Help! Clear polyurethane spray can is beading on bare maple

[Stagelab]

Dry to the touch and ready to re-coat, and cured hard enough to sand are 2 different things. I'd look at fully cured tine for the product, wait that long, sand it with the 600 till it's flat. Shouldn't matter if you don't go all the way back to bare, just need a flat surface to keep building on.

I checked the manufacturer instructions and they don’t mention cure time. I found a Reddit post where someone said they read cure time was 3 days but no idea where they got that info. What would you do in this case?

The instructions say to sand with 220. I could do that instead of 600 but I thought lower grits would be too aggressive especially if I succeed in applying lighter coats.

Here are the instructions. https://www.rustoleum.com/~/media/D...Varathane_Crystal_Clear_Polyurethane_TDS.ashx

 

[Stagelab]

One pass from depression of the nozzle to release should be so quick that you can't even measure it, particularly for something as small as a headstock.

Trying to describe a physical motion in text, if the headstock was viewed vertically in front of you, you'd hold the can pointing to the left of the headstock outside of its outer edge, depress the nozzle and move to the right. Not even a second that you can measure. Then move down a tad and starting from where you are on the right, move back to the left with a barely-a-second time lapse. And so on, back and forth in a squared zig-zag pattern -- left to right, down, right to left, down, left to right.....

The coat that's left should barely be noticeable.

Let that sit for the hour the label recommends then repeat that barely-noticeable misting. It'd probably take about several repeats for it to start looking like a solid coat, visually. But stop after about 3 cycles and let it sit overnight. Come back to it in the morning and check out how it did. You may find that you can get away with more in a session, but start slower until you dial in your pattern. As you said, this is your first time using this particular product. You just need time to get to know it.

(plus environmental conditions where you are will also play a role)

Good stuff. I’ll follow this technique. What do you think about the time I need to wait before sanding between coats? Or are you suggesting I do a few of these light coats an hour or two apart and then let it dry overnight and sand the next day (edit: or to give it more cure time, sand a few days later).

 

[Stagelab]

I've never been handy with a rattle can or an air sprayer for that matter. I use coats Tung oil hand rubbed and buffed. I can do that without messing up. I can do frame carpentry but the finer exacting work... never comes out quite right.

I like tru oil for necks. With waterslide decals water based spray cans are recommended. Pretty sure oil based finishes will damage the decal though I’m sure results vary.

 

[Stagelab]

I've been refinishing guitars and basses for over 20 years. I'm not a fan of water base finishes. Most of the water base clears I've been around, are designed to be put over a base coat. IMHO water and wood just don't mix. Seems like a possibility for future delamination. As for your predicament, looks like too much material put on too fast.

I hear ya. I’ve never used water based before. Only reason I am is they’re recommended for waterslide decals. Guy who made the decal I have told me not to use oil based.

 

[Reedt2000]

I checked the manufacturer instructions and they don’t mention cure time. I found a Reddit post where someone said they read cure time was 3 days but no idea where they got that info. What would you do in this case?

The instructions say to sand with 220. I could do that instead of 600 but I thought lower grits would be too aggressive especially if I succeed in applying lighter coats.

Here are the instructions. https://www.rustoleum.com/~/media/D...Varathane_Crystal_Clear_Polyurethane_TDS.ashx

I know water-bourne poly cures faster than oil which needs quite a while, like a week to 3 weeks depending on the thickness of the build up. I've never worked with it so no direct experience. I'd try 3 days, then sand and see how it reacts. I agree that 220 is too aggressive, unless you have a lot to remove. I usually use 400-600 for flattening depending on exactly what I need to do. If I'm getting rid of runs or sags I'd use 400, just removing dust nibs or light orange peel more like 600.

 

[/\/\3phist0]

 

[Stagelab]

I know water-bourne poly cures faster than oil which needs quite a while, like a week to 3 weeks depending on the thickness of the build up. I've never worked with it so no direct experience. I'd try 3 days, then sand and see how it reacts. I agree that 220 is too aggressive, unless you have a lot to remove. I usually use 400-600 for flattening depending on exactly what I need to do. If I'm getting rid of runs or sags I'd use 400, just removing dust nibs or orange peel more like 600.

