Difference between Priming and Sealing? - Exterior Forum

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Difference between Priming and Sealing?
Sunday, September 04, 2005 12:03 AM
Read the Exterior FAQ have a few questions for painting regarding the following:

Primer then Sealing

"When to use primer or sealer:
If you have filler, factory primer and/or bare metal to cover use primer.
If you are covering old paint use primer/sealer."

1. What do you does it mean to seal the primer before putting a base coat?

2. If I were to change the entire color of a car, would I go an sand the body, and prime it, and sand some more, and then "seal" it before I put a few base coats and then clear coat?

i am a complete novice to auto body painting but i wanna do it for my car to well say "i did the painting and body work, and yes, I learned another trade while customizing my car".

any suggestions, faq, or info would be very helpful and benificial.

Re: Difference between Priming and Sealing?
Sunday, September 04, 2005 12:10 AM
well sealing means that it fill all the small pen holes or even primer spots so the seal can get the base coat a better holding while drying.and if you wanted to change the whole color of the car you would have to sand all the old paint off and use body filler to fill in holes,deep sanding marks or other problems you have and before you paint it you got to put couple layers of primer and you gotta wet sand the primer before you put the sealer on it before painting the car.


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Re: Difference between Priming and Sealing?
Sunday, September 04, 2005 12:15 AM
and i wanna add little bit more on the purpose for the primer 1.) it gives better adhesion 2.) gives better filler 3) its easier to sand


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Re: Difference between Priming and Sealing?
Sunday, September 04, 2005 12:18 AM
sounds like a lot of prep time and work... all worth it.. and im going to do it.. lol

anyone else have anything else to add?

is there a more extensive paint/exterior faw somewhere on the site?
Re: Difference between Priming and Sealing?
Sunday, September 04, 2005 6:05 AM
Yeah actually... (I just woke up so bear with me)

Unless you have little dings and stuff on your car... you do NOT need to use body filler when you sand your car down to metal... or near metal.

Primer will fill the scratches left by sanding the paint off.

There's different ways of doing it... but for someone with little experience here's what I would do:

(actually... before doing any of this I'd wash your car, then clean your car with some wax and grease remover... which can be purchased from an auto paint supplier)

1. Sand down the paint with 180 grit... getting as close to the metal as possible.

2. Prime (I'd say 2 to 3 coats), recommend a self etching primer. Let sit overnight (follow the directions on teh back of the primer container. NEVER USE spray bomb!) Make sure you have a cup to mix the primer in and follow the mix ratios on the can.

3. Block sand it with 320 or wet sand with 400, then 600. You don't want to use a finer grit than that really because it will or at least COULD interfere with the adhesion of the paint.

3 1/2. Clean down the car again with the wax and grease remover, and use a tack cloth to remove and dirt

4. Use a sealer, follow the directions on the back of the container... and the mix ratios on the can. Wait for the recommended period of time

5. Then paint. I would put the first coat or two on dry, then medium coats after that... until your area is evenly covered.

Now... the tricky part about painting... (none of this is quite as easy as it may sound).

When you're painting, you need to know what psi to have your gun at (most are around 45 psi)... use something (like a box or something) to hold your gun up to, to adjust your fan pattern and material feed.

Invest in a good gun... gravity feed HVLP guns are the best (High Volume Low Pressure)... I'd recommend a Sata or Iwata.

With most base coats... you're going to use a 50% overlap pattern to spray. With metallics and pearls... you need to alternate your spray pattern to get an even coat and not have the metallics or pearls "stripe" on you. i.e. spray first left to right, up and down, diagonally both directions.

Clear is a little tricky for someone who's never sprayed before... and something we can't really help you with over the internet. (i.e. knowing what to look for). You don't want your clear to look "bumpy"... or dry... but you don't want to put on too much... cause the clear will run or sag. Which isn't a big deal... it'll just need wet sanded and buffed to get out any dirt or runs or sags.

DO NOT sand your base coat... especially if it has metallics. Some people say to do this... I HIGHLY do not recommend it.

