Help understanding Perfect Paint Job wet sanding techniques

T

Tuna55

Promoted Users
Hey folks, I think my other attempt to ask this was lost. If it shows up roughly in duplicate, I am sorry.

The truck was done and blocked and in sealer, and I put 3 coats of Motobase base coat on everything (I have a few panels left yet). The surface is pretty good. See (bad) picture attached.
truck parts.jpg


I am assuming wet saning now before clear, at 1500 grit like the perfect paint job recommends. Fine.

When the clear starts, the instructions get confusing. They seem to indicate wet sanding with 800 grit between coats and then nothing on the top coat, is that right? Does that mean that the last clear coat is just buffed? How long after spraying can it be buffed? Why is the wet sanding on clear so much more coarse than the wet sanding for base coat?

Also, I made a temporary booth with a big tent with walls, a box fan taped to a hople in one end, and a shop vac blowing in air through a 4" duct at the top of the other end. It works pretty well. Am I reading correctly that I shut off both inlet and outlet after spraying each coat of clear?
 
You are misunderstanding the perfect paint job on several fronts.

Do not sand base without reapplying more base.

Do not sand clear between coats.

If you want to flow coat then apply 3 or 4 coats, let it cure, block sand it with 800, and then shoot your flow coats. Honestly for what you are doing I’m not sure I see the need for flow coating. I rarely flow coat….

Just turn off your fan and shop vac between coats.

Don
 
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Sanding base coat is just to correct imperfections. Then, as mentioned, add two more coats of base. Let it sit overnight.
Next day, tack it off then decide if you want to apply 4 coats and stop or if you want to do a flow coat, which is 4 more coats. For the flow coat, sand the 4 previous coats of clear coat with 800g and let it sit outside for the day. That will draw all of the previous solvents out. The next day apply the final coats of clear. Then, you can let it sit outside for another day and then begin the sanding of the clear, called color sanding.
 
Flow coat will give more material to work with and a much flatter finish. It's usually done on show cars. Usually, 4 coats is plenty.
 
Since your based panels are sitting outside getting UV exposure (huge no no for base) you’re going to need to sand them and rebase, and get the clear on the very next day.

With the kinds of questions you’re asking, don’t worry about flow coating. Make your goal for this first one just to get it done.
 
Lizer said:
Since your based panels are sitting outside getting UV exposure (huge no no for base) you’re going to need to sand them and rebase, and get the clear on the very next day.

With the kinds of questions you’re asking, don’t worry about flow coating. Make your goal for this first one just to get it done.
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They are not outside.
 
Do you really need the shop vac blowing air in?Would think theres enough leakage around to draw air in?
 
Tungsten said:
Do you really need the shop vac blowing air in?Would think theres enough leakage around to draw air in?
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I felt that a filtered input intententionally was superior to drawing air in from wherever, which could include around the bottom of the tent where debris is. It felt pretty decent in terms of airflow in the tent, from front top to back bottom. Not windy, but moving, and the fog dissipated pretty well.
 
Lizer said:
Since your based panels are sitting outside getting UV exposure (huge no no for base) you’re going to need to sand them and rebase, and get the clear on the very next day.

With the kinds of questions you’re asking, don’t worry about flow coating. Make your goal for this first one just to get it done.
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I'm trying hard not to see that as an aggressive comment because I know it is well intentioned. I am doing my best, and indeed this is only the second car I've painted (though the first was single stage outside for a quickie job) but I do want to do this properly. I also hope I am given some grace here, because sometimes I learn a lot by asking stupid questions, if people are willing to put up with them. I appreciate the support I have been given here. My main presence is the GRM forum (here grm tuna55) for reference.

Anyway given that this is an older truck, it is being panel painted (the backside of the fenders, inner fenders, cab, doors, all show in the finished product) before being assembled. Based on this, what I may do is do the first round of clear over everything, then assemble the truck, then flow coat the assembled truck.

I hear you on the time issue. I simply don't have enough time to do this given my space constraints. The parts were moved from the tent to the garage (I put them in the bed of the truck in that picture, then pushed the whole bed back in the garage). I don't see a path towards basecoat all panels and clear all panels in the same two-day session just based on my personal commitments.
 
Tuna55 said:
I'm trying hard not to see that as an aggressive comment because I know it is well intentioned. I am doing my best, and indeed this is only the second car I've painted (though the first was single stage outside for a quickie job) but I do want to do this properly. I also hope I am given some grace here, because sometimes I learn a lot by asking stupid questions, if people are willing to put up with them. I appreciate the support I have been given here. My main presence is the GRM forum (here grm tuna55) for reference.

Anyway given that this is an older truck, it is being panel painted (the backside of the fenders, inner fenders, cab, doors, all show in the finished product) before being assembled. Based on this, what I may do is do the first round of clear over everything, then assemble the truck, then flow coat the assembled truck.

