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TrueBlue

What cause paints to do this...

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I've just painted a body with metallic red, no problems. Then began backing it with silver, as I often do. But then the paint was starting to.. whatever it's doing in the attached photo. It's like the paint was spurting out of the nozzle, even though it was spraying perfectly smoothly. it also looks like there might have been a ton of dirt/dust on the body. Also no, it was clean and clear when I started.

The last time I backed in silver was when I painted my Escort Cosworth Monte Carlo and that sprayed on perfectly, so I've no idea why the silver paint decided to go all lumpy like that. I also managed to scratch the silver paint with my nail as even after 30 minutes, in decent heat, it wasn't dry. I might have just layered it too thick in that area though.

Does anyone know why the paint did/does this? More specifically, what can I do to prevent is happening again? My spray paint method has always been the same and I've never encountered an issue like this before. My fault or the paint? Do let me know!!

IMG_20200915_163139_1.jpg

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It is hard to tell from the pictures but I have had the same looking effect using my AB and the paint drying before it hits the surface. Was it hot or was you at more distance or as said was can getting low?

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BUSDRIVER: From the outside it looks fine. Can't seen anything wrong when viewed from the outside. Thankfully, it started after a few coats, otherwise if it happened on the first coat, you might have been able to see it from the outside. And no, the can was at least half full at that point. 

BGAZZALENE: It's fairly warm, for the the UK at least, but wasn't hot enough to dry the paint almost right after leaving the can. I was quite close to the inside of the body, probably about 10cm or so (might have been too close), and as mention above, the can was pretty much still half full.

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I've had cans sputter like that when I neglected to clean the nozzle after the last use. Do you clean it out by spraying upside-down until paint stops coming out? If not, the nozzle might be clogged up. Sometimes you can soak them in paint thinner to clear it up.

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As above it looks like dry spray where the paint has lost liquidity before hitting the surface. Does the rough coat flake off? If so, yeah, probably dry spray. 

 

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MARKBT73: Hm, to be honest, not always. If I'm even more honest, I've very rarely HAD to clean the nozzle. Every can of Tamiya paint I've ever used has always sprayed smoothly and evenly, right down to the last bit. This is the first time the paint has gone a bit flaky up on me.

HOWARDS: I tried to brush it off, but the flakes didn't budge. They're moulded into the paint , and they're not simply loose on the surface or anything. 

I've actually stuck the shell on eBay, as things just went further downhill from there. Which is a shame, since I got the body and paint only today. I've listed it for bashing, since it didn't come out looking very good. Oh well, hope to claw back some money from the sale, get another body, back it with WHITE this time, as I no longer trust silver, lol.

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Not shaking the can enough before spraying OR the air temp being too cold or hot OR the humidity being too high OR trying to squeeze the last few drops from the can before it is empty?

I have suffered same, even on my 1:1 Land Rover when spraying in sub-optimal conditions. I would guess not shaking the can long enough and the paint being too cold is primary cause. I tend to shake cans for a good 5 minutes now before spraying, always spray on a test piece before using on actual car and make sure paint is warmed first. UK is not the best environment for spraying because 99.99% of the year it is too cold, too warm or too humid to paint..... ;-) ;-)

 

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22 minutes ago, TrueBlue said:

as things just went further downhill from there

What else went wrong?

Tamiya silver is quite dark, if it was Tamiya silver. The Bright Silver is much more fun. Can get some lovely subtle metallics with it. 

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1 hour ago, Howards said:

As above it looks like dry spray where the paint has lost liquidity before hitting the surface. Does the rough coat flake off? If so, yeah, probably dry spray. 

 

My thoughts exactly.

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Yeah, definitely beginning to wish I'd gone with Bright Silver, but the website I bought all the paints and body shell from was out of stock of Bright Silver, so I went for the next in line... normal Tamiya silver.

What else went wrong? Well, after the unfortunate mess of the silver paint, I applied the decals. The front window decal has multiple creases in it where I was (trying to) carefully apply it to the body. One window sticker ended up with little lumps under it, even though I'm sure it was free of dirt and dust. And the other side window has a large crease in it because I didn't lay the sticker flat and even. And one of the Rustler 4x4 decals tore when i tried to remove it from the sheet.

