Need some wet sanding clear coat advice.

[Rob J]

I'm in the middle of refinishing a guitar. Base paint is on and I have applied 3 coats of clear coat and started wet sanding. I started with 800 grit to get the surface free of orange peel but when getting to where the orange peel is gone I started seeing traces of the base color in my sandpaper. This indicates that I've sanded through the clear coat and reached the paint. I'm not applying a lot of pressure and yet still seem to be going too deep. Maybe I didn't apply enough coats of clear coat?

At this stage, after getting the surface smooth I am reapplying clear coat to try again because it didn't make sense to continue wet sanding with the next grade of paper if I'm through the clear coat. How far do you sand with the coarser grade of paper before going to the next finer grit? Do you take the surface to where there is no orange peel with the first grit or do you just sand so far and let the successive grits do the job? This is all new to me.

So far I've put on another 3 coats of clear but should I do 4 (or more) to avoid sanding through again? I don't want to go through the sanding process again only to have the same thing happen.

How may coats of clear coat is enough? How many is too many?

 

[eallen]

Are you talking nitro?
Stop and spray on more clear.

Some will say practice until you get no orange peel, which is ideal. At the same time, that takes years for many without specific hands on coaching. Some never get the technique down to do so.

There is no need to move to the next finer grit sanding until you have your surface level from the initial grit. If you are spraying nitro, doing the last couple coats as flood coats can help get a nice smooth finish within reason. Don't expect a miracle if the previous layers are reallly bad.

When you talk about coats, a coat is generally seen as 3 passes per coat. There are maybe some who get by with 3 coats total but that is not my experience or preference. I like the depth of look of a little thicker clear and will do 6-7 with the last 2 as flood coats.

Dont get discouraged. We all start somewhere! Mistakes are the great educator of those who try again.

Look forward to seeing some pics of the project!

Eric

 

[telepraise]

Eallen's advice is superb. Nitro burns in to the underlying coats so you can lay down as many coats as you want before sanding. If you're shooting from a gun, you need to increase the amount of retarder/flowout enhancer so your coat flows out before it goes off and maintain a wet margin on your passes. If you're rattle canning I don't know what to advise you as I've never wrestled that beast. I'm sure others who have will come forward. So many variables come into play, it's hard to diagnose what's causing orange peel in your case.

 

[Rob J]

Sorry, should have specified paint and method. Not nitro. I'm clear coating with rattle can Rustoleum over paint of same brand. I know that rattle can painting is not ideal but it's all that I have to work with and I know that some folks get excellent results with rattle cans. The orange peel that I get is not excessive and easy enough to sand out. I just don't want to sand through to the paint again. So from what has been said so far, I'm thinking that I just don't have enough layers of clear coat. I'll shoot on a couple more before sanding again. I may not end up with an expert job but I'm learning a lot in the process.

 

[dsutton24]

Rattle cans are fine. Lots of people have excellent results with aerosol paint, myself included.

The problem is the clear coat you used, and the thickness of the clear coat. If you manage to get a smooth finish, there's no need to sand. Since you got orange peel, you need to sand to get a smooth surface. The more you need to sand, the thicker your clear coat needs to be. It all goes hand in hand.

If your clear coat is some kind of poly, wet sanding will probably leave witness lines, google that term if you're not familiar with it. Sometimes witness lines can be buffed out, but usually they're going to stay no matter what. I've never gotten a really good finish with poly, I'm sure there are others who have and can give you some useful information.

Keep plugging at it. I couldn't tell you how many paint jobs I did before I got one that I didn't want to throw rocks at. 'Course, I'm a ham-fisted hacker.

 

[boneyguy]

The first question I have is what are you using for a lubricant for your wet sanding? How often are you rinsing/cleaning/replacing the paper? What are you using as a backing block...how hard is it?

Also, what you should be using as a guide for the wet sanding is there should be no shiny spots left.....the whole guitar should be an even, matte finish.....shiny spots indicate a low area that hasn't yet been touched by the paper......the purpose of wet sanding is to level the paint and that's how you judge whether it's been completely leveled....no shiny spots.

So the long and short of it is if you're sanding through then: 1) you need more coats of clear. 2)you need to lighten your touch when sanding 3) you need to adjust your spray technique so the paint goes on smoothly and does a lot of the leveling on it's own so not so much sanding is required.

It does take practice and like someone else mentioned there's no way to learn how to do it without making mistakes.

 

[Rob J]

I'm using water with a bit of dishwashing detergent and cleaning as I go. For the flat area I used a block of half inch pine but only for the flat areas and not with much pressure. I HAD it down to completely smooth with 800 grit but as I've said, I started seeing paint tint in my sandpaper. I think the clear coat just needs to be thicker and maybe applied a bit heaver. I don't want to risk runs so have been hesitant to spray too heavy though.

