Please Help With Finishing.....

[chuck11976]

I have a question that is for an experienced professional in the area of guitar finishing. How do I go about getting that "rock hard" clear coat finish on my project strat. I have tried several things before but none of them come out like the guitars I pull off the shelves in a store. Those finishes are ROCK HARD. Mine are nice and mirror glossy but seem to stay soft, like I can put a fingernail impression into the finish even months later. Why? Please walk me through PRECISELY what to do. Thank you so much.

[Vince D]

What type of finish are you using?

[chuck11976]

What type of finish are you using?

At this point I'm looking to you guys to tell me what to use. My main concern is the "HARDNESS" of the finish. What is the big industry secret to that HARD finish?

[Maiden69]

Auto paint! not from a spray can! You can use nitro but 2 part poly will be harder anytime!

[Drak]

That's easy. You need:

1. Professional spray equipment

2. A professional finish to use, a crosslinking finish like Polyurethane, Polyester or Catalyzed Lacquer

3. Professional Rubout and Buffing equipment

4. Much Experience using one or more of these products

...and even on a good day, you can put a fingernail in lacquer if you try, lacquer is not a rock hard finish.

It has it's good points and bad, and I like it, but 'rock hard' isn't one of it's strong points.

Lacquer is a film finish, and ANY crosslinking finish will kill any film finish any day of the week hands down for 'rock hardness'.

[croaticum]

+1 to Drak.

I use all nitro finishing thingies.

nitro paint, nitro gloss nitro anything.

When you paint a car, after aplying clear coat, paint gets "baked". Basicly they heat the painting booth to certan temperature and "bake" paint. I do that on my guitars, but that is just thing to make it dry faster.

[chuck11976]

That's easy. You need:

1. Professional spray equipment

2. A professional finish to use, a crosslinking finish like Polyurethane, Polyester or Catalyzed Lacquer

3. Professional Rubout and Buffing equipment

4. Much Experience using one or more of these products

...and even on a good day, you can put a fingernail in lacquer if you try, lacquer is not a rock hard finish.

It has it's good points and bad, and I like it, but 'rock hard' isn't one of it's strong points.

Lacquer is a film finish, and ANY crosslinking finish will kill any film finish any day of the week hands down for 'rock hardness'.

Drak-What does "crosslinking" mean? And could you specifically give brand name, part number, whatever specific info on a particular product. I am familiar with polyurethane but what is polyester? Brand name and part number for polyester?

[Southpa]

Crosslinking is also called polymerization. During the curing process simple molecules bond with each other to form more complex molecules. This makes the hard, rigid surface you are after. One drawback to using this group of finishes is the potential for hairline cracking along glue joints when the underlying wood expands and contracts. So your wood better be well cured and your joints nice 'n tight.

Polyester is also in that family of finishes, basically anything that begins with "poly" crosslinks but there are different types of curing reactions as well as different chemicals involved. As far as specific polyester products available your best bet is to google around.

I found a video (.mov) that explains these types of reactions very well. They basically deal with coatings used on steel substrates ie. shipbuilding, rather than wood, but the concepts are the same. If you have high speed connexion you are welcome to download and view them.

I've included another that explains solvent evap. coatings (eg. lacquer)

[Drak]

That is a most excellent answer Southpa, the only thing I wanted to add was that people think these finishes are 'harder' than shellac or lacquer, as if there was a hardness scale and lac was a 3 and poly was an 8 or something, but really, they are simply a completely different animal altogether.

Instead of the word 'harder', the word 'tougher' should be used, this is a more accurate definition of what a poly finish is compared to lacquer.

Tougher refers to the crosslinking action as the finish dries.

The 'tougher' a finish is, the harder it is to buff out, and the less clarity you'll get out of it.

That's why lacquer is still used so much, because although it's not the hardest finish, it offers the most CLARITY, the most 'see-thru' gloss, you can get, although manufacturers of other finishes are getting pretty close now, but you need industrial buffing machines to get the gloss from them, lacquer can still be rubbed out by any amateur with the right equipment to a very high professional gloss.