what grit to wet sand primer before paint

• #1

I have read a number of threads claiming that a final primer coat should non exist sanded with grit finer than 400 or 600, or your coat of paint won't attach well. Given that lacquer adheres by melting into the proceeding coat, wouldn't it be OK to lightly sand the final glaze of primer on the BT or nosecone with 800, one thousand, or even 1500 grit prior to applying a coat of lacquer spray pigment?

• #2

I have read a number of threads challenge that a terminal primer coat should not be sanded with grit finer than 400 or 600, or your coat of paint won't adhere well.

I don't believe that to be a fact. I've wet sanded primer with 1000 grit, the paint sticks only fine and turns out looking similar glass.

I know 'hot-rod' body men/painters that actually -buff- the primer. The smoother the base glaze, the smoother the pinnacle coat...

I accept wet sanded up to 2000 dust in between color coats. Zero similar making a spray bomb paint job looking like information technology was done with a HVLP

• #3

I don't believe that to be a fact. I've wet sanded primer with m dust, the paint sticks just fine and turns out looking like glass.

I know 'hot-rod' trunk men/painters that actually -vitrify- the primer. The smoother the base coat, the smoother the height coat...

I take wet sanded upwardly to 2000 dust in betwixt color coats. Zero like making a spray bomb paint job looking like information technology was done with a HVLP

I accept to disagree strongly with jeffs response;
As a professional painter nosotros are taught by ALL the major pigment manfacuters that final primer coats should be fine DRY sanded with no more than the 360-400 grit sand paper. Because primer is by its chemistry porous wet sanding can and will cause water to migrate all the fashion to the substrate (on cars bare Metallic - on most model rocket cardboard) which can cause Rust or delamination of the body tube). Wet sanding is a technique intended But for utilise on the Finial Top coat and/or Clear Coats.

The reason for not sanding primer beyond 400girt is the surface needs a picayune tooth ii allow the pigment to adhear better to the micro peaks & valleys left by the grit.
Remember the Merely matter that keeps paint on whatever surface is Surface Tension (the lack of air between substrate and paint film). Yep, the platelets of pigment in pigment overlap and interlock forming a dry film but they practise Non melt into the underlayer. It is the thinners and vehicle that crusade damage to the underlaying layers.

• #4

I empathise the wet sanding primer issue and I volition merely dry sand primer. My question just pertains to how fine a grit can be used for dry sanding primer prior to applying lacquer. I have read tons of painting threads here and have accept non been able to discover a single one that discusses someone having bug with lacquer adhering to primer because they sanded the primer with too fine a grit. I'm get-go to think this idea that you lot should not sand primer with annihilation effectively than 400 or 600 grit prior to spraying information technology with lacquer (so there is "tooth" to hold the lacquer) may be a myth that has been often repeated). Searching google I find most auto painting instructions telephone call for sanding primer with yard grit prior to spraying. (They of course moisture sand the primer, which I won't). Has anyone e'er heard of issues with dry sanding primer with thousand or 1500 grit prior to applying a lacquer glaze? If you know of a thread that discusses issues with this, I'm really interested in finding out.

• #5

I've washed m grit on car spray gun primer prior to shooting base of operations coat and so 1500, 2000 on base coat before clear. Never needed to e'er cutting my clear coat or smoothen...ever. I take Into consideration the materials used, the surface area, the prep, the colors, temp, drying fourth dimension and surface. Merely way to figure out what works for you and to find what you are adept at is trial and error and experience.

I say do what you lot want and run across what works and how it come out. That'south what I cut my teeth doing and yous will be surprised at how good it comes out. Take into consideration the advice and general practices that are out there and make them your own.

• #6

Too to moisture sand you don't demand to fully wet out the area yous are sanding. Lately I've been using a spray canteen with water and about 2oz of simple green to spray the sand newspaper, sand my small areas at a time, wipe the sand paper off on a towel, the. Wipe the surface area Sanded with a damp towel and move on. I too don't use much pressure and let the paper exercise its matter especially if I'm not using a cake.

For the final wet sand spray the paper again and go over it one time. Don't need a bucket and wetting out the whole area and all that... yous can only I salve that for painting fibglass/carbon. Let it dry out for a twenty-four hour period before you spray and wipe with wax/grease cleaner, wipe on, wipe off.

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Source: https://www.rocketryforum.com/threads/sanding-primer-coats.131901/

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