Painting questions

W

wrndln

Well-known member
I hate to be asking so many painting questions, but I want to do it right. I have the product information sheets for all the paint products I am using like DPxx, K36, Concept and DX685. The first question I have is: Can Concept be applied over K36? I have read in the product information that it can, but I also read that it should be sealed with DPxx. The problem I see with sealing the car with DPxx (thinned) is that it will probably have some imperfections with the DPxx coat that might show through the Concept. If I were to spray over will sanded K36, I know the surface would be very smooth. I have sealed the car a couple of times in the process of sanding out the scratches and imperfections. The K36 is 98% intact with only a very little DPxx showing through. The last question is: Is it OK to scuff or lightly sand DPxx within the 7 day curing window before applying a top coat of Concept. I know DPxx is not a sanding primer, but I think I have some places that need a little "smoothing" before the topcoat is applied. Thanks for any help with these two questions.
 
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Whew, --bless your heart as I know you are trying hard, ...and you have all the good intentions but it kinda seems like someone has sent you down the wrong road without a map. I know I can't tell you everything you need to know but lets hit the high spots and go from there.......

You can apply DCC over bare metal if you like. Technology has changed with plastic urethane paints where the primers are actually surfacers and used for leveling and not speecifically for adhesion. Therefore you can actually spray over clean, bare metal with great results. Just remember that anything you apply it over just needs to be able to have enough 'tooth' (scratches) for it to bond to.

My question back is why do you feel the need for a sealer? What base are you applying it over that needs to be sealed? IMO you are wasting money and causing unnecessary mil build-up.

Again, why are you using an epoxy primer as a surfacer? Epoxy paints are more about corrosion prevention, --and not as a sanding surfacer used for leveling. IMO you should be using a MP product such as MP282. You can scuff off the epoxy within the 7 days but it will not sand well (as it likes to ball-up).

With regard to using 685, you need to do some spray-out test panels first for test purposes. You did not mention which color you are wanting to spray but how wet the coats are when applied dictates the flatness, ...as does the pigments inside the main color. Also, which hardener you use with the DCC also changes the gloss intensity.

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About the issue of spots where you sanded all the way through your K36 down to DP primer underneath it: If there is a color contrast (e.g. you used black DP primer) it might tend to show through the color coat. It depends on what color you are using. On my car I used a black DP sealer coat over the K36. There were a couple of tiny spots (1/2" on a side) that I missed when spraying the sealer coat, where the light gray K36 showed. A spot of K36 could still be seen under the first coat of maroon paint, but under black paint, it was hidden immediately.
 
Rusty,

As you know I am an amateur at this painting business and thus you should value my advice accordingly. One of the biggest frustrations I had with the painting experience was trying to use the 685 to reduce the gloss. Perhaps it was because I was painting different pieces at different times. I found it impossible to replicate and I was extremely careful in ensuring that my mixtures were identical and used a paint shaker to ensure uniformity.

In the end here is what I did and wish someone had told me this advice before I started. The first piece of advice I think I did pick up from a "Brent Post" several years ago (paint the surface using gloss first).

First any surface I wanted flat I painted it with gloss first (I used Concept). I would then sand that surface using 600 grit. By using the gloss I was able to get uniform coverage. I then would buy the same paint/color from the paint supplier mixed with an eggshell level of gloss. This worked every time. I realize that he was probably using 685 to reduce the gloss and cannot explain why using the premixed gave me consistent results - but it did.

Good luck Rusty

Hunter
 
You do not under any circumstances put DCC over bare metal!
I am a PPG certified tech with over 25 years experience with painting cars and equipment. I believe in following the tech sheets and doing things properly to greatly reduce your chances of problems.
If you have applied epoxy as your initial layer over the bare metal and followed it with K36 surfacer, you have a good start.
I'm assuming you have a typo and meant "well" sanded K36.
If you have a few areas where the epoxy is showing thru from sanding the K36, you could go directly to DCC without sealing. However, if there is any bare metal showing you need to prime those spots. A good way to do this is to use the epoxy as a sealer. Remember that even if you don't see bare metal you may have a spot of epoxy that is too thin so I advise to use a sealer every time. Sealer gives you a consistant surface for the color. Usually for single stage, if you have color variations from dark and light spots because you didn't seal it means you did not apply enough color.


An issue I see with your post is your fear of getting imperfections in the sealer. If you have concerns about dirt in the sealer, how are you going to spray the color without imperfections? It's good to ask the question as a "what if" , but go into with a positive attitude that you can spray the sealer with no errors.
Yes, you can scuff some imperfections in the epoxy sealer. Do not sand too much and make it thin. ScotchBrite won't level, only scratch. Use sandpaper to remove the imperfection (the one you're not going to get!).
I wouldn't push the 7 day window, get on it later that day or the next morning.
 