You think I need to sand between every coat? Cause that’ll take ages.

 

[Reedt2000]

You think I need to sand between every coat? Cause that’ll take ages.

Not every coat. When I've finished maple necks and other basses projects with poly, I've taken a day on the weekend and starting in the morning add coats every couple hours (waiting the manufacturers recommended time between them). Then I'll let it sit a week, very lightly sand to add texture, remove dust nibs, and do it again. Continuing until I get the build up I want. If I got a run or other major flaw in it, I wait till it's cured (with oil based that is usually until it doesn't smell like poly anymore), sand the flaws out, and start the process again. It takes patience and time, but that's what has produced good results for me.

 

[Stagelab]

Not every coat. When I've finished maple necks and other basses projects with poly, I've taken a day on the weekend and starting in the morning add coats every couple hours (waiting the manufacturers recommended time between them). Then I'll let it sit a week, very lightly sand to add texture, remove dust nibs, and do it again. Continuing until I get the build up I want. If I got a run or other major flaw in it, I wai till it's cured (with oil based that is usually until it doesn't smell like poly anymore), sand the flaws out, and start the process again. It takes patience and time, but that's what has produced good results for me.

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Your work looks great.

The headstock is smooth to the touch now, including the area I circled in that pic.

Correct me if I’m heading in the wrong direction but since the decal isn’t going where that circled area is, is it fine to apply the decal next, then after it dries start misting coats with dry time in between, and after giving it ample time to cure, sanding it down some. Then add more coats and sand again till I’m happy with the results.

Lots of folks here suggested going back to bare wood but I don’t want to do that unless it’s needed.

Edit: a friend who has done decals just told me after applying the decal and then applying many more coats of clear, and sanding at the end, the uneven area will resolve itself. This is just his take ymmv.

 

[Reedt2000]

I might throw one thin coat on now and see if your circled area blends in with the rest of it. If it does, then I think applying the decal (after at least 24 hours dry time) and starting the build up process again should be fine.

If it doesn't, then taking 220 and sanding back to bare might be needed to get rid of that spot.

Welcome to the wonderful world of amateur refinishing. There can be plenty of "a couple steps back" moments. But they are all learning opportunities

 

[Thumpin6string]

I hear ya. I’ve never used water based before. Only reason I am is they’re recommended for waterslide decals. Guy who made the decal I have told me not to use oil based.

Regular poly or any catalyzed urethane is fine over decals. Not too sure about Tung oil or Truoil. Evan lacquer would work or an acrylic clear. I only use catalyzed urethane for my refinishing, but I have pro spray equipment. If you have no ability to spray with a gun, I'd recommend a regular poly in a spray can. They actually make catalyzed urethane in a spray can for automotive paint repair. It would work great for a bass neck or body.

 

[Stagelab]

Regular poly or any catalyzed urethane is fine over decals. Not too sure about Tung oil or Truoil. Evan lacquer would work or an acrylic clear. I only use catalyzed urethane for my refinishing, but I have pro spray equipment. If you have no ability to spray with a gun, I'd recommend a regular poly in a spray can. They actually make catalyzed urethane in a spray can for automotive paint repair. It would work great for a bass neck or body.

Since the guy who makes and sells the decals recommended water based I’m gonna stick with it. If it doesn’t pan out, I can try again with oil based poly or catalyzed urethane.

 

[Low Main]

Initial sprayed coats, whether aerosol or with a gun, sometimes have a hard time wetting out a bare wood surface. Especially with water based material. I like to apply an initial thin wetting coat by hand, either by pad or brush. I sand that level, and then subsequent sprayed coats lay out well. The wetting coat doesn't have to be water based. It can be Zinsser Seal Coat or another solvent based sealer. But not lacquer sanding sealer, which typically has stearates in it.

