White specs in nitro finish

greggreg66

I've been polishing my explorer today and now it's getting closer to completion, it's covered in a rash of white dots, and it's really depressing! 

As far as I can see there's still the tiniest of tiniest of tiny open craters in the finish (I hate nitro), so I can understand that these could have become filled with the polishing compound.... but they don't go away with naptha or water. They got worse (as in increased in numbers) the more I polished. My process:

1. Dry orbital sand 400 / 500
2. Wet sand 1000 / 1200 / 1500 / 2000 / 2500
3. 3 buffing compounds, with the last one done by direct drive sander on lowest speed with added water (borrowed a mates sponge mop and while it polished well, it left some horrible swirlies!)
4. I know there's some scratch marks in there, I don't consider this finished yet : ) 

Aside from re-finishing it, does anyone have experience of this and overcoming it? If I can't turn this around 100% I'll be going to PU for future finishes. 

Any help would be greatly appreciated. 

ps it's already starting to check in places. Not sure how I feel about this yet ha! 

SteveRobinson

It looks like buffing compound in the pores. Did you grain fill and seal before the lacquer coats?

greggreg66

SteveRobinson said:

It looks like buffing compound in the pores. Did you grain fill and seal before the lacquer coats?

Yes, I think it's the buffing compound in the pores too.... but I can't discount that there's trapped bubbles from spraying. 

I didn't grain fill & seal*, on my last guitar I used a mix&fill grain fill and the nitro didn't like that so for this one I was happy to building the coats up with the knowledge it would take many coats. 

* I did do a couple of coats of well thinned nitro ahead of a colour coat to seal it, but I didn't used "sealer" for this. Certainly with PU this works fine doing this method. I thinned all the lacquer to around 30%. I was spraying with my cup gun. 

greggreg66

@SteveRobinson ;I just find nitro so odd the way it does open craters, it's just behaves so completely different to other lacquers I've sprayed (AC, preCat, PU & acrylic PU). 

greggreg66

I think it must just be that the grain is still open and this has trapped the buffing compound. It's done it on the face of the headstock, but that had a beech veneer so the grain is closed and therefore no white dots. 

I've heard black wax can help so I might try that..... can't face respraying it at the moment!

Winny_Pooh

This should have been noticed and fixed in the spray or flatting stage.

greggreg66

Winny_Pooh said:

This should have been noticed and fixed in the spray or flatting stage.

Yeah. Having tinkered with it further it's pretty clear now that the grain is far from filled - nitro isn't particularly high building. Black wax has helped a lot and it's looking much better in the flesh now. Lesson learned here I think!!

Nitro isn't forgiving enough IMO to be sanding too much between coats as it clogs paper so quickly, but I guess that's missing the point to an extent as if the wood is open grain then it needs to be filled as otherwise it'll fill with buffing compound later! Not a prob if it's a white guitar haha!

SteveRobinson

You don't need to sand between coats if you get your preparation right which means grain filling open pored woods and using a sealer coat.

greggreg66

SteveRobinson said:

You don't need to sand between coats if you get your preparation right which means grain filling open pored woods and using a sealer coat.

Thats why I said I'm missing the point about it needing to be sanded between coats if the prep is done right.... which I didn't do this time 

nickaslin

Were you wearing an Aerosmith t-shirt? If no, why not?

greggreg66

nickaslin said:

Were you wearing an Aerosmith t-shirt? If no, why not?

Oh man! So THATS why it went wrong!