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I am thinking about taking the plunge into polyester finish. I am needing some information from those who have experience working with it.

Any recommendations on brands? I am not looking into UV cured, just the catalyzed stuff.
Can it work with west systems epoxy as my pore fill?
Can anyone give an example of the schedule for applying it (i.e. fill, seal, topcoat times, etc)?
Can it be touched up invisibly?
Safety equipment requirements?

Thanks.

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Hi Chris

Years ago I used McFadden's on my first guitar, and it was easier than I expected. I don't know if it's still available or not under a different brand. These are my notes from Rick Turner.

• Shoot in a full body Tyvek suit and a respirator rated for the finish.

• Epoxy pore fill, then sand to bare wood.

• Two thin coats of Waterlox. This is the tie coat that enhances adhesion of the remaining finish coats. Wait 24 hours. Foam brush the Waterlox on, wipe off with blue paper shop towels.

• Then shoot two coats of McFadden Rosewood Sealer on everything 2 hours apart. Wait overnight. Scuff that with maroon ScotchBrite.

• Three coats of poly 40 minutes apart. Level the next day.

• Rub out with 400 (only if needed to knock down sags), 600, 800, 1000, 1200, Menzerna 38, Menzerna 16.

• Fit bridge to top by lightly adhering 150 grit self-stick sand paper to the top and sanding.

• Glue bridge directly to poly with the orange label (medium viscosity) “Super T” super glue. Clean off any buffing compound with super glue solvent and clean the underside of the bridge with acetone. Clamp for about 30 minutes, clean up squeeze out with super glue solvent, and leave it another couple of hours.

McFadden ratios:

•Sealer mixed with 20% hardener

•5 part sealer to 1 part hardener

• Polyester thinned 25% with MEK. Cure with 2 oz. of cobalt drier per gallon, then add 2% by volume of MEK Peroxide with a medicine dropper.

• 2 to 3 ounces of poly thinned 25% with MEK takes care of a coat on a typical guitar.

• A very handy rule of thumb formula is 1 cc of cobalt and 1 cc MEKP for every ounce of McFadden polyester. DO NOT MIX THE COBALT AND MEKP TOGETHER! Add the cobalt and dye, stir, and let sit for at least 30 minutes. Then add MEKP and MEK thinner, and shoot within 20 minutes or so. Run acetone or MEK through the gun immediately when you’re done unless you really like cleaning out solidifying goop. Catalyst ratios change with heat. Reduce the amount of catalyst if it’s over 90 degrees F. I used the disposable 3M Paint Preparation System cups, and there’s a liner with markings in ounces and also ratios. It’s very handy for mixing catalyzed finishes.

I use the stuff from Simtec,

http://www.simteccoatings.com/

I only use their 28X50 sealer/porefiller. This has replaced the epoxy pore fill and paste type fillers I used previously. I do not use any polyester top coats but they would work much the same as this product. I instead use it as a base and run a variety of top coats over it.

Application schedule is tight, 20 minute gel time after catalyzing. Coats can be reapplied in as fast as 20 minutes. Or as long as 24 hours and still maintain a chemical bond. Cleaning up your gun and mixing equipment immediately with acetone is required. Accurate chemistry is also required, I mix all mine with a digital scale. A good respirator is mandatory, after seeing what this stuff does to the paint arrest filters in the booth you definitely don't want to breathe the slightest bit of atomized product.

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Brian

You never know what you are capable of until you actually try.

https://www.howardguitarsdelaware.com/

Brian, can you spray nitro over the poly sealer?

Yes. I run nitro, conversion varnish & 2K urethane over the polyester with great results.

_________________
Brian

You never know what you are capable of until you actually try.

https://www.howardguitarsdelaware.com/

I would not recommend gluing the bridge directly to the finish. I did this on several guitars and some have come back with lifting bridges. The bridge glues to the finish just fine but the finish does not adhere well enough to the wood and it was always the finish/wood interface that failed. It may be also be a result of the challenging climate in Canada where we have humid summers and dry winters. Anyway, now I always route off the finish and glue the bridge directly to wood.

Pat

_________________
There are three kinds of people:

Those that make things happen,
those that watch things happen,
and those that wondered what happened.

I would recommend this route as well. I have found that the clear coat on the polyester to be very unforgiving. Meaning, when wet sanding if you sand through to an earlier coat you will get "layering" that will not buff out, and must be recoated to fix. I am aware that the mix ratio can effect this, but with the goal of a thinner finish adding more clear because of overspending isn't ideal. I always feel like I cannot level the way I want to which makes to wet sanding process anxiety provoking. Also buffing the stuff takes much longer since it is a lot harder. However, I did like the sealer and will likely switch to a sealer/ 2k top coat process myself. It is also much more finicky about the spraying environment, it must be the right temp, the right humidity, and very clean. If you get "trash" in your top coat it seems to never really go away even after leveling and buffing.

Looking on advice on how to identify a poly finish vs a nitro finish. You would think I would know this by now but sometimes it is hard to tell.
Am thinking..find a spot say behind a tuner and see if lacquer thinner will dissolve it off easily?
Any advice..or suggestions? thanks..

I use acetone rather than thinner as it evaporates quicker but you got the idea.

_________________
Brian

You never know what you are capable of until you actually try.

https://www.howardguitarsdelaware.com/