Finishing with Poly - So Close Yet Not Quite

[PopsOldman]

So long story short; bought a DIY kit, watched tons of videos, had my fair share of bumps (some quite literal in one attempt at finishing with poly) and am at a pretty good, yet so annoying place right now in the project..

The high grit wet sanding made the feel of the poly so nice, but every final coat had brush strokes.  Wet sanded with high grit again then saw some advice to add 10% mineral spirits to the mix.

Now the finish looks AMAZING... but only when it's still wet.  Unfortunately it always dries to this white, salty looking, faded old car in the sun weak finish.  If I put water on it, it looks great, then it evaporates and I'm back to the old dried out car paint look.  

So what exists in the world that I can use that will not cause brush strokes, will dry yet keep that wet look, and can sit safely on several layers of pure minwax poly (oil modified) and not cause even worse problems?  Do I just need to say this part is over that I have the good coat and wax/finish/polish now?

Let me know please.

Thanks. 

[curtisa]

Sounds like you've taken things as far as you can with the sanding. Have you tried buffing the finish with some kind of compound or paste cream to see what happens if you go for that last step? There are all sorts of buffing compounds that can be bought at a local automotive outlet that will polish a clear finish to give it that liquid glass effect (Meguiars and Autoglym products are a couple of popular ones).

[Bizman62]

Brush strokes are a similar issue to the orange peel of spray guns. The recipe for a glossy finish is also similar.

My first build, a Tele, is shiny but bumpy and on close look the orange peel is partially visible. On the second build I managed to make a perfectly glossy clearcoat finish on a Strat body.

Here's how I did that: After the final coat I took a pretty hard block and wet sandpaper and leveled the surface sanding one direction only, back and forth though. The flat block is essential as it makes the paper run on the high spots only. When all the orange peel "pores" similar to your brush marks had vanished I wiped the body clean and changed to a finer grit and changed the direction of sanding by 45 degrees. After all the scratch marks of the first sanding had vanished I went finer, again at a 45 degrees angle compared to the previous sanding direction. Rinse and repeat up to 1500 grit after which I changed to a 3000 grit 3M Trizact foam based pad, followed by a similar 6000 grit one. Already after 3000 you couldn't actually see any sanding marks but the clearcoat had a milky shade. Less so after 6000 but there was a significant difference between a wet and dry surface. I then used a swirl removing rubbing compound for final polishing the clearcoat. All that was done by hand, no machines involved. Muscles I didn't know to exist cramped...

Car paint shops can be good for finding better fine sanding products, after 1000 grit I used dedicated automotive clearcoat sanding pads instead of paper based ones.

[ADFinlayson]

wipe on polys are not thin enough for guitar finishing IMO, not if you want that glassy look. Thin your last few coats to at least 70/30 - the material will self-level better than 90 or 100% poly and it will dry faster too.