Nitrocellulose lacquer help

Tim

Hi folks - finally had time this weekend to start work on my first build with a cheapo ebay body from boobooguitars & some cans from manchesterguitartech.co.uk. 

Sanded and sealed the body with no problems. Few light coats of primer added and it was all looking good. However looking today, it seems when I was moving the body into the garden office to dry I must have accidentally scraped the finish back with a clamp or something. I don't think it has dented the wood - it looks like it has just scraped back the primer back (so it is raised at the edges). I'm really frtustrated - it was all going so well! 

Does anyone have any advice on how to fix this? Can I concentrate on the small area - or do I need to sand back the whole horn, or even the whole front to get a level surface and then re-prime? 

Corvus

Flat the scar out, blow primer over that area. Flat the repair and the edge where the new paint feathers into the old. Just a spot repair basically.
Can't tell how thick it is, but as a general thing the less build the better (against movement, cracking etc.)

JohnB

I think that @Corvus has the "best " idea there (although I have never used nitro on a guitar body :-) ).  Nitro is simply dissolved in a solvent (probably acetone and toluene based) and hardens as it evaporates, it doesn't "set".  When you spray the next coat on, some of the solvent will soften the coat below so it is very fragile for a while  It probably took barely a touch to make that scrape back to wood, so a dent is very unlikely.  That said, the wood is probably still fully sealed so if you can hide the edges by light sanding without breaking the sealed surface you might well get away with just patching it in with white nitro and feathering the edges before the next coat (quicker but not as good as the "proper" way)

lamf68

Get the body sat on a level surface, get a spirit level on it, then spray (if using aerosols) some of the paint into the lid, or other worthy receptacle, then drip fill the gouge using something appropriate like a fine artists paint brush, drip it in until it builds up enough to level or above the surface of the existing finish then flat it back when dry, I always use this method to fill dings and gouges on bodies provided they aint too deep, it works 100% of the time for me.

SimonRF

Don't worry, this is not major. Rarely does a problem require full stripping.

Both suggestions given so far will work. Probably easier to drop fill to build up the thickness. Key it first just to be sure. Leave it to dry, then sand flush. You may find that the original drop is above the surface, but when it dries it dips down, so simply put a bit more on the day after. Absolutely no need to sand all of the top or even horn back. Once done and flush, key the whole top to 600 grit and then crack on with whatever next.

When spraying finish from an aerosol can into its lid the propellant can re-liquefy rather than evaporate off. The lacquer/primer/paint/whatever will be very very cold, very thin and runny. After spraying in to the lid leave it for half an hour to warm up to room temperature and for the propellant to evaporate off. If you've sprayed enough into the lid you'll notice it start bubbling after a couple of minutes. 

Corvus

The reason I'd say whizz the horn flat is because it's very simple, takes 2 mins, and eliminates the issue of over-sanding a drop-fill which is easy for a beginner to do (well, anyone really). And much quicker overall; sand, squirt, sand, done in a hour or two.

SimonRF

Corvus said:

The reason I'd say whizz the horn flat is because it's very simple, takes 2 mins, and eliminates the issue of over-sanding a drop-fill which is easy for a beginner to do (well, anyone really). And much quicker overall; sand, squirt, sand, done in a hour or two.

Good point - listen to this man!

Tim

Thanks to all for the great advice - really helpful. I'm think I'm going to try and drop-fill it. Will report back!

Corvus

Good luck Tim, post pics!

Tim

So, as I'm not in any rush to complete this project i thought i'd try the drop fill method. My thinking being that if I cocked it up, then I'd just sand back as recommended by @Corvus.

Over 2 evenings I built up the scrape by dripping in some primer. Once dry, it looked like this:

After that I took a blade to scrape over the raised area, as described in a stewmac video: 

After gently scraping off the excess, I tried the finger-tip/thin strip of sandpaper method in that stewmac video. I either applied too much pressure, or was using the wrong grit, and it took away too much paint! So I drop filled, left to dry for 24 hours and scraped back with the razor blade again. This time I just gently block sanded the whole area with 600 grit. Finally I gave the whole body couple more light coats of primer, and I was pleased with the result:

Had to wait for a dry/sunny spell to spray the Pelham Blue, which I managed over the last few days:

Yesterday I misted the last colour coat on, and then misted some clear lacquer as described here: http://www.manchesterguitartech.co.uk/2011/09/01/finishing-an-alder-telecaster-body-in-metallic-lacquer/

Finally I did a couple of wettish coats of clear, but on the last the can did a bit of a splutter. What is the best way to deal with these blobs? Just flatten with the blade and gently sand the area again? I'm a bit worried about sanding through and damaging the paint underneath.

lamf68

 

Finally I did a couple of wettish coats of clear, but on the last the can did a bit of a splutter. What is the best way to deal with these blobs? Just flatten with the blade and gently sand the area again? I'm a bit worried about sanding through and damaging the paint underneath.

Don't worry about the clear sputter marks, as long as the blue hasn't run below and the metal hasn't gathered in clumps just continue with clear coats, by the time it's ready for wetting back you wont see the blobs when they've been flatted

Tim

Great - thanks for the advice/reassurance @Iamf68. Had a look at your Facebook page and that burgandy mist tele is gorgeous. As is the copper flake Cabronita...and the blue metal flake..and...yeah, in fact they're all stunning!