Other than that... all peachy, lol.

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1 hour ago, TrueBlue said:

Yeah, definitely beginning to wish I'd gone with Bright Silver, but the website I bought all the paints and body shell from was out of stock of Bright Silver, so I went for the next in line... normal Tamiya silver.

What else went wrong? Well, after the unfortunate mess of the silver paint, I applied the decals. The front window decal has multiple creases in it where I was (trying to) carefully apply it to the body. One window sticker ended up with little lumps under it, even though I'm sure it was free of dirt and dust. And the other side window has a large crease in it because I didn't lay the sticker flat and even. And one of the Rustler 4x4 decals tore when i tried to remove it from the sheet.

Other than that... all peachy, lol.

Regarding stickering, try spraying the body with very dilute washing-up liquid solution on the area the sticker is to be applied (or simply dip the sticker in a small bath of the solution). The sticker floats on the layer of soap solution so you can position it while avoiding creases. Then once you're happy with the position, squeeze out the soap solution from the middle outwards. 

I did this on the last body I did, after only ever applying then dry, and it was so much easier to get good results. Applying heat using a hair drier also helps with creases on curved areas. 

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RICH_F: I've been meaning to try that method a few times, but I'm always paranoid that the water/soap combination will completely remove the adhesive on the stickers... even though I've seen YouTube videos of people doing it so I know it doesn't, but I still think it will... I'll probably give it a shot. Can't make it any worse than it already is!

Will it work OK for stickers that have already been applied, or will it not have any effect on the adhesive?

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My guess is a droplet forming at the bottom of the nozzle.  

Which is essentially what @markbt73 already said.  

txEGPow.jpg

At the bottom of the nozzle sometimes a large droplet develops.  When the compressed air blows on it, it makes smaller droplets.  Think of little pool of water on the lip of an unopened beer can.  If you blow on it, it will splatter all over.  That's what could be happening.   

ZyamnLr.jpg

There are 2 things you could do. 

1) Clean the nozzle after every spray.  If the nozzle has a droplet hanging, I fling it away.  If it doesn't fling away, I use a piece of a paper towel to dab it away.  Then spray upside down for half a second.  That keeps the nozzle clear for the next spray. (even if next spray is in 15 minutes)  If you don't do this, the one large droplet at the chin of the nozzle will solidify, and provide a platform for more droplets next time.  

2) Spray from about 30cm away and vertically. Even if some droplets form they fall to the ground.  

62dXN3P.jpg

(of course above is not to scale, because that'd be one gigantic spray can)  

P.S.  If you want, you could use @ before a member's name, that will highlight their IDs and they'll be notified.   

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I think it's dry overspray.  This video discusses the issue and yes, it's for paint guns, but the problem still applies to paint applied via spray cans as well.  It's just that with a spray can you can't control the mixture ratio, nozzle size or type of propellant.  But you do have other controls.

https://www.youtube.com/watch?v=h9TlMmTVBPU

My guess is the combination of weather including the high temperature and relatively low humidity combined with the distance away from spraying, the angle of spray and the inside body shape all conspired to create specific air currents that resulted in dry overspray falling on the inside of the body and causing a "sandpaper surface".  It could also have been related to the pressure inside the paint can and the mixture ratio of paint to propellant, but this is less likely given Tamiya's good quality control standards, though temperature does have an effect on this.

To combat this problem, I would try to change the angle of the body so it's more vertical so the overspray misses the inside of the body and lands on the floor in front.  Also, maybe move in a little closer when spraying, but speed up the sweeping rate so the same amount of paint is put on the surface per sweep.  Keep an eye on buildup to avoid runs and too-thick coats.

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@Juggular 1. To this day, I've never had to clean the nozzle on a can of spray paint... always a first time for everything. I do sometimes give a quick spray after each coat to help clear the nozzle, but I've never done it upside down. Except once.

2. I do spray with the body vertical nowadays. I used to have it laying upside down in a box, but now I hold it so I can angle the body the way I need to. The distance however, yeah this time \round I was actually quite close to the body, probably too close. I would guess about 10-15cm away.

