stunthanger.com
Building Tips and technical articles. => Paint and finishing => Topic started by: Avaiojet on March 30, 2013, 11:33:51 AM
-
I can deal with the rapid drying time that dope has. I don't like it, but I can deal with it.
Has anyone used "retarder" with dope with any success? If so, which brand worked well.
I must add, I'm using clear dope, so my question would be related to clear dope.
Thanks in advance.
Charles
-
Charles - It all depends on the brand / compatibility of the dope you are using with standard available thinners. The dope pretty much has one speed, and the thinner determines the set. If the dope you use can be thinned with auto thinners, then get some acrylic lacquer slow rated thinner (not the cheap stuff for cleaning brushes)
Retarder is probably made mostly of the same chemical that makes slow thinners slow, but concentrated. You have to be very careful using it, as it's easy to go overboard and you can melt a plastic canopy with the stuff, as well as your previous layers of dope come bubbling up. I'd personally rather use a slow rated thinner that way it is essentially pre-mixed with retarder to the correct amount for you.
In sunny Florida, I like slow thinners in the summer, medium in the winter, and almost never fast. This is because the ambients do effect the cure time. A slow thinner used on a cold winter day could be disastrous, where the same thinner would work fine on a sunny summer day. One might think slower is always better, since it will have more time to level out and less chance at trapping moisture and blush. There is such thing as too much of a good thing here, because if it's too slow, then it will have time to eat/dissolve down into previous layers (very bad when shooting trim colors or clear coats over final paint scheme) especially if you are the kind who likes to gun on a heavey wet coat rather than build up several lite coats.
So, like all things in stunt, it's an acquired talent to get a feel for when to use what. It's like looking out the window and at your calendar and knowing exactly where to go fishing today and what's running and what bait they will hit. Only experience will get it to be second nature.
EricV
-
Drying time depends on ambient temperature/humidity (barometric pressure?) It varies. Different brands of dope/thinners also vary in dry time. Then there is high tautening dope and non-tautening dope. Never use tautening dope mixed for full sized aircraft. The shrinking properties are powerful. Which means it will warp wing panels into a pretzel. High tautening dope mixed by Sig (Supercoat?) is ok for wing panels, only until the covering is shrunk. Problems happen when drying is too fast or too slow. Fast drying means orange peal lumping or alligator bumps. Too slow and the dope melts through too far to lower layers of paint, which means you may start seeing primer color leaking or uneven color. Bad news. I almost always stay with the brand of thinner matched to the brand of dope for a given layer of paint. I mix the dope thinner/ dope color or clear around 50/50 then do a test pattern. This is a must. Even when spraying on the same day. Spraying conditions may vary during the day. If it is drying too fast, I splash in some retarder, and test again. If I see runs I add more dope. How much dope/thinner/retarder? Depends on how that test panel looks. I use a touch up gun with .8 mm to 1 mm needle/nozzle. Distance between the nozzle and surface to be painted also effects dope drying/set up. For my guns my spray distance is about 8" to a foot. Never use more than 10% of retarder. I never need or use even that much. The scientific splash... I thought retarder was a non-thinner substance. Certainly smells different from thinner. Then there this is the use of doing a dusting coat or a wet coat or... Your dusting/misting/wet coat differs of course from mine. Test panel/test panel did I mention it's a good idea to test each mix before your shoot.
-
I routinely use a little retarder. I've used Sig retarder with several brands of dope with no problem. Always a good idea to make a test on a non essential item.
-
Here we are the opposite. You need slow thinners in winter (due to the humidity level) and medium thinner in the summer (somewhat lower humidity - sometimes). I've never really used retarder except when the humidity is very high and then just a very little.
-
I have used a plasticiser like castor or banana oil in the past and that seemed to slow down the evaporation of the thinners somewhat.
Or you could try " SIGDR001 SIG DOPE RETARDER 4 OZ."
-
Charles,
To slow down the dope you should use a thinner for high temperature and mix 60/40 thinner/dope. The retarder is really for humidity hazing reduction. If you use more than about 8% the dope doesn't dry hard and stays rubbery.
Best, DennisT
-
Trying to paint with dope here in Florida during the late spring, summer, or early fall without retarder without blushing is nearly impossible. I've used Sig dope, with Sig thinner, along with about 10 % retarder. Unfortunately my quart can of retarder leaked, which is one of the reason I switched to Rustoleum, and Duplicolor.