Help! Clear polyurethane spray can is beading on bare maple

[Stagelab]

Before I answer can you link to the product or instructions that you are using?

Reposting the poly instructions. https://www.rustoleum.com/~/media/D...Varathane_Crystal_Clear_Polyurethane_TDS.ashx

Decal instructions attached. I got extra guidance from the decal maker via email. He advised I use only a water based varnish and OK’d the Varathane.

 

[Stagelab]

Also just FYI, paint from a rattle can is just paint, there's nothing magic about it, however it's pretty thin and it likes to run. If you're gonna spray it in a cup and then brush it, be prepared for that. That being said, if silicon is your contaminate, then the easiest/best way to address it is to spray in a cup and add a drop of fish eye preventer.

Are you saying it’s gonna create a mess spraying it into a cup? Or that it’s gonna be hard to brush on since it’s so thin?

On another note, do you think this trick would help for when I spray onto the wood directly, to avoid it applying too thick? Read it on another forum.

“If you stand the rattle can in a tub of hot water (tap water hot, not boiling) for a few minutes before spraying it warms up the paint and thins it.”

 

[Low Main]

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?

You may be able to spray some finish into a cup, thin it with distilled water, and then pad that on as a thin wash coat on bare wood. I get better control from padding than a brush on small irregularly shaped surfaces like a headstock.

Doing mist coats may result in a bumpy surface, but leveling a nubby surface with sandpaper is easier than dealing with orange peel and fisheye. If you make methodical sweeping passes and watch the moving wet edge, you should be able to apply a nice coat that's wet enough to flow out well, but not too wet and thick so that bad things start to happen like runs and sags.

There may be good videos of people spraying guitars or furniture so you can see the steady sweeping motion they use. I don't watch how they spray in a guitar factory, because the sprayer often waves the gun around in a non-methodical way that I wouldn't do. It just doesn't look orderly or thorough. In factories, they may have flowout additives that help them achieve a nice coat even if they look like they're spraying haphazardly.

With orange peel, an important factor is temperature. I've pre-warmed workpieces before spraying them and if I'm using an aerosol finish and I have a chance to warm up the spray can, I always try to do that. I'm sure there are chats online about warming up aerosol cans.

Yes, I do know a person who decided to warm up some automotive aerosols on top of his woodstove and he ended up having a spectacular afternoon. It was like grandma's root beer in the cellar. Baboom.

 

[Stagelab]

You may be able to spray some finish into a cup, thin it with distilled water, and then pad that on as a thin wash coat on bare wood. I get better control from padding than a brush on small irregularly shaped surfaces like a headstock.

Doing mist coats may result in a bumpy surface, but leveling a nubby surface with sandpaper is easier than dealing with orange peel and fisheye. If you make methodical sweeping passes and watch the moving wet edge, you should be able to apply a nice coat that's wet enough to flow out well, but not too wet and thick so that bad things start to happen like runs and sags.

There may be good videos of people spraying guitars or furniture so you can see the steady sweeping motion they use. I don't watch how they spray in a guitar factory, because the sprayer often waves the gun around in a non-methodical way that I wouldn't do. It just doesn't look orderly or thorough. In factories, they may have flowout additives that help them achieve a nice coat even if they look like they're spraying haphazardly.

With orange peel, an important factor is temperature. I've pre-warmed workpieces before spraying them and if I'm using an aerosol finish and I have a chance to warm up the spray can, I always try to do that. I'm sure there are chats online about warming up aerosol cans.

Yes, I do know a person who decided to warm up some automotive aerosols on top of his woodstove and he ended up having a spectacular afternoon. It was like grandma's root beer in the cellar. Baboom.

Is distilled water by itself as effective a sealer coat as poly brushed on? Cause if so, that’s easier.

 

[Low Main]

Water won't size or seal the wood. It will just wet it and eventually evaporate. You need to apply some finishing material to seal the wood.

But if you wet the wood and then spray a thin coat while the wood is still wet, it's sort of like applying a thinned sealer coat. I've never done it that I can remember, but I would certainly try it if I needed to.

After a thin sealer coat, sand lightly so you don't sand through the sealer and re-expose any bare wood.

 

[Stagelab]

Water won't size or seal the wood. It will just wet it and eventually evaporate. You need to apply some finishing material to seal the wood.

But if you wet the wood and then spray a thin coat while the wood is still wet, it's sort of like applying a thinned sealer coat. I've never done it that I can remember, but I would certainly try it if I needed to.

After a thin sealer coat, sand lightly so you don't sand through the sealer and re-expose any bare wood.

