[brainsboy]

Duponts 7900-s Chrome clear
Nasan Base coat
Temp 67
Hardner medium

I have painted several cars which came out close to perfect, sometimes a run here or there. Last paint job I did was 4 years ago or so, and seems I have forgotten alot of what i used to know. Im getting ready to paint my car and started it but ran into a few problems. First let me say the body work is perfect as far as prep work and bondo work. I only used USB bc/cc bondo where needed, and all urethane primer. Car was stick sanded several times final one was wet sanded with 600. Im using basecoat / clearcoat, Nasan base with duponts 7900 chrome clear. Im using the same gun i have always used so I know it well. The base coat go's on beautiful. My problem is with the clear. I'm spraying 1 part at a time, 1st coat is light i spray the edges then the main part, this coat doesnt get a perfect coating its little on the light side, maybe a little fisheye looking, so far so good, or exceptable for me. I wait untill its touchable but sticky, spray a heavy 2nd coat, so it looks like glass no fisheyes, looks great, let it wait little bit, then spray the second coat heavy. All is ok im done with two coats, the next day I get up and all the paint it full of 10 godzillion little pinhole looking holes, They do wet sand out after hours of wetsanding but by the time you wet sand enough off you have gotten down to base on some spots close to edges. Whats causing this?
Problem two spraying another part, thought the pinholes might be from water in the line so I bought a 100$ toilet paper filter, base coat came out beautiful, didnt want the same problem so let it dry over night (thinking I sprayed too soon), cleared it the next day, clear beaded up, got pissed and cussed, started over, sprayed base, waited 1 hour till looked dry, sprayed clear, 1st coat perfect and light not heavy, sprayed second coat perfect no pinholes!, came back to check on it 15 min later, damn thing started webbing in spots, looked like the cow stomach stuff in the food section, let it dry for 1 day, wet sanded with 1000, and buffed it out and you cant see the webbing that happen.
Ok I know im doing somehting wrong, just not sure what it is. Can someone suggest a general procedure to follow for times, and temps.

thanks

[bloverby]

Sounds like solvent pop to me.

[evilone]

same here....hope you get it fixed

[roger1]

It's solvent pop and it's a real PITA!

Get your magnifying glass out. You'll need it to make sure you have sanded it all out because it will show after another coat if you don't.

Roger

[boatbob2]

hi guys,ive painted a number of yachts and cars and i am not familiar with the term SOLVENT POP,can someone explain it to me?also does it only happen with bc/cc? also tell me how to avoid it ..i havent sprayed bc/cc yet,but im going to spray my 48 ford coupe..thanks.

[roger1]

Originally Posted by boatbob2

hi guys,ive painted a number of yachts and cars and i am not familiar with the term SOLVENT POP,can someone explain it to me?also does it only happen with bc/cc? also tell me how to avoid it ..i havent sprayed bc/cc yet,but im going to spray my 48 ford coupe..thanks.

Click on the link that bloverby provided.

[gdroze]

yep solvent pop

[mrcleanr6]

Originally Posted by boatbob2

hi guys,ive painted a number of yachts and cars and i am not familiar with the term SOLVENT POP,can someone explain it to me?also does it only happen with bc/cc? also tell me how to avoid it ..i havent sprayed bc/cc yet,but im going to spray my 48 ford coupe..thanks.

bob. in the marine industry its called porosity. you might be familiar with that!!