Take this for whats its worth since I am no expert and just started my painting (fenders are done) but I am following a similar process to yours. I used DP primer over the bare steel, I used DP because I used rust converter in some of the pits and also wanted to shoot over the lacquer in the interior. Then I used K38, almost same as k36, just higher build I believe. After blocking and sanding I too burned through in a few spots and made some more filler repairs so I re-shot k38 on the really bad panels and sanded to 400. I had planned to shoot DP as a sealer over the K38 but hated how it sprayed originally and left a rippled finish. Supposedly reducing will help with this but I was still leery and wanted to shoot right over the K38 to avoid an extra layer.
Problem is i'm using DBC bc/cc and according to the P-sheets it MUST be sealed before applying BLACK. however looking at the sheet I see no mention of that for DCC so you may be OK with just the K36.
Luckily my rep I have been buying paint through has been super helpful and actually paints rather then just sell paint. He recommended I seal before BC and to use the NCS2005 sealer rather then DP since DP would need longer to flash and would be more likely to trap solvents. The NCS laid down flat as glass, also helped hide many of the problem areas I was concerned about and was much cheaper then DP. I immediately followed up with my base and clear.
From what I understand after reading numerous posts and tech sheets the main reason to seal before BC is because the mechanical adhesion of Black basecoat is unreliable and needs a wet catalyst below it to stick. With the single stage DCC the catalyst is actually in the paint so as brent pointed out above you really should not need a wet coat of sealer below but again take my advice with a grain of salt. Up till last weekend I had no business commenting on paint (and still don't) but wanted you to know your not alone in your dilemma.

Bob, NJ
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RTC1930 said:
Take this for whats its worth since I am no expert and just started my painting (fenders are done) but I am following a similar process to yours. I used DP primer over the bare steel, I used DP because I used rust converter in some of the pits and also wanted to shoot over the lacquer in the interior. Then I used K38, almost same as k36, just higher build I believe. After blocking and sanding I too burned through in a few spots and made some more filler repairs so I re-shot k38 on the really bad panels and sanded to 400. I had planned to shoot DP as a sealer over the K38 but hated how it sprayed originally and left a rippled finish. Supposedly reducing will help with this but I was still leery and wanted to shoot right over the K38 to avoid an extra layer.
Problem is i'm using DBC bc/cc and according to the P-sheets it MUST be sealed before applying BLACK. however looking at the sheet I see no mention of that for DCC so you may be OK with just the K36.
Luckily my rep I have been buying paint through has been super helpful and actually paints rather then just sell paint. He recommended I seal before BC and to use the NCS2005 sealer rather then DP since DP would need longer to flash and would be more likely to trap solvents. The NCS laid down flat as glass, also helped hide many of the problem areas I was concerned about and was much cheaper then DP. I immediately followed up with my base and clear.
From what I understand after reading numerous posts and tech sheets the main reason to seal before BC is because the mechanical adhesion of Black basecoat is unreliable and needs a wet catalyst below it to stick. With the single stage DCC the catalyst is actually in the paint so as brent pointed out above you really should not need a wet coat of sealer below but again take my advice with a grain of salt. Up till last weekend I had no business commenting on paint (and still don't) but wanted you to know your not alone in your dilemma.

Bob, NJ
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Click to expand...

I see no problems in what you posted, seems correct, I just prefer to seal everything because of the reasons I posted above. I've painted plenty of times back in the day without sealer, seem to have less problems now with it.
I am not a fan of epoxy as a sealer, and yes it must be reduced to use it as a sealer. I use K36 mixed as a sealer or mainly 3025 sealer. Alot of DIYers like epoxy as a sealer since they already have it as their initial primer and don't have to buy additional products.

Your fender look good from here!
 
Brent,
This is the first car I have painted, so I am sure I have made some mistakes and probably some overkill in some areas. I want to do it right after all the work I have done welding in patch panels, taking out dents, find original parts that were to far gone or hacked up but the previous owner(s) to repair, etc. One mistake I know I made is to not use finer sandpaper like 150 or 180 grit after getting the filler contouring done with the 80-grit sandpaper. That would make many of the 80 grit scratches disappear before the final paint preparation work.

I am using Concept with DCX61 catalyst and DP870 for reducer. I want to paint some areas, like the firewall, rear fender wells, door jambs, inside portions of the hood panels, trunk lid and doors with flattened Concept. I have painted the inside of the car (28 special coupe) some time ago with DX685 flattened Concept with good results. I used a ratio of 22 oz DX685 to 32 oz of Concept like the product sheets state for a semi-gloss sheen and it turned out to be the right satin finish I wanted. I want to do the same on the items I mentioned above, so I was going to use the same ratio. I can test the flatness (spray out) like you said, but as long as it is satiny, not glossy, I would be satisfied. The main question I had was painting over K36. I think you stated that was OK. Almost everyone I talked to said they "seal" the sheetmetal with DPxx before the final top coats. I am using 320 grit wet sanding to smooth the K36 and give it some "tooth", like you mentioned. Before all this, I sealed the sheetmetal with DP50 and 2 or 3 coats of K36. I then sanded the K36 down to where I could see much of the DP50. I did this because I could see sand scratches from the 80 grit I used to form the filler - Rage Gold. I then applied a sealer coat of DP50 and 2 coats of K36. That is where I am now. I am now sanding the K36 smooth to ready it for three coats of Concept. I plan to spray 3 coats of Concept on the body and the other pieces so I can color sand it with less likely hood of sanding through the paint.

Thanks for you comments and help. I need all the help I can get.
Rusty Nelson
 
Thanks to all that have posted responses to my original post. I think I have a better understanding of what to do and not do. I think I sanded all the 80 grit sandpaper scratches out when I sanded the two or three coats of K36 almost down to the DP50 epoxy. In the next few days, I see if it all works out.
 
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