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Humidity and patience...

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  • Member since
    December 2004
Humidity and patience...
Posted by vfxart on Wednesday, May 24, 2006 9:55 PM
Hello and welcome to odd questions of the week, round 2.
This evening our topic is humidty, and using one's best judgment when it comes to whether or not to spray in warmer and/or most definitely humid conditions.

Not having a de-humidifier or air conditioning in the room that I work in (just a single window in front of my work area), I got to thinking (correctly or incorrectly?) that I don't want to push my luck and have something become tacky instead of dry or such, just because of the heat/moisture combination.

I spray either Tamiya or Vallejo in here, with 90% isopropyl, nothing else (no humectants or such)... and am curious how folks deal with this. I can imagine in some areas that if you don't account for this with an appropriate piece of hardware (i.e. above mentioned de-humidifer) then you can go for a long period without laying any color down, or am I being overly paranoid?

My plan for this evening is not to paint/build due to the weather, to give the current kit the night off an go and enjoy the new issue of TMMI, so not a total loss. :)

Thoughts? Please discuss...

  • Member since
    January 2003
  • From: Peoples Socialist Democratic Republic of Illinois
Posted by Triarius on Wednesday, May 24, 2006 10:14 PM
Humidity will only affect the rate of solvent loss, and since most of your solvent is Isopropyl 90%, humidity is less of a problem.

However, the excess moisture in the air will have a surface effect on acrylics. You can remedy this with good air circulation (AFTER the paint is tack free, or you'll collect some dust) and a gentle heat source.

I prefer to paint in humid conditions. I'd rather have paint dry and cure more slowly, than before I can get it to the model surface.

Ross Martinek A little strangeness, now and then, is a good thing… Wink

  • Member since
    December 2004
Posted by vfxart on Wednesday, May 24, 2006 10:24 PM
Oh... huh.

Well, all right... to be sure I get you: the alcohol plays into my favor, and I want to circulate a bit of air around the model afer the paint has set up a bit and isn't so likely to collect any stray dust.

Other than that, the humidity does a bit of what a retarder or extender might do? (Though probably to a much less controllable extent...)

Thanks for the reply, and though I'm tempted to run downstairs and bring up some parts (I primer and spray anything canned down there...) I think I'll still hold off for tonight, but this is good to know.

  • Member since
    January 2003
  • From: Peoples Socialist Democratic Republic of Illinois
Posted by Triarius on Wednesday, May 24, 2006 11:19 PM
Humidity helps "lay" airborne dust. Because you reduce (thin) the paint with something besides water, gas laws work in your favor. But remember that these paints do still contain water as a solvent, and high humidity still slows the loss of that solvent. So they will dry more slowly, especially at the surface where they are in contact with damp air. Hence, air circulation helps.

However, curing (not the same as drying) is temperature dependent—warmer is faster, and also reduces relative humidity.

As a rule of (paint splotched) thumb, I generally wait overnight to a full day between coats unless I use a heat cure by borrowing my wife's food dehydrator.

Patience is almost always a virtue. Wink [;)]

Ross Martinek A little strangeness, now and then, is a good thing… Wink

  • Member since
    February 2003
  • From: Tacoma WA
Posted by gjek on Wednesday, May 24, 2006 11:23 PM
I build armor kits so gloss paint schemes are not an issue. I am from Florida and even on humid days I didn't notice any problems with how the paint looked when it had dried. However humid days always caused anxiaity( sorry about the spelling) about moisture causing water drops, even with a water filter. That was why I went to using CO2.
Msgt USMC Ret M48, M60A1, M1A1
  • Member since
    February 2003
  • From: Southern California, USA
Posted by ABARNE on Thursday, May 25, 2006 12:52 AM
Unless you're at 100% humidityWink [;)], I wouldn't worry about it too much for your paint.  Do make sure that you have your moisture trap situation well in order.  A few months ago while painting during some wet, humid weather, I had a bit water shooting out my airbrush, something that had never happened previously.  So to be safe, I added a second inline moisture trap.  Fortunately, I was shooting acrylic so the moisture didn't kill the finish.  On the otherhand, aside from the airbrush spitting water, I had no issues with how the paint dried and cured.
  • Member since
    July 2004
  • From: SETX. USA
Posted by tho9900 on Thursday, May 25, 2006 7:04 AM
Vallejo doesn't use alcohol as an ingredient and you can't thin with it..  that said I have never had a problem using Vallejo in humidity (I live between bayous and the Gulf of Mexico so it's pretty humid here...)
---Tom--- O' brave new world, That has such people in it!
  • Member since
    December 2004
Posted by vfxart on Thursday, May 25, 2006 10:32 AM
I am trying to remember what I've done for the Vallejo when I've used it, but now I think on it, could be that I've always used their thinner... which is odd because I'd have sworn that I've used the iso in it as well as using that in the Tamiya mixes.

Thanks again for the replies... I found I was able to take care of a little bit last night (cooler and drier in the garage, so a quick set-up got me some spraying time), and the results seem fine this morning.

I do have a good regulator/filter (only took me 3 months or so to find the little beast) and I'm pretty confident with it. Just being in the midwest now provides for a few slightly humid days, and I'd like to avoid downtime....

Will have to wrack my brain more on the V/iso thought... wonder if I've gotten away with something for a while.
  • Member since
    July 2004
  • From: SETX. USA
Posted by tho9900 on Thursday, May 25, 2006 7:23 PM
I've tried thinning Vallejo with Tamiya thinner for a test and it all clumped together as soon as the thinner hit it... being that their thinner contains alcohol I would think that was it... I use Vallejo thinner consistently and love the results!!!  I've tried distilled water but it didn't seem to work quite as well as their thinner...
---Tom--- O' brave new world, That has such people in it!
  • Member since
    December 2004
Posted by vfxart on Thursday, May 25, 2006 10:03 PM
Thanks again, Tom. I do like their thinner.

btw, I've gotten a lot out of the Vallejo thread that's currently going as well, so thanks for jumping in there too. I'll be getting back to things here in a bit, fingers crossed...
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