I see. If I’m gonna sand back to bare wood, do I need to wait for it to cure first? No idea what the curing time is for this poly. I don’t have any thinners so was gonna sand.

 

[Brian Patterson]

I might be a little late on this, but as a woodworker using a wipe-on technique offers maximum control of finishing bare wood with poyurethane. Thin coats with a high grit sand in between allows a nice build of layers - I even use the poly WITH sandpaper after the first coat to create a super smooth surface. Finish with a wipe-on only coat or brush on for a gloss finish.

 

[Stagelab]

It creates a little mess, but it's not bad. I'd recommend wearing gloves (of course, you should always wear gloves when painting), but I use these little plastic Mardi Gras cups to spray paint in when and it works fine. The thinness that I was referring to was when you apply it - it won't apply like "normal" paint, it tends to run and drip, so take that into consideration if/when you apply it with a brush, and the standard advice on thin coats being better than thick coats applies. The other thing that you want to watch for is drips/runs as it dries - if you brush it on, try to keep the surface as level as possible.

And yes, the old "rattle can in warm water" trick works great if the environment is cooler/cold, but it +80 degree F temps, it's not needed and can even make things worse, especially if you over shake.

This is excellent advice here. Much of the success for painting is proper surface preparation.

This is what I would do (and have done in the past):

HUGE caveat here is that most of my experience is with oil based poly, but the principles should apply, along with the manufacturer's instructions. I've used water based poly before, just not on guitars.

Stri[p it down to bare wood. Sanding is good, sanding plus a chemical solvent is better as the solvent will remove traces of contaminates. After you get down to the bare wood, check the surface like @Low Main says with a few drops of water. If the water still beads, you still have an issue with the wood surface - most commonly, this is silicon from furniture polish or other wood treatments.

I use naptha to clean the wood, I find that it does a better job than alcohol does, but I don't think alcohol is a bad idea either.

If it's silicon (or even deep soaked grease, oil, etc.), you need fish eye eliminator - something like this - Fish Eye Eliminator Pint

Keep in mind that if you are brushing a light coat on (which you will need to do with fish eye eliminator) then the dry time is 2 hours - not one.

If the water does not bead, you're good to go. Sand it smooth - since the instructions say 150 grit, I'd go with 150 grit, although I typically use 220 with oil based poly. Just make sure the surface of the wood is smooth to the touch. I would not go any smoother, as the paint needs something physical to adhere to. Poly paints are generally self levelling, so you you don't need an ultra smooth surface on the wood - in fact, it's counter productive.

I'd hang the neck so that it is vertical, and then use a smooth motion, keep about 10" away, and mist the headstock starting from the top, slightly overlap. You should be constantly moving, and stop and shake the can every few second. It should only take you a few seconds total to coat the headstock - use smooth motions, and ensure that the paint remains the same distance from the headstock at all times. You should be moving your hand in a straight line, not in a parabola or arc.

Once you've got a good thin coat, let it dry for an hour. Make sure it's dry to the touch, lightly sand with 220 grit, apply the decal, then recoat as needed until the decal is covered. Let it dry and then sand until you're happy.

In short:

Sand back to bare wood
Test for contaminates
If contaminated, use fish eye eliminator
Coat a light coat, wait one hour lightly sand with 220, coat a light coat again, wait an hour, lightly sand with 220
Apply decal and allow to dry
Apply as many coats as you need (sanding lightly at 220 in between) until you are happy

One last piece of advice - this may not be applicable to this paint, but I have seen this with other rattle can paints - some paints can be sensitive to recoat times - like I mentioned above, you either recoat in 1 hour or you wait the full 24 hours dor it to dry before you recoat. Coating "in between," in like 12 hours, messes with the curing process. Again, I'm not sure if it's applicable with this paint, but I've seen it happen quite a few times with other paint from a can.

Hope this helps!

Thanks. A few questions…

Do I do the water test again after applying alcohol? And if the water still beads, then I need fish eye eliminator? I’m well over my budget on all the work I’ve done on this bass as it is so I’d much rather avoid buying more products. This is a one-off project. I don’t do repair work.

If I choose to brush on distilled water and spray an initial coat of poly right after, would I still need fish eye remover? I’m thinking that might be easier than brushing on the poly.

It’s around 70 degrees here. Do you recommend I warm up the can?

If spraying the headstock only takes a couple seconds, how often am I stopping to shake the can?

You said to sand an hour after applying the coat. Folks yesterday said here that you need to wait longer for the coat to cure. So… which is it? Instructions don’t provide a cure time.