I've never sprayed by timing. I've always just gone by rate and distance of spraying motion and appearance of the sprayed film. Methodically flowing the wet edge.

I sand between coats of water based material, as subsequent coats don't really bite in to prior coats the way that lacquer does. That goes for both water based lacquer and urethane.

If I want water based material to bite in, I add a bit of denatured alcohol when spraying it with a gun.

Water based coatings usually sand well, but water based finishes are so readily softened by solvents that I would just wipe the faulty finish off with lacquer thinner instead of sand it down, and then start over.

I just went back and looked at the headstock photo again. It looks like the material is fisheyeing. There may be a contaminant on the wood. Water based finishes can be tough to apply from a surface tension standpoint. They don't lay out as readily as solvent based finishes and are fussier about the condition of the surface they're being applied to.

If you sanded the bare wood with a stearated sandpaper like 3M Fre-Cut, that will leave residual stearates on the wood and a water based finish will not like it, and will not lay out or adhere well. If I sand with a paper like Fre-Cut, I wipe the wood down with alcohol or lacquer thinner before applying the finish. I learned that the hard way and was lucky to know a 3M chemist (and woodworker) who I could call for guidance on things like that.

In general, water based coatings cure to a softer and less durable film than solvent based coatings, so the thinner the overall final finish, the better.

 

[Stagelab]

Initial sprayed coats, whether aerosol or with a gun, sometimes have a hard time wetting out a bare wood surface. Especially with water based material. I like to apply an initial thin wetting coat by hand, either by pad or brush. I sand that level, and then subsequent sprayed coats lay out well. The wetting coat doesn't have to be water based. It can be Zinsser Seal Coat or another solvent based sealer. But not lacquer sanding sealer, which typically has stearates in it.

I've never sprayed by timing. I've always just gone by rate and distance of spraying motion and appearance of the sprayed film. Methodically flowing the wet edge.

I sand between coats of water based material, as subsequent coats don't really bite in to prior coats the way that lacquer does. That goes for both water based lacquer and urethane.

If I want water based material to bite in, I add a bit of denatured alcohol when spraying it with a gun.

Water based coatings usually sand well, but water based finishes are so readily softened by solvents that I would just wipe the faulty finish off with lacquer thinner instead of sand it down, and then start over.

I just went back and looked at the headstock photo again. It looks like the material is fisheyeing. There may be a contaminant on the wood. Water based finishes can be tough to apply from a surface tension standpoint. They don't lay out as readily as solvent based finishes and are fussier about the condition of the surface they're being applied to.

If you sanded the bare wood with a stearated sandpaper like 3M Fre-Cut, that will leave residual stearates on the wood and a water based finish will not like it, and will not lay out or adhere well. If I sand with a paper like Fre-Cut, I wipe the wood down with alcohol or lacquer thinner before applying the finish. I learned that the hard way and was lucky to know a 3M chemist (and woodworker) who I could call for guidance on things like that.

In general, water based coatings cure to a softer and less durable film than solvent based coatings, so the thinner the overall final finish, the better.

Good info to know.

I’m guessing you can’t spray poly into a cup and brush it on? I don’t have any brush on varnish.

Do you mean to apply denatured alcohol with a rag before brushing the first coat? Then spray the additional coats? Or are you saying to apply alcohol after every time you sand?

At this stage in my process I’m moving forward cause I am prone to analysis paralysis and for me there tend to be diminishing returns when I get so much different input.

I didn’t sand to bare wood. Applied a mist coat this morning to see if it’ll fill in the uneven area. I’m gonna sand after 24 hours dry time, then plan to apply the decal.

 

[Stagelab]

A few things here -

I have never heard of oil based poly being harmful to decals. Solvent based, yes, but oil based should be fine. I guess if the guy who made the decal says so I would believe him, it's just not typical.

