Confused, first project.

[Warheart87]

In short:

I had planned on handing over my recently delivered unfinished alder body to my local painter and let him do the job. But he turned me down since he only work with metal and plastic. (There aren't alot of painters here in northern Sweden.) He told me to get some primer on the body and then come back and he might be able to help me. Now everywhere I read about sanding sealers, grain fillers etc, and it's really confusing me. The alder body feels very smooth, and I wonder if I can just put primer directly on it?

What is the abolut first step I should do here? Any help is highly appreciated.

 

[Cagey]

If this painter works primarily with metal/plastic and isn't familiar with wood surface prep, I'm not sure he'd be the one I'd look to for body finish work. He's not going to save you much trouble, and you may not get the best finish. There are exceptions, though, and I'll get to that in a moment.

But, first, you should know that finish quality is about 70%-80% prep work. Shooting the color coat is easy, then some clear coats to give it some quality and durability with a little conditioning work between coats, then buffing it out come next. That's all assuming he shoots lacquer and has a proper buffing setup, which isn't likely for the kind of work he does.

The exception would be if he's set up to shoot catalyzed finishes. If that's the case, then it all gets dramatically easier. You still have the prep work, but the color coat is the last step and you're done, unless a clear coat is added for effect. Shoot it and forget it; it'll be beautiful and won't require multiple coats or buffing out. With proper prep, you'll have something that looks like wet glass 15 minutes after it's begun to cure, and will take a surprising amount of abuse.

As far as prep, Alder is pretty fine-grained for such a lightweight wood, so it generally doesn't need grain filling. Prep mainly involves getting a pile of 320 grit sandpaper and a quart of filler/sealer. Shoot it, sand it back a bit, shoot it again, sand it back a bit, and do that for about 4 or 5 coats. Of course, if you can do that, you can probably just continue on with the color/clear coats as well, so you don't need any help. Just toward the end of the clear coats, you graduate toward finer grits of paper, finishing off with a ride on the buffer.

 

[Warheart87]

Yeah, he said he wasn't set up for wood at all but would think about it if I could get it primed. I was lucky today however and found a custom guitarbuilder here in my town which happily took on my project.

But for future projects let me get this straight:

Sealer/filler, sand it down and repeat 4-5 times.
Then I prime it or go straight for the color coat?
And finally some clearcoats.

Thanks again Cagey!

 

[pabloman]

Hope it works out. Who is the builder?

 

[Cagey]

With wood finishes, the sealer/filler is the primer, in that it conditions the surface for final coat. Primer usually refers to an interim finish designed to mate dissimilar materials that don't want to mate, such as paint and metal. The chemistry is such that primer will stick to metal pretty well and provide a ready surface that paint will stick to.

In wood finishing, you don't usually have a problem with the paint sticking to the raw surface. But, wood is porous and has varying degrees of roughness to its surface, so you want to fill in the pores/grain and seal it from the final coat so the wood doesn't suck it up. Hence, the sealer/filler steps.

Of course, you can shoot primer coats on wood as well, it's just unnecessary.

 

[Warheart87]

Very informative, that clears up alot. Thanks!

Here is the builder Pabloman: www.guitarworks.nu and Jakobsson Guitarworks on facebook.
He does some nice stuff!