 

[Stagelab]

Oh, and when you sand, make sure you clean thoroughly between coats. I use naptha or glass cleaner, and a tack cloth right before the next coat.

You mean apply naptha or glass cleaner after sanding?

I was gonna stick with using painters tape since I don’t have tack cloth.

I have glass cleaner with and without ammonia. Either one fine? Can I use glass cleaner with ammonia to strip the varnish that’s curing now, instead of sanding it off?

 

[Stagelab]

I might be a little late on this, but as a woodworker using a wipe-on technique offers maximum control of finishing bare wood with poyurethane. Thin coats with a high grit sand in between allows a nice build of layers - I even use the poly WITH sandpaper after the first coat to create a super smooth surface. Finish with a wipe-on only coat or brush on for a gloss finish.

Every tutorial I came across for decal applications said to use a spray for the coats after the decal dries. I have the can. I don’t have brush on poly. Would prefer not to buy more products at this stage.

 

[Stagelab]

You should do the water test right before you paint - if it beads, then yes, you need the fish eye eliminator. What's happening is that if the water beads, that indicates that there is some sort of contaminate that has worked it's way into the wood. Whether it's oil, grease silicon, etc., it's seeped into the wood. You're essentially trying to apply a water based paint over oil/silicon, and oil and water won't mix (and silicon prevents the paint from sticking). If the water beads, paint is not going to stick, and that's just physics. The fish eye eliminator takes care of that. You don't need a lot, so if you find that you do need it, I'd search for a small bottle somewhere.



yes, if the water beads. If the water beads then you need the fish eye eliminator - at least that is the easiest and best solution for you. Some of the fish eye eliminator is spray on, some you mix in with the paint (this is what I do, but I use an actual HVLP system). In your case, spraying the water based poly in a cup and adding a drop or two (or however much is recommended) of fish eye remover will getcha where you need to be for the least amount of money.

It's not really needed at that temp, but it wouldn't hurt. I wouldn't stress about this step, but if you find that the paint is going on too thickly then warm it up. Most of the time warming is for larger job - you're not doing a bug area here, so warming it won't make too much of a difference. It it was me, I wouldn't worry about it.



Hang the neck so that the headstock is facing you (you *did* either remove the neck or completely cover and tape up the rest of the bass, didn't you? A well taped up plastic bag is fine to cover the bass if you didn't remove the neck, but I would advise to remove it), if you are right handed, start from the left of the headstock. From 10 inches away, start spraying a little to the left of the headstock and then in a smooth motion and straight line, spray the headstock once going from left to right and then back again going right to left. Total spray time should be about 2 seconds, and you should have a light coat on the top 1/3-ish of the headstock.

Make sure you keep moving constantly and smoothly and that the paint nozzle is at the exact same distance from the headstock the entire time.

Stop. inspect for runs and bubbles. If you see any runs/bubbles, stop, wipe the paint off, then start again. If it's fish-eyeing, then you need to prepare the wood properly.

If no runs/bubbles, shake the cans, and repeat, this time paint the middle of the headstock using the same process - two passes, one from left to right, the other from right to left.

You now have the top 2/3rd's with a single coat.

Stop, inspect, shake, repeat for the bottom. 1/3 of the headstock. Total spray time should be about 1 second per pass, you're making six passes for the initial layer, for a total time of

Stop. Inspect. Repeat the above process.

you now have two light layers of clear coat. this is your base coat. Wait for it to dry for one hour. Sand lightly at 220 grit. Apply decal, repeat the above process once the decal is set and dried.



You don't need to wait for a full cure to sand. An hour for this product is fine if sprayed on, two hours for brush/wipe on - assuming you are not applying it too heavily, the temp is around 70%, and humidity is relatively normal (50%-ish). You are safe to sand - and again, the point is that you are sanding lightly - when the paint doesn't gum up on the sand paper and the clear coat is a fine white powder.

Again, I'll point out that every single guitar/bass manufacturer out there does not take multiple days to do a headstock. You do not need to wait for a full cure to sand.

Thanks for all these details.

I’ll give this a go tomorrow but two things first.

1) rather than sand back to bare wood, could I wipe glass cleaner with ammonia to strip the varnish off? Or a combo of both?

Edit: if ammonia strips varnish, won’t applying glass cleaner with ammonia after sanding remove additional varnish, potentially exposing bare wood?