Sand it down to bare wood and then some. Looks like you have a few things going on:

Possible contaminate in the wood - if there was an oil based finish previous, then some vestiges of the finish might remain. I'd be safe and sand it down bare and start over. Definitely, at the very least, get rid of all of the orange peel and bubbles

It looks like you much used more paint than needed; the advice above around quick mists is great. Don't get too heavy, use quick bursts. Also, orange peel and bubbling can happen when you spray fresh poly over uncured poly. This screws the underlying paint as well, so again, you'll need to sand to bare wood. What does the manufacturer say about recoats? With most paints you can recoat within a few minutes, but the environment (temp and humidity matters).

Some spray paint (Rust-Oleum looking at you) specify that you either recoat within an hour or you need to wait 48 hours. If you ignore that and try and recoat in five hours,or even wait a day, your paint will bubble and peel and you'll need to start over.

You don't have to sand between coatsif you do a light misting and you do several coats within the recommended time frame, but if you do, check what the manufacturer says. You should sand if you wait for the paint to dry (whatever time the manufacturer says). It may seem counter intuitive, but smoother grit (400-600) can actually show fine scratches while 200 grit the scratches will "melt" into the top coat. Water based poly is less forgiving than oil based.

Instructions say to allow finish to dry one hour before recoating. Unclear if that means you can’t wait longer. It says to sand lightly with 220 between coats. That grit seems aggressive. Are you saying I should use 220?

Everyone but the decal maker is saying oil based poly is fine with decals and easier to work with. If water based poly spray cans are problematic for this purpose, then even if I sand bare and start over I’ll bet I’ll run into issues. Orange peel etc. is working with oil much easier and more successful? I’m a beginner and I don’t want my first ski run to be on a black diamond.

Not sure which finish was used on the headstock originally. Tried to find out but never got an answer from the manufacturer.

 

[Low Main]

It's tough to get a lot of input from different angles in the midst of a procedure. I almost didn't post because of that.

I've never sprayed aerosol into a cup and applied it by hand but I've seen people do it. I can't remember what the results came out like.

It doesn't take much to wet out a bare wood surface. With water based finish, you could lightly pre-wet the wood with distilled water and that might do the trick instead of having to pad or brush on a sealer coat before spraying. Just padding it on with lint free paper towel.

Yes, wipe the bare wood after sanding with denatured alcohol to remove stearates as best as possible.

But don't wipe down a sanded coat of finish with denatured alcohol. The alcohol will bite into the applied finish and make a mess of it. Drug store isopropyl alcohol wouldn't bite in as aggressively but a lot of "rubbing alcohol" has lanolin in it, which you don't want.

I haven't had a lot of satisfactory success filling in uneven finishes. Emphasis on the word satisfactory. I can get it done but the process is not rewarding. I'm fortunate to have a spray room, so I can airbrush problem areas if needed.

That's where you might want to spray some finish into a cup and brush it on the area with an artist's brush.

Chasing finish problems around a workpiece can get truly frustrating. It seems like several folks have suggested going back to bare wood. That's what I would do, especially since lacquer thinner removes water based finishes so readily. I pad it off with paper towel. No scraping needed. And when you get down to bare wood, the residual amount left in the pores is your sealer coat.

In general, you can always test a bare wood surface by flicking a few droplets of water on it. If the water soaks right in, you're good to go. If the water beads up, you need to prep the surface, whether by sanding or a solvent wipe down. We routinely flick test veneer because we don't know how compressed or burnished the wood fibers are after the slicing process. We almost always have to scuff sand the gluing surface of the veneer before gluing it down.

 

[Stagelab]

It's tough to get a lot of input from different angles in the midst of a procedure. I almost didn't post because of that.

I've never sprayed aerosol into a cup and applied it by hand but I've seen people do it. I can't remember what the results came out like.

It doesn't take much to wet out a bare wood surface. With water based finish, you could lightly pre-wet the wood with distilled water and that might do the trick instead of having to pad or brush on a sealer coat before spraying. Just padding it on with lint free paper towel.

Yes, wipe the bare wood after sanding with denatured alcohol to remove stearates as best as possible.

