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Author Topic: Paint separation issues  (Read 3836 times)

Offline Sean McEntee

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Paint separation issues
« on: May 30, 2017, 02:03:00 PM »
        Painting a model which required some mixing of Brodak Insignia White and Miami Blue to get a bit of a Powder Blue color.  Shook the bajezus out of the can when mixing and sprayed it on and everything looked great when all was said and done.  Went to sand down some areas and what was underneath was considerably darker!  Not a big issue at this point as I plan on shooting a second coat anyway.

        Just curious to see if anyone knows what the deal is.  Is it possibly separating after I spray it?  I made a pretty big batch of this color, and I suppose my concern is that the same batch of paint may not match itself, as weird as that may seem, between coats.

Offline billbyles

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Re: Paint separation issues
« Reply #1 on: May 30, 2017, 02:34:48 PM »
       Painting a model which required some mixing of Brodak Insignia White and Miami Blue to get a bit of a Powder Blue color.  Shook the bajezus out of the can when mixing and sprayed it on and everything looked great when all was said and done.  Went to sand down some areas and what was underneath was considerably darker!  Not a big issue at this point as I plan on shooting a second coat anyway.

        Just curious to see if anyone knows what the deal is.  Is it possibly separating after I spray it?  I made a pretty big batch of this color, and I suppose my concern is that the same batch of paint may not match itself, as weird as that may seem, between coats.

Hi Sean,

Not sure what could cause your problem with the "layered" colors.  I have a couple of questions...did you mix the white & blue in a clean, fresh container or did you mix it by, say, pouring white in the blue container, then thinning the mix & spraying the resulting mix?  If you mixed in the blue container then some of the more concentrated blue in the bottom could figure into the mix when spraying.  Although I am not familiar with Brodak's dope, it is a butyrate dope mixed to John's specs so it should act like any butyrate which is pretty predictable & trouble-free.

Another thought - What kind of spray gun are you using?  How long after you shook the dope mix was it before you put it into the spray gun?  Did you put on just one coat or did you go ahead & put on two coats? There are so many variables that it is difficult for me to put a finger on the problem.  Even if the dope in the gun sat for awhile and some pigment settled out the blue & white would settle at very nearly the same rate.

Bill Byles
AMA 20913
So. Cal.

Offline john e. holliday

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Re: Paint separation issues
« Reply #2 on: May 30, 2017, 02:45:13 PM »
Yep, both colors should have went into an old Mason Canning jar big enough to hold both colors and the thinner that will get the last of the pigment off the bottom of the jars/cans.
John E. "DOC" Holliday
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Offline Sean McEntee

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Re: Paint separation issues
« Reply #3 on: May 30, 2017, 03:05:07 PM »
Bill and Doc,

      Good Questions.  I pour both colors into a cleaned up container, usually an old thinner or clear dope container to reduce color contamination.  I made a good deal more of this mix then I need to make sure I don't run out, and in case I need to make repairs later.  Then I pour it into another clean container and mix with thinner and retarder if needed.  Then it goes right in the gun (Husky LVLP spray gun) and sprayed right on the model.  Little to no lag time so it doesn't sit there long enough to separate.  That's whats weird about this phenomenon to me.  If the paint was separating before spraying, it would vary in shade across the model.  However it is uniform at the surface.  Sanding through it, it gets darker as I sand down into it.  This is the first coat of color dope; nothing but clear underneath it.

      Could humidity (or lack thereof) play a factor?  It was a parching 37% humidity in my garage.  I wasn't using retarder (which was a mistake and why I'm doing some sanding). 


Doc:  I'm on Staff Duty all day/night and been playing catch-up.  How's the hand healing up?  Hope all is well!
« Last Edit: May 30, 2017, 04:31:20 PM by Sean McEntee »

Offline Mark Scarborough

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Re: Paint separation issues
« Reply #4 on: May 30, 2017, 06:17:36 PM »
 What happens is with any color mixed with white, grey, light blue and other pastels,, the white pigment is lighter than the colored pigment, so when you spray it, the heavier dark pigments settle to the substrate, thus leaving a slightly lighter shade on the top. You will also see this happen when you spot touch up pastel colors, the edges will get darker and leave you with a ring around the repair unless you apply it semi dry, which with dope is a bad idea
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Offline Sean McEntee

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Re: Paint separation issues
« Reply #5 on: May 30, 2017, 06:28:47 PM »
Winner winner, chicken dinner!  That makes perfect sense.  No way to prevent that, I assume?

Offline Mark Scarborough

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Re: Paint separation issues
« Reply #6 on: May 30, 2017, 06:50:28 PM »
dont use pastel colors,,
or spray it dryer, but thats risky with dope as to dry it will not adhere, one trick I have used is to spray a nice wet coat od clear on, then as soon as it flashes off,  spray the color over it, the clear gives you the adhesion, and with it being fresh, you can spray the color a bit dryer and it wont take as much wet to bite in
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Offline john e. holliday

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Re: Paint separation issues
« Reply #7 on: May 31, 2017, 10:19:56 AM »
Dan, have the brace off the hand for a week now and plan on going to the field with my trusty Ringmaster and short tanking it to get back in shape.  Amazing how out of shape a person gets when he only has one hand to work with and the people tell me not to push it.