2) I took the neck off before doing the work and taped up the entire neck besides the face of the headstock. I held the can upright in my right hand and held the neck with my left. Not easy to do, not an ideal setup. I don’t have a work area and am spraying outdoors for safety. No way to hold the neck up on its own. If I stop to shake the can, I’m sure the neck will move a fair amount in my other hand, for what it’s worth. If you have any suggestions, let me know. Very DIY here.

 

[Stagelab]

No. Glass cleaner won't strip varnish off, class cleaner is to ensure that the surface is free of dust, oil, grime, etc. It's a cleaner, it won't remove varnish, either wet or (especially) dried. Take it back to bare wood, do the water test. The water test only works on bare wood - there is no point on doing it on any other surface other than care wood - you are testing for wood contaminates.

You need to removed the paint that is messed up, not sand it smooth. Even if you could sand smooth it so that it looks great (doubtful) the integrity of the paint is compromised. It will flake or get cloudy, or bubble, etc. down the road if it isn't doing it today, and there is a good chance that your decal won't stick.

Again, take it to bare wood. Start from a fully and properly prepared surface. If you search for painting instructions from reputable/knowledgable people, you will hear this time and time again. Proper preparation, technique, and patience. All three are the key.


Dude. You probably should have mentioned this first ...

I'm trying to help, so take this for what it's worth - this is a horrible, terrible idea, and could also be the cause of some of your problems. I can almost guarantee that you are moving the headstock when you paint, which defeats the whole purpose of painting using a straight motion. Keep the gun at right angles to the spraying surface and spray in smooth strokes in order to apply an even coat of material. Always. You are not keeping it at a right angle at all times, and this is contributing to your issues.

Find a way to prop that neck up. It doesn't have to be sticking straight up or down, or hanging. Get an old table and prop it up horizontally. Screw a paint stick into the screw holes on the neck and shove it in to the dirt, or maybe use a few bricks to pop it up. You should be able to figure something out to keep it still while you are painting.

You can put the neck somewhere else while it dries, but you have to find a way to keep it motionless while painting, else you will continue to have issues.

Also, now I have to mention this as well - you need eye protection and at least a paint mask, if not a respirator. You don't want to breathe that poopie in and you definitely don't want it in your eyes. You're doing this outside? All it takes is a gust of wind at the wrong time and you will have a lot more issues than some bubbly paint.

My local hardware store has basic safety glasses for $.99, good ones for less than $2.00. I use a respirator, but paint masks are a buck or two for a pack of three. This is by far the most important advice that I can give you. Don't mess around with this.

I have safety glasses. I used a KN95 before.

There’s an old desk outside my building. Might be able to rest the headstock against it. I’ll see what I can figure out.

For some reason I was told a while ago that ammonia could be used to strip varnish. I even bought the glass cleaner with ammonia for that reason. Never ended up using it.

You mentioned a spray gun. I don’t own one. I’m spraying from the can.

 

[Stagelab]

KN95 masks don't filter out the gasses from paint - it's not doing any good, and in fact might even be worse than no mask at all. Seriously, don't cheap out on your safety, these things are nothing to mess around with. Get at least a cheap paint mask. If you listen to anything that I have to say, it should be that

Ammonia can be used as a paint stripper, but not in the concentrations in glass cleaner, especially not for poly finishes after they have dried. You would need a very strong concentration (glass cleaner is about 5% ammonia - you'd be looking at 33% ammonia at a minimum for paint stripper, plus other chemicals). In addition, you should never use ammonia based paint strippers on wood as they will damage the wood.

Spray gun/can, same principle.

Mine’s an N95, actually. The disposable kind. Is that what you were referring to? The legit painters masks are a bit more than I want to spend.

Makes sense. If glass cleaner stripped varnish, there’d be a lot more damaged tables in the world.

 

[Stagelab]

No, a N95 isn't going to be any different. That being said, I kinda forgot that you're just doing a small section for a couple seconds. Just don't breathe in while you're spraying and with the small amount that you're doing you should be fine.

Sanded back to bare wood. Distilled water absorbed into the wood within 90 seconds so no need for fish eye eliminator. Pic attached. I found a trash can heavy enough to hold the neck. Neck is leaning back quite a bit. Can still spray with the can upright. Good enough?

 

[Stagelab]

The trash can is just like something I would use just make sure you're hitting it at a right angle, light misting coats like described above. Don't get impatient, and remember, when you go to sand, if the paper gets gummy OR if you don't get fine white powder, it still needs to dry

Good luck!