I hear you on the time issue. I simply don't have enough time to do this given my space constraints. The parts were moved from the tent to the garage (I put them in the bed of the truck in that picture, then pushed the whole bed back in the garage). I don't see a path towards basecoat all panels and clear all panels in the same two-day session just based on my personal commitments.
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Seems logical. Wondering if there is a down side to doing it this way?

I was contemplating doing exactly that on my current project that will be an award winning build and best of show across the United States next year. I also have no doubts I'll be asked to bring my car to Sema next year so it can be put on display.

I'm currently building shelving in my living room for all the new trophy's.
 
Tuna55 said:
I felt that a filtered input intententionally was superior to drawing air in from wherever, which could include around the bottom of the tent where debris is. It felt pretty decent in terms of airflow in the tent, from front top to back bottom. Not windy, but moving, and the fog dissipated pretty well.
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Well sounds like it works well. You’ll want good air flow when you spray clear. It’s twice as foggy as base. Good luck with your project.
 
Tuna55 said:
I'm trying hard not to see that as an aggressive comment because I know it is well intentioned. I am doing my best, and indeed this is only the second car I've painted (though the first was single stage outside for a quickie job) but I do want to do this properly. I also hope I am given some grace here, because sometimes I learn a lot by asking stupid questions, if people are willing to put up with them. I appreciate the support I have been given here. My main presence is the GRM forum (here grm tuna55) for reference.

Anyway given that this is an older truck, it is being panel painted (the backside of the fenders, inner fenders, cab, doors, all show in the finished product) before being assembled. Based on this, what I may do is do the first round of clear over everything, then assemble the truck, then flow coat the assembled truck.

I hear you on the time issue. I simply don't have enough time to do this given my space constraints. The parts were moved from the tent to the garage (I put them in the bed of the truck in that picture, then pushed the whole bed back in the garage). I don't see a path towards basecoat all panels and clear all panels in the same two-day session just based on my personal commitments.
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There was nothing meant by it and it’s great to ask questions. What my comment means is you can tell a person’s skill level based on the questions they’re asking, and when somebody is a novice or a first timer, I don’t find it wise to recommend the most involved methods and procedures. In my own opinion, for that first one you just need to get the product on there and as best you can, don’t try to get fancy. The first one is when all the learning happens and confidence gets built.

As long as you’re not painting a metallic color you can panel paint. But you need to be sure to put the same number of coats on each panel. Me personally, I’d do all the base and clear at the same time for a set of panels and then be done with it.
 
Thanks for all of the input. I chatted with Chad today regarding the Motobase, because I had not realized that there was a time limit between base coat and clear coat. I think we developed a plan where I can save what I've done.

I can clear the inside of the fenders, the inside of the cowl panel, the inside of the doors, the inner fenders, and then reassemble the truck. Once the truck is reassembled, I will block sand the base coat and clear coat the entire thing as an assembly. I think that will suit the problem.
 
Did you activate your base? One of our resident experts @Jim C and others will tell you there is no real time limit to cover your base if it is not activated. He often leaves it for months if it is not activated. His results speak for themselves.

Don
 
dhutton01 said:
Are you planning to block sand your base and then apply clear without shooting more base?
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No I am planning to clear over freshly sprayed base coat. This is a real challenge for me based on my timeline and my logistical issues. I just don't have the time or space to do that well.

What was said above, and what Chad confirmed today on the phone, was that I needed to block sand the base, apply another coat or two of Base, and then clear. He said this specifically because of the potential that some of the clear soaks into the surface and causes a color problem. So we developed a plan where I will clear just the back side of everything as it sits and then assemble the truck. That gives me the logistical ease of putting clear on the entire cab all at once and the entire truck bed all at once once I am done blocking and rebasing. This is all really complicated, and I'm working out of a two-car garage okay one day a week if it doesn't rain, and one temporary Booth set up in my driveway. It's just a challenge.
 
dhutton01 said:
Did you activate your base? One of our resident experts @Jim C and others will tell you there is no real time limit to cover your base if it is not activated. He often leaves it for months if it is not activated. His results speak for themselves.

Don
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I'm not actually sure what that means, I sprayed it reduced per the instructions.
 
Tuna55 said:
I'm not actually sure what that means, I sprayed it reduced per the instructions.
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Then it should not have a closed recoat window. You should be able to wait weeks or months before clearing. But if Chad is telling you to sand your base and respray then I guess that is what you should do.

Some folks add an ounce or so of clear activator to each quart of base. When activated like this base should be cleared within hours.

Don
 
dhutton01 said:
Did you activate your base? One of our resident experts @Jim C and others will tell you there is no real time limit to cover your base if it is not activated. He often leaves it for months if it is not activated. His results speak for themselves.

Don
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It’s not so much the activation but the quality of polyol in the basecoat. I activate all basecoat and still have not cleared it for weeks, as long as it stays clean and out of UV.
 
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