I think our paint experts have answered the question quite well.   
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Offline billbyles

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Re: Paint separation issues
« Reply #8 on: May 31, 2017, 11:53:20 AM »
Bill and Doc,

      Good Questions.  I pour both colors into a cleaned up container, usually an old thinner or clear dope container to reduce color contamination.  I made a good deal more of this mix then I need to make sure I don't run out, and in case I need to make repairs later.  Then I pour it into another clean container and mix with thinner and retarder if needed.  Then it goes right in the gun (Husky LVLP spray gun) and sprayed right on the model.  Little to no lag time so it doesn't sit there long enough to separate.  That's whats weird about this phenomenon to me.  If the paint was separating before spraying, it would vary in shade across the model.  However it is uniform at the surface.  Sanding through it, it gets darker as I sand down into it.  This is the first coat of color dope; nothing but clear underneath it.

      Could humidity (or lack thereof) play a factor?  It was a parching 37% humidity in my garage.  I wasn't using retarder (which was a mistake and why I'm doing some sanding). 


Doc:  I'm on Staff Duty all day/night and been playing catch-up.  How's the hand healing up?  Hope all is well!

Hi Sean,

37% humidity is well within the range for spraying dope as long as the temperature is also within the range of 60 to 90 degrees F.  I spray dope at humidity as low as 20% with no retarder and I use only butyrate dope thinner to thin with as it is quite a bit slower than lacquer thinner.  I will use some retarder when the temperature gets in the range of 82 to 85 degrees F & above.  Certified butyrate thinner is by a small margin the fastest evaporating thinner, followed by Randolph thinner, with Sig thinner being the slowest (just for your reference if you are using dope thinner.)
Bill Byles
AMA 20913
So. Cal.

Offline Sean McEntee

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Re: Paint separation issues
« Reply #9 on: May 31, 2017, 02:10:11 PM »
Hi Sean,

37% humidity is well within the range for spraying dope as long as the temperature is also within the range of 60 to 90 degrees F.  I spray dope at humidity as low as 20% with no retarder and I use only butyrate dope thinner to thin with as it is quite a bit slower than lacquer thinner.  I will use some retarder when the temperature gets in the range of 82 to 85 degrees F & above.  Certified butyrate thinner is by a small margin the fastest evaporating thinner, followed by Randolph thinner, with Sig thinner being the slowest (just for your reference if you are using dope thinner.)

Bill,

      Thanks for the info. My problem might be with humidity combined with high temperature.  Temperature my garage reach is almost 100 during the day. I keep the humidity down with a dehumidifier bit not about to go get an AC unit too haha. I'll add some retarder on this next coat.

Offline Chancey Chorney

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Re: Paint separation issues
« Reply #10 on: June 01, 2017, 05:01:10 PM »
Silly question, even though it had been answered. If you have your paint 'mixed' to your specification, would it be an option to go to a local hardware store and possibly ask them to put it on their shaker for a few minutes? Would that be better than hand mixing/shaking? I know my local hardware store would do it, as I had them shake some paint I had sitting around for a while.

Offline Sean McEntee

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Re: Paint separation issues
« Reply #11 on: June 02, 2017, 06:30:15 AM »
Silly question, even though it had been answered. If you have your paint 'mixed' to your specification, would it be an option to go to a local hardware store and possibly ask them to put it on their shaker for a few minutes? Would that be better than hand mixing/shaking? I know my local hardware store would do it, as I had them shake some paint I had sitting around for a while.

I suppose it wouldn't hurt to try, though its really not about how well its mixed, but the weight/density of the lighter color.  I shot some darker blue a couple days ago, and had white float up to the top through that in some spots! 

Offline Sean McEntee

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Re: Paint separation issues
« Reply #12 on: June 02, 2017, 10:54:34 PM »
An interesting footnote:  after sitting for a couple days, I tipped the can to see if the dark blue settled to the bottom. It didn't. Go figure.

Offline Tim Wescott

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Re: Paint separation issues
« Reply #13 on: June 03, 2017, 06:48:49 AM »
I suppose it wouldn't hurt to try, though its really not about how well its mixed, but the weight/density of the lighter color.  I shot some darker blue a couple days ago, and had white float up to the top through that in some spots! 

Are you sure you're not misdiagnosing blushing?
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Offline billbyles

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Re: Paint separation issues
« Reply #14 on: June 03, 2017, 11:03:16 AM »
Are you sure you're not misdiagnosing blushing?

Good call on that Tim.  I was beginning to think that could be the cause.
Bill Byles
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Offline Dan McEntee

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Re: Paint separation issues
« Reply #15 on: June 03, 2017, 04:24:44 PM »
Are you sure you're not misdiagnosing blushing?


     Nah, that can't be it. Sean doesn't get embarrassed very easily!

    Type at you later,
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Offline john e. holliday

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Re: Paint separation issues
« Reply #16 on: June 03, 2017, 06:54:03 PM »
Except when some one tries to look under his kilts. LL~ LL~
John E. "DOC" Holliday
10421 West 56th Terrace
Shawnee, KANSAS  66203
AMA 23530  Have fun as I have and I am still breaking a record.


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