[baddbob]

Originally Posted by brainsboy

Duponts 7900-s Chrome clear
Nasan Base coat
Temp 67
Hardner medium

Im using the same gun i have always used so I know it well. The base coat go's on beautiful. My problem is with the clear. I'm spraying 1 part at a time, 1st coat is light i spray the edges then the main part, this coat doesnt get a perfect coating its little on the light side, maybe a little fisheye looking, so far so good, or exceptable for me. I wait untill its touchable but sticky, spray a heavy 2nd coat, so it looks like glass no fisheyes, looks great, let it wait little bit, then spray the second coat heavy. All is ok im done with two coats, the next day I get up and all the paint it full of 10 godzillion little pinhole looking holes,

base coat came out beautiful, didnt want the same problem so let it dry over night (thinking I sprayed too soon), cleared it the next day, clear beaded up, got pissed and cussed, started over, sprayed base, waited 1 hour till looked dry, sprayed clear, 1st coat perfect and light not heavy, sprayed second coat perfect no pinholes!, came back to check on it 15 min later, damn thing started webbing in spots, looked like the cow stomach stuff in the food section, let it dry for 1 day, wet sanded with 1000, and buffed it out and you cant see the webbing that happen.

thanks

I read the post and a few things come to mind as possible causes, Just guessing but are you spraying with a conventional gun- what model? What air pressures?

The 7900 clear is a high solids clear that requires some really good atomization to get it on right, the fisheye looking first coat indicates the material isn't getting atomizes well enough. When this happens a person usually tends to put more clear on in order to get a smooth surface and this leads to some major buildup fast which then leads to solvent trapping if the surface doesn't stay open/wet long enough to let the solvents come out. I'd suggest shooting a few test panels in order to get your setup right before you try painting the parts again. Try cranking your air pressure up some to get the clear atomized or try a different gun. The webbing is from applying base then clear then base then clear when all is fresh, what is happening is the second application of base wrinkled the clear below it, this can happen after you clear trapping solvents below. Hope I made sense.Bob

[Bee4Me]

What Bob said and the temp your shooting at is VERY borderline.
That clear is probbly really thick at that temp plus the parts themselves are cold too compounding the problem. Your obviously bombing on too much product trying to get it "right" and the solvent is really taking a toll on the job.
It's time to take a break and regroup and get some place warmer to shoot.
As for "recommended" flash time,you can throw that out the window. It could take 1/2-1 hr. between coats at that temp. I'd wait till it's basically touchable before applying another coat.

[brainsboy]

Thats exactly what im doing, I forgot who makes the gun I want to say "sharp", but it has a 1.4 or 1.5 tip going off memory, anyhow the droplets when i spray are huge, more like the size of a pen tip. So I'm probably spraying too much clear to make it smooth out. Thanks I will try some test parts, and get the temp up to 70's.. Ohh I was using 25psi in a gravity feed gun.

[BarryK]

Need to check out the gun, if you have had it a long time it may not be an HVLP and if thats the case your going to need 40-55 lbs to get the 7900 through a sharp. 1.4.

Also just to be honest with you if it is a Sharpe HVLP, your going to have a hard time shooting that clear anyway, so start with the air in the 30's and adjust up as needed just to start overriding.

How did the gun lay the base?
Color of base?
How many coats of base?
How long did you let the first coat of base flash as thats more important than letting set overnight depending on number of coats and color.
Also did you use a sealer, 2part or one part?
Are you sure you can wet sand the primer you used?

From what you described, your solvents are coming from deep, could be first coat of clear, base, sealer or primer.
If first coat of clear, the second coat will usually blow up in seconds or a couple of minutes.

Can't answer till we have other facts.

[gdroze]

hey what temp reducer are you using for the base .and what temp reducer are you using for the clear .also what mixing ratio are you using for the clear

[crashtech]

Originally Posted by Bee4Me

...It's time to take a break and regroup and get some place warmer to shoot....

Amen to that! Though in my case, I'd need about a 6 MONTH break every year if I couldn't paint below 65 or so!

My theory is that these higher solids clears are hard for people to handle. I remember when I first started shooting them in the early 90's and found my spray technique lacking. (I still find it lacking, lol!)

If the mfr. allows it, a little extra reducer in the clear can go a long way to help sprayability, especially with a gun that isn't so good.

[BondoKing]

you may want to check out this link... I think it may be of interest to you
good read