 

[dan40]

I usually know when when to stop when I can feel the sanding block start to drag and want to stick. This means I have leveled the surface flat and the surface tension of the water is trying to grab at the sanding block. Then I move onto the next grit and repeat.

 

[boneyguy]

I'm using water with a bit of dishwashing detergent and cleaning as I go. For the flat area I used a block of half inch pine but only for the flat areas and not with much pressure. I HAD it down to completely smooth with 800 grit but as I've said, I started seeing paint tint in my sandpaper. I think the clear coat just needs to be thicker and maybe applied a bit heaver. I don't want to risk runs so have been hesitant to spray too heavy though.

I don't know that you need to spray heavier coats, probably just more coats. That being said, it is possible to spray too lightly. You want enough paint in a coat that it looks wet.

The problem you're running into is exactly why production guitars like Fender, Gibson, Ibanez etc. spray lots of clear over the colour coats....it's far more cost effective to spray more clear than it is to sand through and have to strip, sand and re-paint. If you get enough clear on you can have a drunken monkey wet sand successfully.....or a hungover, distracted and disinterested human employee.

 

[jvin248]

.

One hint is after you spray on (perpendicular to the surface) that 'thick clear coat' you put the guitar handle (the stick screwed to where the neck goes) in a PVC pipe clamped in a vice or screwed down to the bench. That way the clear coat will flatten better as it cures. Drips will be down the sides and on the back edges if you have anything. I'll partially level the peaks and then put a few more coats on to fill the valleys rather than try to scrub the mountains down to the chasms. It also needs to cure several days before sanding.
.

 

[eallen]

As Boneyguy said, it is not heavier coats but more. Multiple well done thin coats are far better tham a few heavy every time. The only heavy coats I do are the last couple as flood coats to get as closs to buff ready finish as possible. Heavy coats can extend your cure time significantly. If runs regularly occur on a spray job it is going on too heavy.

 

[philosofriend]

"Coat" is not a very scientific measurement. If your last color coat is not perfectly smooth, you are going to need a whole lot of clear before you start sanding. Also don't start sanding until you can put your nose right on the guitar and not smell any new paint smell. The paint shrinks as solvents escape so if you sand it smooth, then solvents leave, scratches and bumps will appear! If at all possible, weeks are better than days.

If your color is just a simple and opaque (no metallic, pearl, metalflake or candy) then you can sometimes survive a bit of sanding into the color without having to spray another color coat.
Spray more clear and if the sanded areas don't look splotchy when viewed from all angles, you are good to go. If it is splotchy, you might as well sand the whole mess flat before spraying more color. Hopefully Rustoleum has made colors and clear able to stick to each other in any combination. (Leading to another painter's slogan: "When you find by agonizing experiments a brand of finishes that work for you, stick to that brand.")

Now you know one reason why metallics are considered advanced finished work.

 

[rich815]

I’ve also learned the hard way with both Rustoleum and Krylon rattle cans that spraying clear coat too soon results is crinkling of the underlying color coat. The can might say dry in a week but it’s not dry enough for clear coats! I’m going to give my latest project a full dry for 3 weeks before I make another attempt with clear coat! So sick of sanding down and respraying! Argh!

 

[Silverface]

I'm clear coating with rattle can Rust- Oleum over paint of same brand

Rust- Oleum is a brand - not a product. They make (in aerosol form) oil based enamels, water based enamels, hi-heat coatings, textures, metallics - and lacquers, among more than a dozen individual types of aerosol coatings.

If you are using something like the Painter's Touch oil based enamel, I can tell you from working for years in Rust-Oleum tech support that it does not wet sand well. It was designed for it. eallen's lacquer advice would still apply - practice application in VERY thin coats (3 passes per coat works with enamels as well) and eliminate the orange peel.

But specifically - which Rust-Oleum color and clear coats are you using? Some require very different techniques; none but lacquer would I recommend for a durable guitar finish, but it seems that decision was already made.

Advice given by others may be good or irrelevant. We won't know until we know exactly what you're using.

PS - "coats" isn't really relevant. What's important is how thick the coating is going on as applied, and calculating the dry film thickness based on the solids by volume. You can measure wet film thickness with a $5-10 credit-card size gage you can find online.

Spray technique varies so widely there is virtually no way to estimate "how many" are enough. Even painters with decades of experience usually guess wrong when measuring thickness by eye. That being said, with good technique requiring no sanding of the clears 4-5 light coats of oil-based clear is a ballpark average. If there's orange peel and it HAS to be sanded there's just no way to know, which is why sand throughs are common.