But don't wipe down a sanded coat of finish with denatured alcohol. The alcohol will bite into the applied finish and make a mess of it. Drug store isopropyl alcohol wouldn't bite in as aggressively but a lot of "rubbing alcohol" has lanolin in it, which you don't want.

I haven't had a lot of satisfactory success filling in uneven finishes. Emphasis on the word satisfactory. I can get it done but the process is not rewarding. I'm fortunate to have a spray room, so I can airbrush problem areas if needed.

That's where you might want to spray some finish into a cup and brush it on the area with an artist's brush.

Chasing finish problems around a workpiece can get truly frustrating. It seems like several folks have suggested going back to bare wood. That's what I would do, especially since lacquer thinner removes water based finishes so readily. I pad it off with paper towel. No scraping needed. And when you get down to bare wood, the residual amount left in the pores is your sealer coat.

In general, you can always test a bare wood surface by flicking a few droplets of water on it. If the water soaks right in, you're good to go. If the water beads up, you need to prep the surface, whether by sanding or a solvent wipe down. We routinely flick test veneer because we don't know how compressed or burnished the wood fibers are after the slicing process. We almost always have to scuff sand the gluing surface of the veneer before gluing it down.

Is the order of operations to sand to bare wood, then apply denatured alcohol, then apply sealer coat (distilled water or brush on poly from my spray can), then a few mist coats with an hour dry time in between, then let cure before sanding?

How much orange peel is expected if this is done well?

I read about all the factors that can lead to orange peel. Lots of possibilities. Seems very difficult to control for them, even if I manage to mist truly light coats from the “right distance” away.

 

[Low Main]

I don't have any experience with waterslide decals over an oil based urethane, sorry to say.

If you go with an oil based product, it's best to let the last coat before the decal cure as long as you can. Days at least, to let the solvents outgas from the curing finish. The longer you wait, the less likely having problems with the decal will be.

It takes much longer for solvent based finishes to evacuate all their solvent vapors than many folks realize.

 

[Stagelab]

You should have zero orange peel if done correctly. If you get orange peel, you have to get rid of it.

Ok. I’m trying to reconcile lots of input here and it’s getting a bit overwhelming.

Is the order of operations to sand back to bare wood, then apply denatured alcohol, then apply sealer coat (spray my poly into a cup and brush on with clean rag), then a few mist coats with an hour dry time in between, then let cure before sanding (220 as recommended in poly can instructions)?

If not, what would you modify here?

Thanks for the hand.

 

[Stagelab]

If instructions say to wait an hour, wait an hour then recoat. Some paint (especially poly in a rattle can, and again I'll call out Rust-Oleum) is sensitive to recoat times. If it says and hour, wait an hour and recoat. I've seen many, many paint jobs with rattle cans get screwed up because the instructions say to wait an hour OR 48 hours to recoat - they try to apply in 24 hours and the paint gets screwed up because you have to wait 48 due to the curing and outgassing.

Paint adheres to a surface in one of two ways - chemical binding or physical bonding. The only reason that you would need to sand in between coats is if the paint is not level/flat/smooth or if you need to get the paint to adhere to the previous coat after the previous coat dries. That's it. Do the instructions from the manufacturer say to wait an hour and then sand? When you sand, you should get a fine powder, it should not gum up the sandpaper.

220 is not aggressive, especially when sanding lightly.

I think you are making more work for yourself than needed. Ask yourself this - does every bass and guitar manufacturer out there go thru this whole rigamarole whenever they apply a decal, or do they spray, wait for it to dry, apply the decal, then spray a top coat?

Instructions from the decal maker say to apply a varnish to the surface before applying the decal and to sand the surface first to ensure it’s smooth. The one hour wait before recoating is from the poly instructions which say nothing about when to sand, just a recommended grit.

I don’t think I’m making this more complicated. I’m reconciling a ton of feedback and when you get a ton of feedback, it’s inherently a little complicated. I’m doing the best I can.

So is the order of operations I posted aligned to what you are recommending?