paint beading on plastic

Discussion in 'Weathering Forum' started by eric halpin, Aug 8, 2007.

  1. eric halpin

    eric halpin Eric Halpin

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    I am in the process of weathering my recently assembled two stall diesel engine house by Walthers. Using a heavily diluted water based 'grimy black' the walls with brick accents, window sills, etc have weathered nicely. However, this same paint on the roof beads up like crazy! What is different about roof and walls and what do I do about stopping the beads?

    Thanks
    Eric
  2. UP SD40-2

    UP SD40-2 Senior Member

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    Eric, if you have already painted the plastic, my advice wont help:frowns: , but before i do ANYTHING to plastic kits/parts, i ALWAYS wash them off with rubbing alcohol:winki: . what that does is takes off any oils, or mold separating chemicals so the plastic is clean:winki: . doing that, keeps problems like you are having from happening:thumb: . hope this helps:smilie:
    :deano: -Deano

    EDIT: i use 70% isopropyl alcohol for this, NOT the 90%, the 90% strength might remove decals or paint on box cars, etc.:eeki: also, wipe it down quickly, and take it off quickly:winki: .

    EDIT/EDIT: washing the parts with warm water and dish soap would ALSO work:thumb: , AGAIN, do this BEFORE you start the project:winki: . this is the safest way to clean the plastic if you want to leave it EXACTLY as it looks right from the box:winki: .
  3. doctorwayne

    doctorwayne Active Member

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    If you've already done the cleaning as Dean suggested, you could also try adding a drop or two of liquid dish detergent to your paint wash. This reduces the surface tension of the paint, preventing it from beading. I'm told that a little alcohol will also work, but I find the detergent cheaper. Besides, why waste alcohol? The proper alcohol, taken internally, is also good for relieving tension of another sort.;):-D

    Wayne
  4. MasonJar

    MasonJar It's not rocket surgery

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    Eric -

    What's the finish on the roof - is it some sort of texture? Does the plastic seem different than the other parts?

    Washing may help. If the finish is smooth, you can always give it a bit of "tooth" by sanding with 400 grit wet/dry paper (use it wet). But if that would destroy any texture the roof has, it may not be an option.

    The old standby is DullCote. A shot of this may give the plastic enough texture so the paint will behave.

    Last resort is to try a drybrush technique. I have found when all else fails, this will work. It is not appropriate for a super smooth, even finish, but since you are looking for a "weathered roof" look, it may be fine.

    Andrew
  5. eric halpin

    eric halpin Eric Halpin

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    paint beading

    Good info fellas. Next time I shall 'wash' the parts that will be painted or weathered. However, as this kit is now assembled I shall try the alcohol wash first then the dullcote if necessary. The roof does have a type of shingle image so a light sanding, as suggested, is an option.

    Thanks
    Eric
  6. UP SD40-2

    UP SD40-2 Senior Member

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    NOT to step on Andrews dull coat advice:winki: , but i would use cation when painting OVER dull coat with water based paints, MY luck with that has been whatever water based color i put over Dull coat...turns chalky white:eeki::frowns: .
    :deano: -Deano

    EDIT: i use rubbing Alcohol to thin my water based paints...this could have something to do with it:eeki::toug::119: .
  7. doctorwayne

    doctorwayne Active Member

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    I think that you've found the cause right there, Dean. Yet another reason for keeping the alcohol in a glass, with just a little ice. ;) If you thin your water-based paints with distilled water, and add a drop or two of liquid dish detergent, the Dulcote will not be affected at all.

    Wayne
  8. UP SD40-2

    UP SD40-2 Senior Member

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    :oops: ...well, dog gone it Wayne...i quit drinking about 15yrs ago, so i put my alcohol in paint:119: . Seriously though(but i did quit drinking 15yrs ago:winki: ), i use rubbing alcohol to thin water based paint to speed up the drying time, and i feel it leaves a better finish:winki: .
    :deano: -Deano
  9. doctorwayne

    doctorwayne Active Member

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    Hey, no offense intended with the reference to booze.
    I don't use alcohol for thinning paint because I usually use Floquil or other lacquer-based paints. While I did use Polly Scale to paint GERN, that was mainly because it was done in the winter, so I couldn't do the painting outside with Floquil (the building, even in sections, was too large to fit in my spray booth and the fumes would've stunk-up the whole house). I have a separate room for painting, so I just closed the door, turned on the exhaust fan, donned my respirator, and started spraying. The dust problem wasn't too bad, and there was no odour, but that stuff is not a lot of fun to spray and it's a lot harder to clean the airbrush when you're finished. I usually use it only for weathering washes, thinned with water, or, unthinned for painting rails on the layout, in both cases using a brush. Neither of those tasks require a good finish.

    Wayne
  10. UP SD40-2

    UP SD40-2 Senior Member

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    MY GOOD FRIEND Wayne, absolutely NO offense taken:winki::mrgreen: , heck, just because i quit drinking doesn't mean ANYONE else should:thumb: , i just felt it was time for ME to quit:winki::smilie: . (lets NOT talk about my excessive use of cigarettes and coffee though...:oops: )

    though i too use Floquil for SOME projects, living in an apartment building i use Polly Scale paints more often, for the same reason you mentioned..its pretty much odorless:winki: . I'll spray the project outside, then have to bring it in right away to avoid bugs & dirt from getting into it. using alcohol, speeds the paint drying time up, and gives a nice finish, so living where i do, i find its an advantage for me to use it:winki: .
    :deano: -Deano
  11. MasonJar

    MasonJar It's not rocket surgery

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    If you do happen to "craze" the DullCote with alcohol (e.g. India ink in alcohol wash), fortunately, another application of DullCote will fix it right up.

    Andrew
  12. eric halpin

    eric halpin Eric Halpin

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    Just a quick final question on this matter. If I use a lacquer type paint on the roof or any other component for that matter and it is still too shinny, can I then just apply a light coating of Dullcote over the painted surface to tone the shine down?
  13. doctorwayne

    doctorwayne Active Member

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    Dullcote will work over most types of paint, but a lacquer-based paint should be sprayed if you're applying it on plastic, or over a water-based paint. Brushing it on plastic tends to "craze" the surface of the plastic, mainly due to the high concentration of thinner: when sprayed, the thinner evaporates much more quickly, resulting in little or no damage to the plastic. Dullcote itself is lacquer-based. Brushing a lacquer-based paint over a water-based paint may lift or otherwise damage the original finish.

    Wayne
  14. santafewillie

    santafewillie Member

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    Andrew, thanks for the tip about reapplying the Dullcote. I learned a while back not to mix alcohol and Dullcote the hard way. Chalked about a half dozen structures/freightcars before I learned...someone posted the reason on the Gauge.
  15. Dayton

    Dayton New Member

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    I found that sometimes that "chalky" look adds to the realism of the structure. Paint fades in real life, so if done properly, that could be a plus.
  16. Gainer

    Gainer Member

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    about the dish soap, make sure there are no surfactents, thats what gives it that shiny finish, it is a filmy residue sometimes.