Tip: Cutting and Buffing Paint

[cdeerinck]

Am I the only one that can't see any of the pictures on the first 3 or 4 pages of this post? I can see the pictures in the last few pages.

[snopercod]

You are not alone. DanH is looking for a new host for his photos.

[cdeerinck]

Originally Posted by Aluminum

Take a look at "engineered siloxane" resins such as PPG PSX 700 or Sherwin Williams XLE-80.

Aluminum -

I have a few Paint with Pearl pigments. I am ultimately hoping for a ghost blue pearl on white, and a metallic red. The SW metallics are not acceptable, as you need to shoot them from the base coat up in the same color, and my design has too many transitions to make that anywhere near affordable.

A few questions if you would not mind:
1) What do you suggest to use for a clear coat to shoot a ghost pearl over the XLE-80?

2) Do you know if SW makes a satin instead of a gloss white in the XLE-80 line?

3) What do you recommend as a actual source to buy the SW paints?

[Aluminum]

Originally Posted by cdeerinck

Aluminum -

I have a few Paint with Pearl pigments. I am ultimately hoping for a ghost blue pearl on white, and a metallic red. The SW metallics are not acceptable, as you need to shoot them from the base coat up in the same color, and my design has too many transitions to make that anywhere near affordable.

A few questions if you would not mind:
1) What do you suggest to use for a clear coat to shoot a ghost pearl over the XLE-80?

2) Do you know if SW makes a satin instead of a gloss white in the XLE-80 line?

3) What do you recommend as a actual source to buy the SW paints?

Ah, #1 is easy: nothing goes on top of polysiloxane except more of same! It's silly how slippery that stuff is once fully cured. The good news is it can later be recoated with itself without sanding, no loss of adhesion. It is extremely glossy as a topcoat and resists UV and chemicals better than polyurethane.

Sorry can't help with #2 and #3 as I never tried the SW version. I imagine any SW retail store should be able to order. PPG does have a semi-gloss version: PSX 700SG. I bought mine (high gloss clear) from here.

I tried a couple of interference pigments ("ghost pearls") in PSX 700 without success so far, but neither attempt was over black base. I'll do a proper test one of these days of untinted interference flakes over black and report what I find. Note that many pigments look different inside siloxane epoxies from their "normal" color inside acrylic topcoats or intercoats; I suspect different index of refraction of the resin, as opposed to chemical reaction. That might be what's ruining the interference effect. More research required.

I also tried PSX 700 clear over white Akzo epoxy primer (i.e. plain titanium dioxide tint), both applied with foam roller. After cutting and buffing this resulted in bright glossy white mirror finish shinier than any airplane at my home field. If you are not planning on metallics, have a lot of free time (roller deposits very thin coats) and don't mind wet-sanding the entire airplane twice, this could be an inexpensive and environmentally friendly way of getting a top notch finish that is lightweight and durable.

By the way, in case it's not clear from the manufacturer's instructions: siloxane epoxies stick to bare metal, no primer needed. Simply alodine and shoot pigmented then clear.

[cdeerinck]

Originally Posted by Aluminum

without success so far

Dan V,

I thought the ghost pears were to be mixed with clears, and shot over the base coat, not in it. At least that is what the Paint With Pearl page says (unless I am misreading it). Maybe that is causing the lack of success? That is why I asked about a clear coat.

If you were doing your plane with a pearl and using a clear coat, would you shoot PSX 700SG over the XLE-80, or would you do a tinted base of the PSX 700SG, and then shoot a clear coat over that?

[Aluminum]

Originally Posted by cdeerinck

I thought the ghost pears were to be mixed with clears, and shot over the base coat, not in it. At least that is what the Paint With Pearl page says (unless I am misreading it). Maybe that is causing the lack of success? That is why I asked about a clear coat.

Correct. So, the complete procedure would be:
- clean&etch
- alodine
- shoot black, wet sand if not flat
- shoot interference flakes or ghost pearl pigment--do not sand!
- shoot clear, wet sand and polish

The interference effect is relatively faint, the black base helps bring out the contrast. A light base overwhelms the colored reflection from interference flakes.

Originally Posted by cdeerinck

If you were doing your plane with a pearl and using a clear coat, would you shoot PSX 700SG over the XLE-80, or would you do a tinted base of the PSX 700SG, and then shoot a clear coat over that?

I wouldn't mix the S-W product with the PPG product. Although they are supposed to use similar chemistry it's not a given that they are compatible. Use the same resin for all coats. Alternatively, you can use any epoxy primer as first coat as the siloxane will keep it from chalking.

[DanH]

Re-posted photos.

[Aluminum]

Originally Posted by DanH

Re-posted photos.

Thanks Dan! Your thread raised the resale value of the RV fleet by a third.

[snopercod]

What Aluminum said! You photos and commentary really help us amateurs.

[snopercod]

DanH has put together a great thread here showing us all how it should be done. I'm just an amateur who hates painting, but maybe it would be useful for everybody if I posted a few examples of how it should NOT be done. First of all, your cutting and buffing will go a LOT better if you do a good job of applying the paint in the first place. In my case, I used a cheap Harbor Freight Binks-knockoff siphon gun, and really didn't have a good spray booth. Two strikes against me. There are a lot of tricks to adding the proper amount of reducer to the paint so that it will flow evenly without runs or sags with minimal orange peel. I guess I didn't know any of those tricks because I got all of the above. You won't get runs and sags if your workpiece is horizontal, but that is hard to do on a fuselage or if your aileron is hanging vertically from some wires so you can do both sides at once.

You will really want to minimize dust or other debris while spraying, so you should cover the floor of your spray booth with butcher paper or wet it down with a garden hose. You don't want to spray when it's windy. I didn't do any of those things with this last attempt, and here are the results:



The good news is that all those "dust nibs" (I think they're called) sanded out, but it took some time and effort. I should mention that I'm using single-state Urethane paint (Nason Ful-Thane) which seems to work pretty well for a klutz like me. I started with 800 grit to remove 80% of the defects, then switched to 1200 grit for the last 15%. Yes, this is not a show plane so I'm willing to accept an occasional defect here and there. After that, I went to 2000 grit wet-or-dry and that made the surface almost shiny, but I can still see some faint scratches. I bought some 3000 Trizact discs which I will be using tomorrow. After that, I intend to use 3M "Perfect-It" compound #1, then #2 if necessary.

One thing I've discovered is that a foam 3M hand pad cuts almost as fast as the DA sander, and doesn't leave swirl marks. This has been an adventure.