(If it was to scale, you'd coat the entire body with a single spray!)

P.S. Duly noted!

@Champ85 Very well could be. The UK saw a rise in temperature over the last day or so. But even when we were in the high 20s (high for us anyway) I've never encountered this before. And it happened over the entire body, not a single area is smooth. As mentioned in the above paragraph, I do now paint my bodies by holding them vertically, instead of laying them flat in a box. Makes it much easier. As for distance, I thought I was too close to the body, about 10-15cm... I don't usually go in that close.  But the sweeping rate could have been a bit faster though. I was moving a little slower than usual.

I also think I applied each coat too thick, too soon. I sprayed like 3 coats worth in one go, then let it dry, then did another coat. Possibly, I should have tried to be more patient and just lay down a nice, thin coat each time. I have ordered another body and paint from Wheelspin Models, this time I'm using white to back the metallic red instead. Never backed with white, so... fingers crossed, two times the charm.

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12 minutes ago, TrueBlue said:

I also think I applied each coat too thick, too soon. I sprayed like 3 coats worth in one go

Heh, yeah, don't do this. 

1. Do an initial 'dust coat' - a fine spray from 25-30 cm away moving quickly over the body. This provides something for the next coats to adhere to and helps prevent runs. You don't have to worry about this coat landing dry - Tamiya PS paint is pretty savage stuff and is well sticky. But it should be 'dust' and not 'blobs'. 

2. Do a complete coverage coat again from a fair distance. Move slower over the body to give it a bit more paint. but you are looking to simply get a bit of paint everywhere. Not too thick. 

3. Initial wet coat. Here you are aiming to get enough paint down so that the body looks 'wet'. You can get close. As close as 5-10cm. But the risk here is that too much goes down and it runs. You need to know where to stop and move the can fast do not linger for a moment!. After the initial wet coat, the inside of the body should be smooth and shiny.

4. You can now either apply a backing for effect or tune the tone of the paint by adding more wet coats. 

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17 hours ago, TrueBlue said:

Will it work OK for stickers that have already been applied, or will it not have any effect on the adhesive?

You mean for stickers that are already stuck to the body? No - this won't have any effect as the soap solution needs so come between the body and the adhesive. 

Even if there is a gap and it partiall wicks under, if most of the sticker is stuck down, it won't get under it and enable it to slide. 

For this method to work, the soap solution needs to coat the entire sticky surface of the sticker before it touches the body. Then when you apply pressure to stick the sticker down, and squeegee the solution out, the adhesive comes into contact with the body and becomes permanently stuck (well, as permanent as stickers can be, at least).

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Was it tamiya paint you used to back the body? I have had the same issue with Core rc paints where the nozzle requires regular cleaning IE after every coat or you get the same flakes and lumpiness but, touch wood, never had the same problem with Tamiya

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@rich_f Yep, found out that out when I tried it... thought I'd give it a go, but failed miserably. 

@Wetman It was Tamiya paint, I never use anything else. Tamiya spray paints have always been clean and msooth. Was thinking of using Core RC... bigger cans, smaller price. But have heard some people have issues with the overall colour.  

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Well, my second attempt went much better. Laid down a thin dusting first before adding each additional coat. Let the paint dry for longer. Didn't add 3 coats worth in one go. Used the soapy water method to apply the decals... it didn't make the decals slide, but did make it easier to remove them if needed. All was going well... until I wanted to do something different and added a white stripe on the front. Big mistake. Couldn't get the masking tape to stay in all the grooves, so much red paint bled through. Removed what I could, but some red was left over because I couldn't see it. After I sprayed the white, it became much clearer.

Either way.. this shell is on eBay now too, lol. Not kidding either. Not happy with how either body went. Shouldn't have added that stripe, as it would have been 100% perfect for me to use, but small imperfections like that bum me out. Uh... anyone in the UK looking for a Traxxas Rustler 4x4 VXL body??

Please tho?

Traxxas Rustler 4x4 Body #2 (1).jpg

Traxxas Rustler 4x4 Body #2 (2).jpg

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