Grain Fill, but I already shot primer

[swarfrat]

So after a 2nd coat of primer, it because obvious that primer can't bridge Ash pores well. But where do I go from here? Do I need to sand back to bare wood? Even doing so wouldn't get the primer out of the pores - so that makes me think I should be able to fill / bondo / something on top of existing primer without going all the way back to bare wood. 

Can I just sand it back level and grain fill or am I stuck with 47 coats of primer at this point?

 

[AirCap]

47? Really? The grain should be filled and then some by now.

Seriously, sanding it all off is not the answer. Just keep shooting until the grain is filled, and sand level.

 

[Toulouse_Tuhles]

Ditto.  You'd have to sand to the bottom of the canyons to get the filler to work well, so let the primer really, really dry (cure) and sand it back well.  Repeat until smooth.
In the future.... Just tossing this out for an opaque finish on swamp ash....  I've used super glue to fill the grain.  Goes on well, dries fast, sands back perfectly.  Just use it with lots of fresh air.  I did up a swamp ash blue sparkle (metal flake royal blue) tele that way and it was one of the better, and easier finishes to get perfectly level.

 

[swarfrat]

Ok, should I spray multiple coats between sanding back? Last time I think I was sanding back too soon, ended up just doing an endless wax on wax off thing, undoing what I'd already done.

 

[Cagey]

That's kinda the price of filling with primer. Better off with grain filler, but you're past that option now. Just be sure to let it dry thoroughly to prevent future shrinkage.

 

[stratamania]

If you have a solid primer on there and you are going for a solid colour here is an idea. This is not something you would normally see in guitar finishing but in the decorating world is used.

You need something like some interior plaster filler such as made by Polycell (not sure if this brand is available in the US). You use that to fill the gaps in the primer and sand smooth. Repeat the primer and filler again if needed. Then move onto your top coats after you have a level surface.

 

[Toulouse_Tuhles]

Another thought is to just "prime" the places with the deep canyons of grain.  Swamp ash gets those really rough spots in the dark areas, and the lighter parts are usually pretty smooth.
But, temptation being always present, it cannot be over stated:  Let the primer, filler, whatever.... really, really dry before sanding.  Remember, the filler material is thicker material, so it takes longer to fully cure.  Worst case is what happens with lacquer.  It dries, you sand, it continues to shrink, and later on.... you see its not level.  So you apply more hoping to sand again.  What it does is swell the lower material already there.  You sand... it shrinks.... you chase your own tail like a hapless mutt 'neith an August sun. 

Another trick is to apply sort of thick, and as it dries "scrape" the filler into the canyons for better build up.
And finally... always, always... use a hard sanding block, never your hand/fingertips on the sandpaper. 

 

[mayfly]

In the future.... Just tossing this out for an opaque finish on swamp ash....  I've used super glue to fill the grain.  Goes on well, dries fast, sands back perfectly.  Just use it with lots of fresh air. 

That sounds like a pretty good idea!  I'm gonna try that...

 

[Toulouse_Tuhles]

This one has the super glue grain fill, and was really Grand Canyon-esque swamp ash, very light weight, really coarse grain.

I thught there were more pictures of that guitar somplace in the gallery, but I can't find 'em.  It was about ten years ago.
And the pic is before final level and buff... sorry, its the only one I have of that gitfiddle.

 

[stratamania]

Your pictures are not showing up well. Possibly due to being hosted on Photobucket.

 

[swarfrat]

What pics? Mine or Toulouse_Tuhles? I didn't post any pics in this thread, that might be why they're not showing up.

After I started contemplating cure times I'm inclined to just take it back down to bare wood and shoot something else. If I go to bare wood, I'll still have primer coated pores. I have a HF HVLP gun, but didn't see anything suitable at the BBS. I don't give a rip about Nitro, but I do like the fact that shellac dries so quickly. 

If I go back to bare wood (+ pores, this is an oil base primer) - will shellac allow me to shoot a spray laquer or epoxy or something else over it?

 

[stratamania]

Toulouse_Tuhles photos...

 

[Toulouse_Tuhles]

.....If I go back to bare wood (+ pores, this is an oil base primer) - will shellac allow me to shoot a spray laquer or epoxy or something else over it?....

Yes.  Shellac is very forgiving that way, being alcohol solvent based.  However.... that first coat or two of nitro over the shellac should be thin, allow full cure.  Sort of like lacquer over a waterslide decal.  Gotta be gentle with it for safety sake. I've got a picture of a guitar I did with two dark fillers, then shellac, then nitro.  Its another one of those deep grain ash bodies.  But... pictures not showing?  Heck, they show on my phone and tablet as well as this desktop. 

 

[stratamania]

The photo may not be showing due to it being on Photobucket for some reason. I do have a plugin in this browser which was to workaround Photobucket blocking images showing up hosted on Photobucket. But in this case, it may be having the reverse effect if you have a paid account with them.

I could see them in another browser without the plugin.

A lot of us ditched Photobucket a couple of years ago when they changed their way of doing business.

 

[swarfrat]

Decided that the difference between sanding back to bare wood and sanding back to level might effectively be the same thing. Still need to sand the sides (PITB) but on the front and back, I've got a decent primer fill on the pores now.  This stuff loads up the sandpaper really fast though.

 

[Cagey]

Get a small dish of naptha to dip/wash your paper in as you go, and it won't load up nearly as fast. Also, wipe the thing down from time to time to get the bulk of the sanded material off the body while you work.