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Author Topic: How do I sand final coat of paint???  (Read 5789 times)

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Offline Jeff Rostoni

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How do I sand final coat of paint???
« on: September 21, 2009, 06:14:36 PM »
I used snow white two part perfection by Interlux on the top side.  My final coat of paint went on okay, but has a bunch of very small bumps here and there (despite my rolling and tipping technique).  Anyway, I tested one area by sanding with 300, 400 then 800.  It is very smooth, but I completely lost the shinyness (if that is a word) of the paint.

Any suggestions? 
eekender - Sea Breeze
Lansing, Michigan

Offline Keith Shergold

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Re: How do I sand final coat of paint???
« Reply #1 on: September 21, 2009, 08:37:17 PM »
Yeah, another thin coat of paint, and be careful this time :)

Maybe try rubbing compound and then some polish to restore the shiny-ness, other than that, try, try again!

Offline Bud_Wilson

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Re: How do I sand final coat of paint???
« Reply #2 on: September 21, 2009, 09:06:55 PM »
Jeff My 2cents worth. I doubt you can compound out where you have sanded. I would lightly sand out my little bumps, then wipe down good with a clean rag and alc paint thinner what ever. with a clean brush or roller I would apply a light coat, Bud
'ALL COME  Cap'N Bud.

Offline keithmclean

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Re: How do I sand final coat of paint???
« Reply #3 on: September 22, 2009, 09:44:25 AM »
You could try to wax it in a spot to see if it helps get some gloss back but you'll probably need to add another coat to get it shiny again. If you do wax and it doesn't work you'll have to use wax remover before painting over that area so be careful. The best way to get a smooth finish is to spray it on. You can get a cheap paint gun and hook it up to a compressor to get very good results. If you've never sprayed paint before it can be challenging so practice first with something not so good to get a feel for it.
The klop, klop of water under the bows of a small boat will cure most troubles in this world. -Arthur Ransome

Offline Jeff Rostoni

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Re: How do I sand final coat of paint???
« Reply #4 on: September 22, 2009, 10:56:56 AM »
I received a response from interlux/yaght paint guys.  They definitely do not recommend any sanding on the final coat as it affects the longevity of the paint.  To quote them....

will most likely effect the gloss and overall longevity of the coating. As Perfection cures, the resin floats to the
top of the paint film and acts as the gloss of the paint film. When you wetsand or buff that gloss/resin, you will remove imperfections, but will also remove some sheen.

I am not sure what the little bumps are (about 4-7 per square foot), but I think I will lightly sand and put on a VERY thin final coat and just call it good!
eekender - Sea Breeze
Lansing, Michigan

Offline Paul Riccelli PE,NA

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Re: How do I sand final coat of paint???
« Reply #5 on: September 22, 2009, 12:33:58 PM »
I don't know why the manufacture told you that bit of information, you can buff LPU and it's done all the time. The key is to work up to the grit necessary, without removing too much material. Typically you need to go to about 1,200 or 1,500 grit before it worth considering a buffer. You can cut down the amount of sanding necessary if you use a cutter compound on your buffer, then switch to polish.

If you intend to apply paint over these areas, don't use compounds, polishes or waxes at all, they'll contaminate the surface and the paint will fish eye like crazy.

If you intend to paint over the area, then no more then 300 grit or you'll not have enough "tooth" to hold the paint .

I've "fixed" many a LPU paint job with a buffer and DuPont products. It's kind of surprising I've been doing it wrong all these years. Maybe it's because they want you to buy more paint and not cutting or polishing products.

Offline Keith Shergold

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Re: How do I sand final coat of paint???
« Reply #6 on: September 23, 2009, 09:59:08 AM »
Yes, it's true. I bought some paint a while ago from a new manufacturer, It was an LPU but I can't remember why it was different than other paint (I haven't used it yet) but for some reason it only came in a semi-gloss, the paint guy told me I should polish it with a buffer to make it glossy if I wanted to. It was pretty darn expensive paint and the advice came straight from the manufacturer.

Those little bumps might be stray dust particles that landed in the paint while it was still wet, or, if you tipped it with a foam brush, I've noticed the foam doesn't particularly like the paint, it gets mushy and after a while starts to shed little particles.

Offline Jeff Rostoni

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Re: How do I sand final coat of paint???
« Reply #7 on: September 24, 2009, 11:49:21 AM »
Yeah Keith...I wish I could figure out what the particles are.  They are litterally the size of a 12 point font sized period (like at the end of this sentence), but it is noticeable visually and to the touch.  I bought chemical resistant foam rollers from Jamestown distributors and then tipped the paint with a decent New China bristle brush (forgot the actual name).  The "particles" seem to have paint on them so not sure if it is something during painting or after.   Screw it.  I plan on putting a bit of textured paint on the boat then I will just lightly sand and gently repaint the non-textured areas one more time with very thin layer of paint. 

BTW - I think you can buff, wax, etc. this paint, but I think the point interlux was making is to make sure not to reduce or compromise the paint surface as it has protective properties to it. 
eekender - Sea Breeze
Lansing, Michigan

Offline Andrew_Butchart

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Re: How do I sand final coat of paint???
« Reply #8 on: September 25, 2009, 02:02:13 PM »
Some of the best advice I ever got about boat building was that the first thing to do after finishing was to turn the boat over and put a big scratch in the paint.  That way you wouldn't be afraid to use it  ::)

Last weekend I put away my Mouse-Boat after a river trip.  I used my wood rasp to clean up some wood fibres that were loose on the keel strip, gave it a couple of shots of rust paint with a spray can  over the whole bottom and tossed it up into the rafters of the garage where probably it will get real mouse and chipmunk footprints in the paint.

It's a great little boat.