor thinner to evaporate... (really wont harm a top coat if its not done...)

I love this stuff, 13.00 a quart or 45ish for a gallon..

https://www.raj.co.nz/sds_pdfs/transtar/tech_data_sheets/Transtar_TDS_6001_Universal_1K_Primer.pdf

It is my understanding that all spray paints and primers outgas during the curing process. This is why they list recoat times on the can. My suggestion is to stay well within the recoat times for same coat or wait for a significant time outside the recoat time to add additional colors and masking.

great advice guys thank you.

I was just curious about the topic?

El Cheapo is Right on:
All Paints and primers outgas as mentioned. The Reducers, thinners and vehicles used dissipate at different rates. As ClayD mentioned Lacquer thinner reduced paints and primers outgas much more quickly then Miniral Spirits, Terps or many of the enamel reducers, and explains why water based acrylics seem to take forever to dry... Humidity plays a HUGE part in this process as will.

All the chemistry aside one of the easiest ways to determine if your last coat is ready for the next step is to Closely follow the Recoat times listed on each and every can of paint.

Always use the sniff test before mixing paints and/or primers. That is with you nose placed ON the painted surface if you can smell ANYTHING it is NOT dry or cured. This can be very helpful when mixing brands of Primer and paint. a sure way to lift the previous layer is to NOT have allow the first to have completely outgased.
Hope this helps.

Side note on clear coat...For whatever reason, clear coats cure much faster than paint. The result of this is they generate an enormous amount of heat during this process compared to paint.

When using clear, your paint surface needs to be completely cured. Not hours or days but a good week or more to be completely safe depending on weather, humidity, etc. Spray many, many light coats. We're talking mist here. If in the first few coats it looks wet, you are spraying too heavy. When a thick coat of clear starts to kick, just like resin, it gets extremely hot and WILL kraze or krackle your base coats. Once you do that, it's all over but the cryin'.

Clear coat is great but care and diligence must be taken. Be patient with it and it'll treat you right. Rush a clear and it'll screw you every time.

Good luck

El Cheapo said:

Side note on clear coat...For whatever reason, clear coats cure much faster than paint. The result of this is they generate an enormous amount of heat during this process compared to paint.

When using clear, your paint surface needs to be completely cured. Not hours or days but a good week or more to be completely safe depending on weather, humidity, etc. Spray many, many light coats. We're talking mist here. If in the first few coats it looks wet, you are spraying too heavy. When a thick coat of clear starts to kick, just like resin, it gets extremely hot and WILL kraze or krackle your base coats. Once you do that, it's all over but the cryin'.

Clear coat is great but care and diligence must be taken. Be patient with it and it'll treat you right. Rush a clear and it'll screw you every time.

Good luck

Click to expand...

Would it be safe to assume that if you spray clear over a white top coat and it "yellows" the coat has been applied too heavy?

I would say you used an old can of clear or a cheap can without any UV protection. I know the pain. That sucks.

El Cheapo said:

Side note on clear coat...For whatever reason, clear coats cure much faster than paint. The result of this is they generate an enormous amount of heat during this process compared to paint.

Click to expand...

Nice observation but I dont know if that is 100% true. I don't know what type of paint(s) you use or how you spray them so it may be different from my experience and I can only speak from my experience. I know when I use my nice paint (house of kolor) for a model I can spray a coat or two and let it dry over night. The bottle says a week for full cure time. Then i use Dupont 4 to 1 snap dry clear coat, and that clear takes a few months to fully cure. That is or is similar to the same clear used on cars and that's why you are not supposed to wax a freshly painted car for a few months, because it takes a few months for it to degas.

If you find an MSDS sheet or something for your clear it generally tell you dry to touch time as well as when you can wax it.

You use the spendy stuff. For us Cheapos, my info came from a friendly Rustoleum Customer Service Rep.

Yeah, but I only use it on a few projects every once and awhile. In the model making program we have to do all steps including paint so I generally have a wide variety of paint to choose from. TCP global sells 2 and 4 oz house of kolor paints for like $6-$10 and can be combined with a cheap airbrush that has a huge spray pattern to spray rockets.

But hey, learned something new about rustoleum

Thats why we come here, to learn and pass on what we know. I have no experience with air guns. I'm guessing my info applies to pretty much anything in a can as that has been my experience with Rusto, Krylon and Walmart brand. As far as I know, the WM brand does not have any UV protection so I would stay away from it unless its stated on the can.

Mr Bigmouth [me] has to put in his 2 cents: The propellent in an aerosol paint can not only provides the transport of the paint from the can, it also keeps the paint liquified in solution, allowing it to pass through the tiny nozzle. The propellent is very volatile, and it begins to volatize once it leaves the high pressure of the can. By not waiting for the paint to cure fully, that propellent is still working to keep the paint "liquified", and so the paint still behaves plastically. Once the propellent is completely "evaporated", the paint is "dry" and rigid, adhering (hopefully) to the painting surface. THAT"S WAY MORE info than you wanted, I'm sure.

"Mr. Bigmouth" sounds like a good name for a rocket.

Micromeister said:

Always use the sniff test before mixing paints and/or primers. That is with you nose placed ON the painted surface if you can smell ANYTHING it is NOT dry or cured. This can be very helpful when mixing brands of Primer and paint. a sure way to lift the previous layer is to NOT have allow the first to have completely outgased.
Hope this helps.

Click to expand...

If you don't feel like dying from huffing paint you can always put a little bit of water on it to see if it has "legging". You may need to lightly sand your primer, but if the water starts "legging" then your solvent is not fully dissolved.

And paint can be dry before it has degassed. If you spray nice primer (automotive, sparvar, plastikote etc) it should dry in like a minute, but it doesn't degas nearly that fast.

I strongly advise testing paint (this includes the priming step as well) before you paint the next coat. If the solvent hasn't degassed it can go up into the next layer etc etc and make you paint take ages to dry. This is especially true when you mix paint types. If you spray a coat of paint, let it dry and not fully degas, and spray different paint on top of that it will cause major problems. The solvent will get out of that first paint layer and go into the second layer, and if the solvents aren't the same it can make your paint get real bad real fast