Zero paints - gritty finish question

[Mcpesq817]

I tried painting a couple of Gunze Triumph bodies last night with Zero paints, and had a bit of an issue with the paint job being very gritty.  Was worse the first time around, and a little better the second though I did get a bit of grit in some spots.  Any ideas as to what I was doing wrong?  'm guessing the issue was from spraying too heavy of a coat, which I was a little more conscious of on the second body -- on the second, I had a little bit of that issue on the hood and trunk, where i did a couple of passes with the airbrush on the same coat, but not on the sides where the paint job ended up smooth.  I saw a Youtube video of someone spraying that seemed to be spraying a lot heavier coats than I was, so I'm a little bit confused as to why I got the results I did.  I know the finish is supposed to be matte with maybe some bumps, but my paint jobs seemed to be a little excessive on the grit side.  I've got the first body soaking in a Purple Power bath to start over

I was spraying with an Iwata Eclipse 0.35mm at about 20-25psi from about 6-8" away.  Otherwise, the car was primed and lightly sanded glass smooth, rinsed, and hit with tack cloth before spraying the Zero Paints.  All per the Zero Paint instructions, so I don't think it was the prep.

I'm still fairly new to airbrushing and car models in general, but haven't experienced this kind of issue using Vallejo, Tamiya, or Mr. Color.  I haven't done many cars (usually I model planes and ships), but the two car builds I did using Tamiya went down fairly well without issue. I just read the "Matt's tips for painting cars" on Britmodeller -- great tutorial!!  https://www.britmodeller.com/forums/index.php?/topic/234956647-matts-tips-for-painting-cars/  Unfortunately, I can't pinpoint what the issue is here.  

Many thanks in advance!

Edit - here's a picture.  You can see the grit areas on the hood versus the smoother paint job on the left headlight area.

 

Edited January 19, 2021 by Mcpesq817

[Bainford]

I have no experience with Zero, Splash, Gravity, MCW, etc paints, so can't offer specific advice on application. However, the photo seems to show crazing of the plastic. This seems especially visible on the area forward of the bonnet. This occurs when the solvents in the paint physically attack the plastic. Some paint solvents are particularly 'hot', especially lacquers not specifically formulated for styrene plastic (though I have no idea if Zero is lacquer). Additionally, some plastic formulations are particularly susceptible to this reaction. It will be interesting to see if the body soaking in Purple Power shows a grainy surface once the paint has been stripped. You may have to do some priming & sanding with a filler/primer to sort the damage to the plastic.

To prevent this, a barrier is needed between the paint and plastic. A number of products have been used to do this. Most builders ensure a good primer base, and apply the paint in light coats to reduce its potential to attack the plastic. I have heard of BIN and Future being used as barriers, but have no experience with them myself.

Edited January 19, 2021 by Bainford

[Mcpesq817]

Hi Trevor, many thanks for this.  I certainly hope it's not crazing of the plastic, as that might be a nightmare to fix.  I primed the bodies with Mr. Surfacer 1200 which I thought would have been sufficient, but maybe not.  Ugh!  

What's interesting is the FAQs suggest that any primer is ok.  I didn't thin the paint either, so maybe it's not crazing of the plastic?  From the Zero Paints FAQ:

Do they need thinning?
No, all paints are supplied pre-thinned for Airbrush use, they are thinned to a consistency which is suitable for Airbrushes with nozzle sizes of 0.3mm upwards. Additional thinners are available if further thinning is required.
It is not recommended to over thin the paint, too much thinners and increase the chance of the paint becoming to HOT and affecting/eating the plastic below the primer. If unsure test first.

Is Primer needed?
YES, As the paints are solvent based it is necessary to primer the plastic/resin before applying the basecoat colour; this seals the plastic/resin and creates a key for the paint to adhere to. Any brand of primer should be OK, but if in doubt do a test first.

 

Edited January 19, 2021 by Mcpesq817

[Bainford]

I certainly could be wrong about the crazing. It can be hard to tell from a photo, but the area between the head light pods appears that way. Certainly, the wording you posted from the FAQs suggests the paint is indeed hot enough to potentially craze. And as mentioned earlier, the paint is only one component to crazing, the other is the plastic. Like paint, plastic has many different formulations, some of them more prone to crazing then others.

I'm hoping you find it to be a different problem. Striping the paint should tell.