 

[Rob J]

Thanks to all of the responses so far. You guys are really helping me out and I'm learning some things.

"I’ve also learned the hard way with both Rustoleum and Krylon rattle cans that spraying clear coat too soon results is crinkling of the underlying color coat.'

I have noticed some light crinkling happen in a couple of spots. I will take your advice to heart. I plan to sand these spots out and reapply.

@ Silverface - great to have someone here with first hand experience with Rust-Oleum products. The included photo is what I'm attempting to use. If this IS NOT the right product then I will sand smooth and start over if necessary. I truly hope that will not be necessary but I'll do it if I have to.

 

[rich815]

That’s the same stuff ^^^ I’m using (but apple red!) for my latest strat project. I did an earlier job using a similar product from Krylon ColorMaster ColorMaxx (Italian Olive) and using Rustoleum’s clear coat on top of that and all came out really good (not perfect but good, see below). I’m guessing the Rustoleum just takes longer to dry so I’m going the 3 weeks as mentioned before attempting a few coats of clear coat.

image removed image removed

 

[Silverface]

I have noticed some light crinkling happen in a couple of spots.

There are actually two common causes - 1) applying a coat before the previous coat is dry, or 2) applying a coat too thickly.

As far as these being the "right" products, only you can decide. I spent almost 40 years total in coatings tech support, training, lab and field support etc - here's just my quick take on the most used systems:

Enamels (like Painter's touch)- You can get a decent looking paint finish; it will not have the same gloss, color retention/non-yellowing properties, solvent resistance or durability (scratch, abrasion and impact resistance) of lacquers, polyurethanes or polyesters. Essentially, they have a much shorter service life and appearance deteriorates more rapidly.
But they are much simpler to apply. Note: "simpler" - not "easier". It's actually more difficult to get a smooth, glossy finish but conditions are bit more flexible, they're less flammable and somewhat safer.

Polyurethanes are nearly as easy to apply, but the fumes are more hazardous. Longer lasting than enamels. Tougher to fix if you make a mistake - very tough to sand and more difficult to apply smoothly than lacquers. Poor touchup and repair qualities. Excellent durability and solvent resistance.

Lacquers are a bit more difficult to apply and require more attention to safety policies. The actual application process is fastest - they dry quickly & each coat melts into the previous one, creating one solid coating system. When applied properly the entire coating and buffing process can take just a few days. The "melting" also makes them easiest to touch up and repair. Tighter working conditions (temp & humidity). More variety in color options. IF you DO have to wet sand it's an easier process.

There's not the time (or room) to provide full instructions for any of them. For polyurethanes look at manufacturer's web pages. For lacquers start with the Guitar ReRanch site's "basic finishing" - but all of that is bare-bones, basic stuff. Read a LOT.

And no matter what you end up using - even if you stick with "paint" - prepare, coat and buff scrap wood until you have perfected the process. Make your mistakes and learn on wood that doesn't matter. Figure out how to fix things, ask questions, and learn using practice work so you *don't* end up having to strip the real thing. (again...).

good luck

 

[Rob J]

In my ongoing research I just discovered Micro Mesh. Other than it lasting longer, are there any other significant benefits to using MM over regular wet dry sandpaper?

 

[bullfrogblues]

Another point that has not been mentioned here, but ad nauseum in other threads, "Always practice on scraps if you are unsure of the outcome"
It's so much easier to throw away a test scrap than to have to sand back and start over on your main project several times.
I get in a hurry, too, and want to get the project done, but I've learned the hard way too many times.

 

[Silverface]

Other than it lasting longer, are there any other significant benefits to using MM over regular wet dry sandpaper?

It comes in much finer grits, is more consistent, doesn't need a block because of the built-in pad (sanding without blocks - hard foam in different sizes and some with inside or outside curves - is a bad idea), and is washable/reusable. When I was doing other types of finish work that required sanding and a ton of relic work (guitar parts otherwise shouldn't require much sanding at all if the materials are applied correctly) I'd used various pads for up to an hour a day. I still have the original set I bought about 9 or 10 years ago plus one newer set.

For sporadic finishers they're a one time investment if you keep them clean.

Another point that has not been mentioned here, but ad nauseum in other threads, "Always practice on scraps if you are unsure of the outcome"

The following is 2 posts up from your comment:

And no matter what you end up using - even if you stick with "paint" - prepare, coat and buff scrap wood until you have perfected the process. Make your mistakes and learn on wood that doesn't matter. Figure out how to fix things, ask questions, and learn using practice work so you *don't* end up having to strip the real thing. (again...).