Buffing polyurethane finishes

[kmanuele]

After a few builds, using a couple brands of water-base poly finish, I have found it very difficult to buff out sanding scratches. This material seems to be quite hard when cured.

I am using 3M's Perfect It auto polishing system, with RA polishing machines and by hand on neck. Maybe automotive clear coats are softer than these finishes?

I am pretty careful with leveling/sanding, using good brands (Norton Ice and/or Micromesh), and sanding up to 2000 grit (Norton) or 4000 (Micromesh).

It seems the compound provided in the first step of the Perfect It system is not aggressive enough.

Anyone with related experiences, or suggestions?

Thanks

[mirwa]

You really need a buffing wheel for these finishes, what you do by hand in a minute a buffer does in a second

[Bruce Sexauer]

+1 on the pedestal buffer. I got mine after 25 years of trying to get a professional finish by hand, and never got all that close until the the buffer arrived. There’s no way around it.

[charles Tauber]

Originally Posted by Bruce Sexauer

+1 on the pedestal buffer... There’s no way around it.

+2.

Based on my experiences - the difference between rubbing back and forth by hand vs. a powered buffer - I switched to an electric tooth brush (for my teeth, not guitars), for the same reason.

[cobalt60]

Can you clarify HOW you are using the 3m system? I like it very much, but the intended use is with those 6-inch-plus buffers.

I'm asking because if you're doing it by hand (no tools) then that system will NOT work - it relies on frictional heat.

[kmanuele]

Originally Posted by cobalt60

Can you clarify HOW you are using the 3m system? I like it very much, but the intended use is with those 6-inch-plus buffers.

I'm asking because if you're doing it by hand (no tools) then that system will NOT work - it relies on frictional heat.

I was unclear. I use a powered DA (dual action) buffing machine. I have a Porter Cable 6" machine but found it to be too large, so now use a 3" machine with 2" adapter for the waist and headstock. I only do the neck by hand.

Not sure your comment re: heat. Buffing/polishing materials are abrasives, and work by abrasion. Heat is an enemy. Nice thing about DA polishers is that you can't overheat the finish, unlike a rotary polisher in the hands of an amateur (me :-).

The Perfect It system has 3 components, the #1 being a compound, and #2 and #3 for swirl removal and polishing. I use yellow, white, and black foam pads respectively.

I start with #1, and after many passes (and lots of material), there are still some scratches remaining. Note that the scratches are most noticeable with a single light source, like the auto folks use.

The auto folks seem to get all scratches removed with only a few passes of the #1 compound, so I wonder what an auto clearcoat is vs. these poly finishes.

3M has a more aggressive compound in this series, which I may try -- as I like this system.

[Talldad]

Originally Posted by kmanuele

After a few builds, using a couple brands of water-base poly finish, I have found it very difficult to buff out sanding scratches. This material seems to be quite hard when cured.

I am using 3M's Perfect It auto polishing system, with RA polishing machines and by hand on neck. Maybe automotive clear coats are softer than these finishes?

I am pretty careful with leveling/sanding, using good brands (Norton Ice and/or Micromesh), and sanding up to 2000 grit (Norton) or 4000 (Micromesh).

It seems the compound provided in the first step of the Perfect It system is not aggressive enough.

Anyone with related experiences, or suggestions?

Thanks

I have finished several guitars recently with water based lacquer. All sanding levelling has been done by hand in the direction of the grain. I finish with micro mesh up to 1800,2400,3200,4000 then 6000.

Once that case hits 3 course of buffing medium, fine, extra fine, in the direction of the grain again I can hang it up in my bathroom and use it as a shaving mirror.

Hope that helps.

[mirwa]

Originally Posted by kmanuele

The auto folks seem to get all scratches removed with only a few passes of the #1 compound, so I wonder what an auto clearcoat is vs. these poly finishes.

It is the same stuff, difference is a caris not sanded after final coat to get a smooth reflective finish like a guitar is.

Have a close look at your car finish it has an orange peel effect to the finish which is simply buffed, the polish they use is not removing any scratches as they do not sand the final coat

[kmanuele]

Originally Posted by cobalt60

Can you clarify HOW you are using the 3m system? I like it very much, but the intended use is with those 6-inch-plus buffers.

I'm asking because if you're doing it by hand (no tools) then that system will NOT work - it relies on frictional heat.

I should clarify on foam pads. They have abrasive properties and are graded as such, with the harder ("heavy cut") pads used for compounding, and softer for polishing.

There are no standards to the color coding of the pads. 3M, Meguiar's, Menzerna, and others have the own color-coded pad sets for their buffing products. I use Lake Country pads, thus the yellow-black range I cited.

re: 6" buffers. Mine worked ok on fronts and backs, but over-hanged the sides so much that it shed buffing products onto the top and back (and me :-(). You can get 3" adapters, and pads, for those buffers.