[gman]

Mr Surfacer primer (and the Tamiya I use) are lacquers, but they may not be a sufficient barrier for heavier coats of automotive grade base coats like Zero paints like spraying over an automotive grade lacquer primer would be. 

It does appear you have some crazing- lacquer paints adhere by chemically melting and bonding to previous coats (in this case, your primer). If the base coat is too hot, or is applied too heavily, the solvents will soak into and through your primer coat and reach the plastic substrate to soften and react with that plastic. The solvents may have shocked the plastic, and hopefully once the solvents are fully evaporated, what you see will be the extent of the damage.

I would give the painted model a chance to have all of those solvents fully gas out- it may take a week. A food dehydrator may expedite the process.  Fully sand every surface of the model with fine grit to level it (but don't take it down to primer or bare plastic), and start again. Build up new and extremely light coats of base coat and see if the gritty finish persists, or whether you'll end up with something smooth and even enough for clear coating.

[Mcpesq817]

Ugh, thanks guys, really appreciate it.  I have two bodies that were painted.  One has already been soaking in the Purple Power Bath for the last five or so hours.  I'll probably strip that one completely, since it was the worst by far.  The one in the pictures hasn't gone into the bath, so I'll sand it down and then reapply very light coats.  See whichever approach works best.  

At least these were inexpensive kits.  It's too bad as the colors I was using looked fantastic.  I had a few other colors I ordered for some future models, but now am leery about using them.  Seems like a real pain, especially with the toxicity and clean up and all the rest.

Edited January 19, 2021 by Mcpesq817

[youpey]

Its not everywhere. Is it possible there is too much air pressure and the paint is drying before landing? Or maybe the airbrush is too far back?

[Mcpesq817]

That's what I'm not sure about.  The air pressure was 20-25 which was within the guidelines of the FAQ, and I probably had it around 6" or so away.  

I thought it might be too heavy a coat in some places because as I saw the grittiness, especially on the first body, I went back over it and that just seemed to make it worse.  I'm just not used to this issue with other paints, it's been a bit surprising especially when everyone says how easy these are to use.

[peteski]

7 hours ago, Mcpesq817 said:

That's what I'm not sure about.  The air pressure was 20-25 which was within the guidelines of the FAQ, and I probably had it around 6" or so away.  

I thought it might be too heavy a coat in some places because as I saw the grittiness, especially on the first body, I went back over it and that just seemed to make it worse.  I'm just not used to this issue with other paints, it's been a bit surprising especially when everyone says how easy these are to use.

If you were spraying the paint too heavily, it woudl result in a wet ,shiny (and possibly runny) surface.  Never gritty.
Was the grittiness apparent as you were spraying, or when the paint was wet it was glossy, then the grittiness showed up as the paint dried?

[GeeBee]

Looking at the photo, I'd say you're putting on way too much paint, it looks like it's reacted with the primer coat underneath, basecoats should dry matt but smooth, try lowering the pressure slightly, I don't go above 20 p.s.i when using basecoat. 

[Jhedir6]

I have issues with  Zero Paints doing this sometimes as well. Either you're putting it on way too thick and heavy, causing it to "burn" the primer and creating crazing under the paint and also I'd guess you're getting the grainy texture from the air pressure being too high causing some of the paint to dry in mid air before landing on the body. Turn the pressure down and spray light mist coats and let them dry for 5-10 mins before putting on the next coat. Once you have 5+ light coats on that are dry and no crazing or grittiness then you might try a "wet" coat, but dont go too wet, if there's too much wet paint on the body it will burn through what you have down already.

[Matt Bacon]

You shouldn’t ever have a “wet” coat with Zero base coat paints. Several light coats a few minutes apart should do it. If you spray it too thick, the surface dries before the underneath, which can result in wrinkling, and the remaining solvent eating the primer. It’s a bit hard to tell, but that picture looks to me more like grittiness from the paint drying too soon than crazing the plastic underneath... Glad you found the tutorial helpful, though!

best,

M. 

[Dave G.]

Having not shot Zero specifically but plenty of lacquer, I too shoot base coats at under 20 psi and in closer than 6 inches ( that depends on the thinner used, not sure what Zero uses).Your goal is nice thin even coats, they dry flat anyway so you don't want heavy wet coats that might remain glossy.That's not the goal, you want even but smooth coverage. If I bought some Zero paint I'd do several tests myself before shooting a body with it so I knew what to expect performance wise.

