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  #1  
Old 05-04-2021, 02:01 PM
stefanj stefanj is offline
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Default Paint Mystery!

OK. Interesting paint mystery.

I just put a couple of coats of pricey automotive lacquer on my Estes PS2 "Sahara."

It fogged up a bit, which is something that happens in high humidity and not alarming. Drying in a hot place, or buffing, gets rid of the haze. I'm planning on polishing and buffing before the clear coat goes on anyway.

But look at the stripes in the haze on my Sahara. . . . pictures 1 and 2. Shiny, haze-free stripes, around the tube in two places, and leading forward from the fin.

What's happening there?

I know why what's happening is happening *there*, but not *why.*

The ring-shaped spots are where the plywood centering rings are that support the interior motor mount tube. The stripe leading up the tube is on the other side of the basswood strip you see inside, as seen in photo #3.

It is a long known "thing" that some adhesives shrink a bit as the dry or cure. This can cause a very, very slight drawing in and flattening of the body tube over an interior piece.

But given that, why is the haze avoiding those spots?
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  #2  
Old 05-04-2021, 02:13 PM
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SEL SEL is offline
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Quote:
Originally Posted by stefanj
OK. Interesting paint mystery.

I just put a couple of coats of pricey automotive lacquer on my Estes PS2 "Sahara."

It fogged up a bit, which is something that happens in high humidity and not alarming. Drying in a hot place, or buffing, gets rid of the haze. I'm planning on polishing and buffing before the clear coat goes on anyway.

But look at the stripes in the haze on my Sahara. . . . pictures 1 and 2. Shiny, haze-free stripes, around the tube in two places, and leading forward from the fin.

What's happening there?

I know why what's happening is happening *there*, but not *why.*

The ring-shaped spots are where the plywood centering rings are that support the interior motor mount tube. The stripe leading up the tube is on the other side of the basswood strip you see inside, as seen in photo #3.

It is a long known "thing" that some adhesives shrink a bit as the dry or cure. This can cause a very, very slight drawing in and flattening of the body tube over an interior piece.

But given that, why is the haze avoiding those spots?


Just a guess, but could it be that the adhesive you used is seeping through the tube
Just Enough to cause the glossy sheen?
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Old 05-04-2021, 02:21 PM
stefanj stefanj is offline
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Quote:
Originally Posted by SEL
Just a guess, but could it be that the adhesive you used is seeping through the tube
Just Enough to cause the glossy sheen?


Some background:

Model was built in late 2018.

Primed (Kilz) 2019.

Primer sanded off last month. More primer went on, and mostly sanded off.

Two or three coats of white paint. Waited a week. Another coat or two of white.

Wet sanded and compounded (polishing compound).

So, little chance of any adhesive working its way through!

Something *mechanical" is happening.
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Old 05-04-2021, 02:22 PM
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Earl Earl is offline
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The fogged areas are where places on the tube got colder from the sprayed paint and allowed moisture to condense from the air and form on the surface of the paint.

My guess is that more than likely, the areas where the glue is are denser. Therefore, it took 'more' cooling to get them cold enough to condense moisture. In your case, those areas did not get quite cold enough to condense enough moisture to fog the paint.

I stuff the inside of my body tubes with paper towels or whatever to 'insulate' them somewhat. Even though it is on the inside, it helps prevent the tube from getting so cold as to condense moisture out of the air. Well, at least it helps. And here in the south, we need all the help we can get to fight moisture and humidity. It REALLY affects spray painting big time.

Earl
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Old 05-04-2021, 02:38 PM
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tbzep tbzep is offline
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Quote:
Originally Posted by Earl
The fogged areas are where places on the tube got colder from the sprayed paint and allowed moisture to condense from the air and form on the surface of the paint.

My guess is that more than likely, the areas where the glue is are denser. Therefore, it took 'more' cooling to get them cold enough to condense moisture. In your case, those areas did not get quite cold enough to condense enough moisture to fog the paint.

I stuff the inside of my body tubes with paper towels or whatever to 'insulate' them somewhat. Even though it is on the inside, it helps prevent the tube from getting so cold as to condense moisture out of the air. Well, at least it helps. And here in the south, we need all the help we can get to fight moisture and humidity. It REALLY affects spray painting big time.

Earl

I think we have a winner.
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  #6  
Old 05-04-2021, 02:45 PM
stefanj stefanj is offline
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Interesting! That sounds reasonable.

It is getting sunny. I think I will relocate the parts up to my balcony.
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  #7  
Old 05-04-2021, 02:55 PM
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SEL SEL is offline
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Quote:
Originally Posted by stefanj
Some background:

Model was built in late 2018.

Primed (Kilz) 2019.

Primer sanded off last month. More primer went on, and mostly sanded off.

Two or three coats of white paint. Waited a week. Another coat or two of white.

Wet sanded and compounded (polishing compound).

So, little chance of any adhesive working its way through!

Something *mechanical" is happening.


Oh. The only other explanation, then, is FM.
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  #8  
Old 05-04-2021, 02:57 PM
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Earl Earl is offline
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Quote:
Originally Posted by TigerHawk
Earl,

Does this happen if an airbrush is used or is it just rattle can spray painting?


If one were using a compressor, I would think not. If one were using a 'can' of propellant to drive the airbrush, then yes, I think it would.

It is the propellant in the rattle can (as it goes from liquid to gas the temp drops a great deal) that is what makes the mist of spray paint so cold and accordingly, makes the surface it lands on cold. The surface then becomes like a cold drink in a glass: moisture from the air starts to condense on it.

Earl
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  #9  
Old 05-04-2021, 07:21 PM
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ghrocketman ghrocketman is offline
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+1 to what Earl just said above. Temperature variations causing dis-similar drying.
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  #10  
Old 05-04-2021, 09:37 PM
stefanj stefanj is offline
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A day in the sun got rid of the haze.

While I'm here:

Duplicolor metallic flake paint.

Any problems with wet sanding it (8000 grit)? Polishing compound?

I was hoping to really gloss it up before putting on clear coat.

(Then Stickershock decals! Then more clearcoat! Then automotive wax! I'll be lucky if I can hold this in my hands when I'm done polishing it.)
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