Thanks. One thing: you recommended lightly sanding with 220 after the decal dries. Isn’t such a low grit a risk for sanding into the decal and ruining it? Videos I watched show people wet sanding with 800 or 1000 after the decal is applied. Edit: I think those people were using oil based varnishes for the most part. I’m fine dry sanding with 220 BEFORE the decal is applied.

 

[Stagelab]

Don't sand with 220 after you apply the decal. If I said that, I was wrong, I was most likely not thinking about the decal, just the overall process. The videos are correct, a light sand with 800/1000 is much better.

So yes - 220 before the decal is applied, not after.

Edit: I see what I did above and corrected it. What I meant was to repeat the process with spraying the clear coat, not the sanding. The hazards of typing on my phone. Glad you caught it, 220 on the decal would have messed it up for sure.

I applied DNA, let it dry, then brushed on the poly which I warmed up first and thinned with distilled water. No orange peel. Waited an hour then sanded. Brushed on another coat for good measure. No orange peel. Waited an hour then sanded. Sprayed a mist coat — 10” away, zig zag, no more than 1/2 second per zig or zag, shook can every couple passes. Result: orange peel. Pic attached. There’s orange peel throughout the headstock. Easy to see where the light shines on the wood.

I don’t know what if anything is going wrong. At this stage I’m planning to sand with 220 after this coat dries, and then apply the decal.

 

[Reedt2000]

I applied DNA, let it dry, then brushed on the poly which I warmed up first and thinned with distilled water. No orange peel. Waited an hour. Brushed on another coat for good measure. No orange peel. Waited an hour. Sprayed a mist coat — 10” away, zig zag, no more than 1/2 second per zig or zag, shook can every couple passes. Result: orange peel. Pic attached. There’s orange peel throughout the headstock. Easy to see where the light shines on the wood.

I don’t know what if anything is going wrong. At this stage I’m planning to sand with 220 after this coat dries, and then apply the decal.

Crap, if brushing was working for you, just keep doing it that way. You can still wet sand it once the build up is what you want. Some orange peel is expected when you spray, but that looks too pronounced to be the typical texture you get from a rattle can...

 

[Stagelab]

Dude ...

You only need a light coat, and you're mixing application methods. Brushing on and misting on are not the same thing - you'll get a heavier coat with brushing on, especially with the second coat.

Your second brushed on coat was not fully dry, and you didn't sand between coats. I've explained this to you, I literally posted this yesterday -

"You don't need to wait for a full cure to sand. An hour for this product is fine if sprayed on, two hours for brush/wipe on - assuming you are not applying it too heavily, the temp is around 70%, and humidity is relatively normal (50%-ish). You are safe to sand - and again, the point is that you are sanding lightly - when the paint doesn't gum up on the sand paper and the clear coat is a fine white powder."

2 hours after brush on to dry.

You need to 1) be patient 2) follow the directions. That's it.

I honestly don't know why you would brush on two coats and then spray another coat, while not lightly sanding in between coats or checking if the coats are dry - or at least waiting 2 hours for the brush on coat to dry, per the instructions that I provided. Also, after two coats, a third coat is totally unnecessary.

I don't know what else to say.

I gently sanded in between coats. And my brush on layer was so extremely thin (probably added more distilled water than necessary) which is why I doubled it. The decal maker told me the headstock needs to have a shiny surface first so the decal adheres. After the two brush on coats the surface was not shiny at all. Edit: this begs the question, if I lightly sand with 220 will it remove all the shine?

I actually contacted the maker of the poly this AM and explained how I was trying to brush it on. The customer service rep told me an hour dry time before adding any subsequent coats since I’m using the poly from the spray can and not the brush on product. It was a surprise to me.

I’ll give it another shot waiting 2 hrs after brush on. I’ll sand then spray a second layer and see how it looks.

Edit: if I remember right, you haven’t worked with water based poly spray. Is that right? Maybe some of this peel has to do with the product itself.

 

[Stagelab]

Crap, if brushing was working for you, just keep doing it that way. You can still wet sand it once the build up is what you want. Some orange peel is expected when you spray, but that looks too pronounced to be the typical texture you get from a rattle can...

I’d brush on every layer but all the decal videos and the decal maker said to use spray. I wonder what the risk is to brushing it on top of the dried decal.

 

[Reedt2000]

I’d brush on every layer but all the decal videos and the decal maker said to use spray. I wonder what the risk is to brushing it on top of the dried decal.

Decal is probally super thin, and activated by liquid. I could see the product loosening it, and the brush sliding it around. I wonder if you could pour it on and let it self level. Would have to clamp the neck so the face was perfectly level