Well, with all due respect to other folks opinion, I always hear this "don't wet sand primer" from people who don't wet sand primer... but I do it and I can tell you that in my experience having done it for several years, that it isn't a problem and the results are really amazing!

Take that for what you will.

Later! OL JR

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I worked in a body shop one summer in college (1983). We wet sanded cars before painting them. But we didn't wet sand the soda machines, which were painted in the same shop. The way I was taught, wet sanding was mainly for managing the dust moreso than for any improvement it imparted to the surface. Also, it extends the life of the paper.

My experience has been that I can get an incredible finish without wet sanding. So I've never tried it.

But I'd bet a dollar to a doughnut that there are lots of rocketeers out there who have tried it, and made a heckuva mess of their wood and paper rockets (But have kept those embarrassing little secrets to themselves ) It's not something to do without taking great care. A bit of moisture in the wrong spot and you'll have raised wood grain and/or blistered paper.

Some folks only recommend it when sanding painted surfaces, versus primered surfaces (eg, sanding lacquer between coats).

Anyway, I'm sure, with care, it can be done without damaging the rocket, but I still question whether it improves the underlying surface any. I can get an amazingly smooth surface using dry 320 or 400 grit.

[Edit:] BTW, I did bugger up a rocket one time getting it wet using a damp rag to wipe off the dust. The moisture hit a thin spot - real thin - in the primer and the underlying paper blistered like jiffy pop.

Doug

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YORF member #11

I just don't see the point of wet-sanding primer. But then, I don't see the point of using tons of primer as a grain and spiral filler, either. If the base surface is smooth and you apply the primer well without runs, etc, then the primer layer will be smooth. If the primer layer is smooth, then the finished paint layer will be smooth. It's as simple as that. Wet-sanding rarely if ever enters the picture once I get to the painting stage. With sufficient base surface preparation it isn't needed.

But if wet-sanding the primer makes you happy, then go ahead and do it. I'm not going to stop you.

I do use wet-sanding, as I said earlier, to smooth down the sealer layer on wood parts (mostly nose cones), but that is during the base prep phase, prior to applying primer and paint. It's a great technique and does a wonderful job there. In the event that I get paint wrinkling or orange skin, I also wet-sand the defective paint layer thoroughly as part of the repair process.

All of this is just what I do. There is more than one way to get to the same goal, though. Try different things out and feel free to develop your own process. I learned how to paint my model rockets that way.

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SAM # 0011

Well I think you've summed it up nicely. There's no right or wrong when it comes to finishing; right is at best defined as what works for you to deliver the results one finds acceptable. It's been my experience that the most important thing is to find a method one is comfortable with, and then like most things, practice, practice, practice. The greatest improvement comes with the diminishing learning curve.

I must admit that on models for which I'm striving for the best finish I can muster that I will indeed wet sand the primer. The reason for that is that no matter how well I fill the seams and the crack and crevices around fin fillets, there will nevertheless be something that I've missed, or perhaps the solvent in the primer will shrink the seam filler somewhat, etc, etc. It means a little more filling work and another coat of primer to get that perfectly smooth base surface. Well one can't very well dry sand spot putty (I use Squadron White putty for this stage) without causing a problem with the surrounding softer primer. Wet sanding solves this problem, and I've found little else that feathers as smoothly as Squadron White putty when it's wet sanded.

Ah yes, but what about Doug's excellent point about rub through/wet pops, especially when he's right? Well that problem gets solved by laying down two successive coats of primer (allowing for a full cure in between) before any subsequent patching and wet sanding takes place. In my case, I've never have had a mishap when finishing this way.

A lot of work, and as I say, in my case performed only for those models where the best finish is required. Wet sanded primer subsurface, below.

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John
YORF #003
SAM #004

NON wet-sanded rocket here...

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SAM # 0011

I'll wet sand, even primer, depending upon what type of material I'm sanding so as to reduce clogging up my sandpaper. Build-up primer, for instance, is made to be sandable so doesn't need wet sanding. But, regular primer builds up really easily, wasting sandpaper right away, so wet sanding works much better. That's also why I wet sand paint.

I agree I like Duplicolor too...some of the better paint I used. Stay away from Rusto gloss white

Sweet!!!

So what is the difference between "build-up" primer and "regular" primer? I have Dupli-Color Filler Primer that I am going to guess is build-up primer.

- Rich

Primer with more solids in it. It lays down a thicker coat so that it can be sanded back down level, sorta like "spray on filler"... Regular primer has less solids, so it goes on more like a thick layer of paint (thinner layer than the "high solids" primers). The gray and red primers are usually "regular primers" but they usually are also available in "high solids" (build-up) type primers as well, and labeled as such. Some primers, especially white primers, usually end up thinner than 'regular' gray or red primers... that's why I don't use white primer. I LOVED the Walmart Gray and ESPECIALLY the red primer from Walmart, because two coats of that and you had a GOOD STRONG base of primer to sand down and get a perfect surface ready to paint... sorta in between "high solids" primer and regular primer IMHO. Now that WM doesn't sell either one any more (in our area anyway) I picked up a can of Rusto Red primer and I'm trying that.

Later! OL JR

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