I've shot some lacquers under 15 psi fwiw. So I say experiment with air pressure and distance on a test subject before re-shooting the bodies.

[Mcpesq817]

Thanks guys, really appreciate it.  I couldn't quite figure out if it was from drying too quickly before hitting the body (too much PSI, too far away), or just burning through the primer and crazing the plastic.  The Mr. Surfacer primer is very much like Tamiya primer, so I think I should have been fine there.

11 hours ago, peteski said:

If you were spraying the paint too heavily, it woudl result in a wet ,shiny (and possibly runny) surface.  Never gritty.
Was the grittiness apparent as you were spraying, or when the paint was wet it was glossy, then the grittiness showed up as the paint dried?

When I was spraying the first coat very lightly, I don't recall getting any of that grittiness.  I waited 5 minutes, and then sprayed the second coat.  With the second coat is really when I started noticing it, and I probably made the mistake of going back over it thinking i needed to even the paint out (which I've done with other paints like Tamiya and the Mr. Surfacer/Mr. Color line which self level really well).  So my guess is that I sprayed it on too thick, and probably also had some drying issues.  I've been spraying in a spray booth in my basement, and with the forced air heating, it's very dry in the house which probably doesn't help things.  I'll try spraying closer and at lower PSI and see how that goes.  

I also have a GSI-Creos PS-290 airbrush with I believe a 0.5mm needle.  Would that be better to spray Zero Paints with over the Iwata Eclipse with 0.35mm needle?  It shoots a bigger cone of spray really nicely.  Maybe I should have used that one instead - part of the reason I got it was for larger areas to spray like car bodies.

Here's another question for you guys.  The instructions say to spray coats every 5-10 minutes.  Do you guys have issues with the paint drying in the airbrush waiting that amount of time?  Reason I ask is that there is no way I can wait that long spraying Vallejo, which tends to dry quickly and gum up my airbrush.  I didn't seem to have any issues letting the Zero Paint sit in the cup between coats, but wasn't sure if I should think about swabbing the tip with the airbrush cleaner in between coats.

Edited January 20, 2021 by Mcpesq817

[Dave G.]

Usually with lacquer any tip try is melted away as you go to paint again. But you could keep a Qtip handy and a little lacquer thinner to do a little swab out of the tip if need be. Usually just wetting it with the thinner will do it.. If you're doing mist coats though I bet this isn't even an issue. The sides of the cup shouldn't dry, especially if you use a cap on it. When acrylic dries it dries hard, I use Liquitex retarder in my thinner blend for acrylics and it pretty much stops tip dry. Also with acrylic paints you can force flash dry with a hair dryer or even just straight air from the airbrush that quickens the flash off to a minute or two.

I would think the .35 would be fine but then again I use Badger and Paasche Brushes. I think probably my favorite lacquer tip is my Badger .25, beautiful atomization from that tip. I can cut it back to where I don't even see the mist but it magically collects on the surface or do some broader coverage too. I love that tip been using it for some 45 years now. But I'll cut back the Paasche #3 tip too and get good results. Practice is my biggest suggestion.

[Bainford]

26 minutes ago, Dave G. said:

I think probably my favorite lacquer tip is my Badger .25, beautiful atomization from that tip.

Are you referring to a Badger 200 or 100 with fine tip?

[Dave G.]

14 minutes ago, Bainford said:

Are you referring to a Badger 200 or 100 with fine tip?

In my case 200 but the same tip fits the 100. I use the 200 with side cup. I also use the .5 tip but my main one is the fine. My 200 is the old style with screw in tips. Listen, I'm not saying go out and buy one lol !! You should be able to get a nice finish with what you have.

 

[Bainford]

1 hour ago, Dave G. said:

In my case 200 but the same tip fits the 100. I use the 200 with side cup. I also use the .5 tip but my main one is the fine. My 200 is the old style with screw in tips. Listen, I'm not saying go out and buy one lol !! You should be able to get a nice finish with what you have.

 

Cheers Dave. I have an old style Badger 200, bottom feed, that I have been using for 39 years, that's why I asked. I have a fine head/needle but never used it, the medium set being my main set-up. Actually, last winter I finally bought a long desired gravity feed, dual action airbrush, but was intrigued by your comments above. Thanks.

