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Old 08-08-2004, 01:13 AM
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Unhappy sanding ppg dbc basecaot to recaot

i am using ppg dbc deltron 2000 and i was told to wait five days then sand my base caot then apply 2 to 3 more caots of base then my tri caot then clear because i didn't use primer sealer . i would like to know what the reason for sanding my base caot . someone told me it is because it will give it a uniform finish and get out any scratches out before i clear it , is this true or am i just wasting time & money . if i should sand it is finer grit sandpaper better, like 800 grit or should i use what the tech sheet says,400 to 600 wet & dry .

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Old 08-08-2004, 09:20 AM
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This perhaps was a waste of time.
Now you must sand the base as it re-coat time is up for good adhesion.
I would use 600-1000 wet and although not necessary I would put one more coat of the same color over it before you continue,
In custom work sometimes we let the first two coats of base set overnight and wet-sand just for the added amount of slickness or for flaws.
After this if you want overkill, if tech sheets say wait 30 minutes between coats, wait 60 and same before applying clear for more clarity maybe first coat of clear is not shot for 2-4 hours.
Personally I will let base set over night on some jobs before applying clear, 12 hours is easily in side the adhesion window with most bases.
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Old 08-08-2004, 12:50 PM
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This would not have been necessary, but it will remove any dirt nibs or sand-scratches you have. Sand it with 600-1000 grit, just as Barry has stated, but you will HAVE to re-coat with base, or it will show the fine grit scratches. In other words, it'll look just like it's been sanded, only shiny!!
Apply two coats of base allowing flash times and allow the base to become fully dull before starting the mid coat. It's a good idea to tack the entire car again too before applying the mid coat. Go over the entire vehicle twice with a good tack rag, making sure to get all the masked areas as well, not just the painted surface. Just make sure all the loose particles from the base coat is removed before proceeding to the mid coat. Having to fix a problem in the middle of a tri coat job is never fun. It can be done, but if something happens in the middle of the job, you have to go back to the base, blend it, carefully blend in the mid coat and so on. It's a pain, so make every attempt to keep it clean, and paint like a robot.
Every move should be well rehearsed by this point, as you should apply your primer just as you would the mid coat, getting used to each move you're going to make when the time comes to spray the candy, pearl, or whatever you're putting down as a mid coat. Walk the entire length of the car, spray evenly, keeping the gun distance from the panel consistent and overlap each successive coat by 75%. If it's candy mid coat you're spraying, over reduce the first coat or two just slightly, as this will bring the color in slower, but more uniform. Again, paint like a robot. Very precise, straight lines is the key to successful tri coat painting. Imagine the car as a perfect rectangle, and don't get tripped up by following body lines.
Tri coats aren't hard to paint. It's the stubbornness of some painters that make an otherwise beautiful, successful tri coat job look like crap. Stopping at panel edges is a common practice among painters. You've seen the guys, when doing an overall paint job, they'll shoot the front fender, move a couple feet, shoot the door, move on down, get the quarter and so on. If you do this, STOP!!! It will not work on tri coat paint jobs. I know of two cars, owned by the same guy, who hired different painters, that both turned out this way. They did a good job of getting the paint to lay down nice, but they killed it when they 'panel painted'. You look down the side of the car and see light-dark-light-dark-light. In my opinion, they look horrible. Sadly, both painters SHOULD have known better.

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Old 08-10-2004, 10:43 PM
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thank you guys for taking the time and pointing me in the right direction. i have one more question . the tri caot i'm sparying is prizmatique silver and i was wondering what the best over lap would be 50%,75%or90% and should i dust the last coat on . i was told it will even out the flake so there isn't any lite spots of fake. thanks again for your replys to my post
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Old 08-10-2004, 11:20 PM
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If your spray technique is right, there won't be any light spots to bother with. Are you mixing the Prizmatique with DBC500?? It should spray out very well if that's what you're mixing it in. DBC500 is mixed at a ratio of 1:1 but I normally over-reduce it a bit, mixing it at about 1 part DBC500 to 1.5 parts DT885. It'll spray out flatter, and it dries really quick!
Spray it just like a candy or pearl, with a 75% overlap. I've gotten used to spraying that way, so I overlap everything 75%, sometimes a little more.

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Old 08-15-2004, 05:48 AM
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i've been sanding my base coat so i can apple more base coat and i noticed little shiny needle size craters in my base coat . the only way i noticed it was when i was looking at the surface really close. i can't feel them when i slide my fingers across the surface and i was wondering if i have to sand them all out because i am burning through the base coat alot to get them out and if i don't sand them out will they be seen when the paint job is finished.
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Old 08-15-2004, 06:52 AM
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99 times out of 100 when you see pinhead craters in your base its from the primer.
When you sand the primer is very hard to see these craters and normally don't show up until you apply base.
Two things cause the pinhead size ones in primer,

1st not allowing enough time for flashing between coats or piling on. Piling on a 2K sealer can also do this.

2nd thing that can do this is water in the line.

If as you say you almost have to sand the base off to eliminate
thats a good indication its in the sealer or primer coat.

It would be a rare occurrence that a good base like DBC could do this- water in line but this base is pretty forgiving.

Yes it will show up in clear.
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Old 08-15-2004, 08:17 AM
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if the craters were in the primer ? when i sand throught the base coat to the primer the craters would still be there but with base coat hi-lighting the crater.primer is greyand base is black. this isn't what it looks like it looks like it is in the base. if you spray base coat in your garage at on rainy humid day would that cause this problem or putting the base caot on before the prep sovent dried completly . if is water in line what do i do to stop this. i already bought a sharp wall mount water trap with pressure ragulator+i use a filter at the gun.
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Old 08-15-2004, 09:52 AM
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It is possible the black solvent popped. Black is the slowest drying base because its full of carbon and carbon conduces electricity so its drawing the solvents back in when there trying to get out. Now add rain to the picture or very high humidly and there is less dry air to accept the solvents so it skims and traps the solvent.
The next coat of color now re-flows the black (to a degree) and the solvents start flowing and now the coat your spraying skims and the pinholes start.
HOWEVER the black could have done the same thing to the sealer or primer .
Whatever it was sand them out as the solvent problem is now gone.
Yes wax and grease remover can do this but usually its the very cheaply made ones because they are slower to dry.

A lot of guess work here without seeing it.
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Old 08-15-2004, 11:46 AM
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Something I've been doing for quite some time now when spraying DBC black (DMD1683) is to only reduce it by about 25-50%, as opposed to the suggested 100%, or 1:1 ratio. It covers better and dries faster. The black seems to be dirty paint though. I use the finest strainers I can gt my hands on and I always use two strainers, (I know, I'm nuts) but the black base is always full of dirt nibs. I usually spray two caots, allow time for it to dry fully, light nib sand the surface with 1200, using DX320 to wet the panel, and quickly drying it off before it has time to flash. Then I will come back with one final coat of black. This seems to realy cut down on the dirt nibs in the final paint job. I don't have a problem with dirt in most colors, but black is the worst!

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