Sandpaper Marks Visible in Endproduct?

[Orchidius]

Hi there,

I'm putting a whole new paint system on my cabinroof, and parts of it had to be sanded by hand with 60 grit sandpaper. This of course led to some nasty sandpaper scratches that are pretty deep. My concern is they will show in the end product, but I'm not at all sure and sanding the whole thing again with 220grit as recommended by the paintcompany is a ****ton of work... I've also tested a section with a spraypaint can I had at hand. After the first layer the marks were still visible, but after a second pass they were gone.

So here's what I'll be putting on as the new paint system: two layers of primer, two or three layers of finish paint and a last (extra durable) layer with anti-skid in it. Before anybody jumps on that last bit, the non-skid will be in patches, so it won't cover all imperfections .

Watcha reckon'?


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[robert sailor]

I recon that you will see the scratches. The paint prep is 90% of what makes a decent paint job, now is not the time to avoid the work.

[Mark1977]

Originally Posted by robert sailor

I recon that you will see the scratches. The paint prep is 90% of what makes a decent paint job, now is not the time to avoid the work.

+ 1..

[Orchidius]

Is that speaking out of experience or the general knowledge that it's best to put in a little extra prep then to redo the whole thing?

The latter is obvious, and I'll take that route if I have to. But experience also teaches me that I tend to be overly perfectionistic, and in this case that would cost me the remainder of my summer holiday with half the refit still to do...


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[Bluemansailor]

60 grit is pretty course grit- only way to get rid of the scratches now is A LOT OF HARD WORK- 80 grit, 120 grit, 150 grit then finally 220 grit.

Sorry but like everyone said prep work is 90% of the work, It shows in the end.

[Cheechako]

High build primer.

[barnakiel]

I would use paintmaker's recommendation as a baseline.

b.

[hellosailor]

Phrase it another way:

Follow the paint maker's advice, relying on the fact that they don't sell sandpaper and they don't want to make using their product any harder than it has to be. A ton of work.

Or, don't follow their advice. And then it will be four or five times as much work to get a lot of expensive primer and paint ground all the way back down again before you have to redo the whole paint job again.

Hmmmm.....What to do, what to do....

Buy a couple of good small power sanding tools perhaps?

[dlymn]

Experience. Never use 60. Work your way through the grits. You will find that you'll spend much less time on each grit than your initial scouring. Power tools help. Hand sand along the grain of wood and along the most likely sight line of gel . Paint is only microns thick and is only as good as was what you lay it it onto.
I recall the lads of Nice. Working on their antique fishing boats, sanding, sanding. The shared bottle of Jack seemed to make the time fly for them

[gonesail]

start with 150 and go to 220 .. sanding is fun .. sand until you cannot sand anymore .. then it will be ready to paint

[thinwater]

Buy an electric sander. Use a Multimaster in the tight spots. There should be little hand work.

And work your way though the grits. It won't take that long on each and 150 is probably enough with that paint schedule.

And don't use 60 in the future. I ONLY use that for very rough work on FRP with a disk sander. 120 should be the workhorse even for rough stuff.

[a64pilot]

Originally Posted by Cheechako

High build primer.

which is nothing more than talcum powder in regular primer, but if you want to fill scratches, that is exactly what it is made for

[IdoraKeeper]

You can think about wet sanding, might go a bit quicker and reduce the dust.

[Neo]

I just refinished the bow portion of my deck (replaced rotted core). I sanded down to fiberglass with 80 grit and some limited 60 grit. I would suggested starting with an epoxy barrier coat before priming and painting. I used two coats over 80 grit sanding, and no visible scratches remained. I followed with 2 coats of primekote and 3 coats of interlux perfection with 120 - 220 grit sanding in between coats. There is no way 80 grit scratches will show through that, in my very humble and unprofessional opinion. Bubbles are the real problem.

It is my understanding that the fine grit is more about creating better bonding of the paint to the previous coat.

Epoxy barrier coat. Probably get the same result with high build primer, as Cheechako said. If you can still see scratches after the barrier coat, then sand your little heart out.

[darylat8750]

I just made the error of thinking high build primer would fill 80 grit scratches. Sand to at least 120 grit before wasting that expensive paint.