[Dave G.]

56 minutes ago, Bainford said:

Cheers Dave. I have an old style Badger 200, bottom feed, that I have been using for 39 years, that's why I asked. I have a fine head/needle but never used it, the medium set being my main set-up. Actually, last winter I finally bought a long desired gravity feed, dual action airbrush, but was intrigued by your comments above. Thanks.

 The medium is good too but that .25 is exceptional to me. You probably get the same paint job in the end but to me the .25 is just sweet. Another thing I do is use the fine needle with medium tip, the transition from light to heavy spray is slower. You wouldn't think so but it is.

[peteski]

6 hours ago, Mcpesq817 said:

When I was spraying the first coat very lightly, I don't recall getting any of that grittiness.  I waited 5 minutes, and then sprayed the second coat.  With the second coat is really when I started noticing it, and I probably made the mistake of going back over it thinking i needed to even the paint out (which I've done with other paints like Tamiya and the Mr. Surfacer/Mr. Color line which self level really well).  So my guess is that I sprayed it on too thick, and probably also had some drying issues.  I've been spraying in a spray booth in my basement, and with the forced air heating, it's very dry in the house which probably doesn't help things.  I'll try spraying closer and at lower PSI and see how that goes.  

I guess my airbrushing technique is unconventional. I like to lay down wet (thus shiny) coats.  I don't do the light dusting spraying.  I also never sand or rub out my paint jobs.  But I guess I'm more willing to take risk of paint runs than other modelers.

You say that you sprayed it on too thick.  Probably too thick, and too dry.  If I was painting, I would open up the nozzle to have more paint flow out and go on wet.

I have been using my Badger 200 airbrush with medium nozzle and siphon feed for over 30 years, and I'm used to the way it works.

Edited January 20, 2021 by peteski

[Dave G.]

55 minutes ago, peteski said:

I guess my airbrushing technique is unconventional. I like to lay down wet (thus shiny) coats.  I don't do the light dusting spraying.  I also never sand or rub out my paint jobs.  But I guess I'm more willing to take risk of paint runs than other modelers.

You say that you sprayed it on too thick.  Probably too thick, and too dry.  If I was painting, I would open up the nozzle to have more paint flow out and go on wet.

I have been using my Badger 200 airbrush with medium nozzle and siphon feed for over 30 years, and I'm used to the way it works.

Oh I do wet coats too, just generally not with hot lacquer on plastic. The new hybrid lacquers you can about pour on. Tamiya acrylic goes on nice wet too but that itself is more hybrid lacquer itself. And enamel I always did wet. And actually at that with the .25 it's still a wet coat but thin due to the fine spray with hot lacquer, can't say by any means it's a dry coat..

Edited January 20, 2021 by Dave G.

[peteski]

1 hour ago, Dave G. said:

Oh I do wet coats too, just generally not with hot lacquer on plastic.

. . .

I was referring to MP and his technique, which seemingly resulted in gritty finish.

[Michael jones]

Looks like what happens when you apply too wet and it eats through the primer causing the damage to the plastic. I've never sprayed zero before, but id guess pressure too high (usually only really need 15psi). Also it probably would not have been so harsh with some retarder added. With Tamiya paints using lacquer retarder, you can easily spray directly on plastic with no issues. I have encountered issues like yours when using auto paints a few years ago.

Mike

Looks like what happens when you apply too wet and it eats through the primer causing the damage to the plastic. I've never sprayed zero before, but id guess pressure too high (usually only really need 15psi). Also it probably would not have been so harsh with some retarder added. With Tamiya paints using lacquer retarder, you can easily spray directly on plastic with no issues. I have encountered issues like yours when using auto paints a few years ago.

Mike

[Dave G.]

28 minutes ago, peteski said:

I was referring to MP and his technique, which seemingly resulted in gritty finish.

Sorry, didn't even notice the quote or rather whose it was .

[peteski]

Upon reviewing the photos again I do agree that the problem is not pebbly paint but fine wrinkles (crazing) in the plastic caused by the "hot" solvent in the paint.  Unfortunately those wrinkles will remain even if the paint is stripped.  Not sure what would be a good way to fix this.  Probably a lot of elbow grease.

Edited January 21, 2021 by peteski