I think that is all for now...




Re: Difference between Priming and Sealing?
Sunday, September 04, 2005 6:58 AM
that was good ya beat me to it
a high build primer filler is made to fill any imperfections that an area might have to a certain degree, I.E. ppg`s ncp 271 is a high build corrsion resistant primer
and in the dbc system ppg`s sealer is not crrsion resistant so they have a self etching primer goes on before the sealer sealer is made to coat the body work before base coat it will fill scratches like 600 and 400 and 1,000 sealer is not made to be sanded down DO NOT SAND THE SEALER

first thing i would do id tear the car apart that`s obvious, i would also invest in a good D.A. and a mud hog the 9 inch d.a. i personaly would mud hog the car with 80 then finish it up with 180 that`s just me
fik dents fix rust if any prime let that sit for i say 3 days dry block with 120 or 150 re prime then wet sand with 320 then 400 then 600 then with a red scuff pad to get the shinny spots ya missed
agreed sata!!! her and i can not tell ya how to paint online just ain`t goona happen sorry
i think that`s about it


can i haz bondo
Re: Difference between Priming and Sealing?
Sunday, September 04, 2005 8:24 AM
big daddy> thanks for touching up on some of the spots I forgot to mention... like not sanding the sealer lol.

Also... if there are areas you NEED to sand by hand that you cannot get a DA or mudhog or block into... USE YOUR PALM NOT YOUR FINGERS!!! If it's a REALLY tight area... you can use your fingertips if you need to... just DO NOT dig into it. Every spot needs sanded... or the paint will not stick.




Re: Difference between Priming and Sealing?
Sunday, September 04, 2005 10:26 AM
correct
or use a flexable block and sand it with that
remember kidies if u sand with your fingers it leaves lines and waves
use a block


can i haz bondo
Re: Difference between Priming and Sealing?
Sunday, September 04, 2005 12:31 PM
you still would have to use body filler to fill in the sanding marks.


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Re: Difference between Priming and Sealing?
Sunday, September 04, 2005 4:49 PM
Xtreme97Sunfire wrote:you still would have to use body filler to fill in the sanding marks.


No you don't. That's what the primer is for... high build primer for deeper marks... body filler is used for body work... not sanding. If you have a dent, after you've pulled it, you use body filler to "fine tune" it. Small dings... glazing putty/ezsand/icing is usually recommended...

BODY FILLER IS NOT FOR SANDING MARKS... unless you're an idiot and used a grinder to take off your paint...

I am an auto body tech/painter... I do know what I'm talking about...




Re: Difference between Priming and Sealing?
Tuesday, September 06, 2005 6:17 AM
Fallen Angel
- what are you opinions on a good quality gun .. i was thinking about getting devilbiss Finishline 3 ® - HVLP ... is this a good gun?

I dont want to spend too much but i also dont want to sacrifice too much quality.. which is hard to get these days but any suggestions would be great.

thanks.. also what do you suggest for nozzle size for base/clear .. i got a few cheaper guns i use for priming and stuff.

thanks


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Re: Difference between Priming and Sealing?
Tuesday, September 06, 2005 3:43 PM
I would look into Sata or Iwatas for paint guns... they do have some cheaper stuff... but they're the best that's out there.

Just remember...

A bad gun in the hand of a bad painter... is going to give you HORRIBLE results...
A bad gun in the hand of a good painter... is going to give you meh results
A good gun in the hand of a bad painter... will give you better than horrible results...
A good gun in the hand of a good painter... will give you a beyoootiful paint job!!!

You can only paint as good as your gun is...




Re: Difference between Priming and Sealing?
Tuesday, September 06, 2005 3:58 PM
SATA!!!
and she is right ya beat me to it


can i haz bondo
Re: Difference between Priming and Sealing?
Tuesday, September 06, 2005 5:41 PM
big daddy wrote:SATA!!!
and she is right ya beat me to it


Well we're a team right? lol. Gotta help out the fellow JBO members!




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