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Why isn't my Butyrate Dope (Brodak) glossy??

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Why isn't my Butyrate Dope (Brodak) glossy??

Old 03-23-2024, 01:10 PM
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aaganz
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Default Why isn't my Butyrate Dope (Brodak) glossy??

I am testing my Butyrate Dope (Brodak) on a small frame sample of Silkspan before brushing onto the new wing covering. It is "Cessna White" but dries to a flat, dull off white color. Where is the gloss, and how do I get that?

As a kid, all the dope was just painted on (airplane and ship models) and always dried to a shiny surface??

I'm not trying to be a "perfectionist", as I expect the plane to crash as I re-learn how to fly it again after 50 years, but do want a mode I can be proud of!!
Thanks for any insight.
aaganz
Old 03-24-2024, 07:35 AM
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hag
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Butyrate dope is generally a non glossy finish. When used on full size airplanes, its the finish Cubs, Champs and the like had. That's why so many rebuilders like the urethanes (Air Tech is popular theses days). For models, a shiny finish on dope was traditionally done by hand rubbing using rubbing compound. It's a time consuming process, but the results can be stunning. Many switched to clear-coating to save all that hard work. I actually like the not quite glossy finish of dope on my silkspan covered models.
Old 03-24-2024, 08:55 AM
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I replied to your other thread but I will say something here as well. Hag is on point about the hand rubbed finish. One thing about high gloss is that you are laying on enough paint to fill the grain of the silkspan plus enough to sand it to a super smooth finish. It is easy to add a significant amount of weight with a super glossy paint job.
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Old 03-24-2024, 02:10 PM
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aaganz
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Thanks to Hag and Matt. Rubbing would need too many layers of dope. I have ordered 4 oz of clear dope, and will add that on at the end with some thinner and hope for a reasonably glossy finish! I want a nice looking plane in the event it only gets a few demonstration flights!
aaganz
Old 03-25-2024, 01:20 PM
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aaganz
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All,

I posted the question to Brodak, and they replied today. They said to apply 2-3 coats of clear butyrate dope over the color dope, and that would do it. The shipment pf clear dope will be here in a day or so, and I can test it on my "test frame sample".
aaganz
Old 03-26-2024, 05:51 PM
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I have always used Randolph dope Nitrate And Butirate, temperature is important 70 degrees is about right, use retarder and a little MEK or Tauall in the mixture. Always have a nice gloss, AJ
Old 03-28-2024, 11:26 AM
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All,
I am trying out the clear dope Brodak just sent me. Form various YouTubes, I see that some paints are intended to be put on in (at least ) 2 layers. The bottom layer is the "color layer", and the outer layer is the "gloss layer". I never did this in 2 steps as a kid....we just put on whatever dope came from the local hobby store.
See my next post with pix of the plane (1953) , as retrieved from the attic last month.
aaganz
Old 03-29-2024, 09:00 AM
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The "clear/base" is primarily an automotive paint thing. But it does work with dope. For the purposes of polishing and gloss dope is essentially a lacquer. As long as your dope is specifically "clear gloss" you should be able to achieve a nice finish. Multiple thinned coats are better than one heavy one. As modelers we are relatively lucky. Just for perspective, I have a aircraft repair manual from the 1940's. It describes 19 coats of dope for a high quality covering job.
Old 03-30-2024, 10:25 AM
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How did you guys ended up with some gloss in your dope? I recently decited, to go order a quart of silver dope. Kinda having a difficult time getting good coverage getting lite streaks in my Maroon even the Metalic Maroon is streaking. Figure brushing is out. And I will go to my Develbus top loader. HVLP touch up gun.
Old 03-31-2024, 08:32 AM
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Originally Posted by AJ Sun
How did you guys ended up with some gloss in your dope? I recently decited, to go order a quart of silver dope. Kinda having a difficult time getting good coverage getting lite streaks in my Maroon even the Metalic Maroon is streaking. Figure brushing is out. And I will go to my Develbus top loader. HVLP touch up gun.
When you say "streaks" do you mean that the silver is bleeding up through the maroon? If so, the solvent in the maroon is probably re-dissolving the silver. The spray gun is probably your best bet but even so, giving the silver an extra day or two to dry may help. Even after it is dry enough to sand I can still smell solvents coming off of butyrate dope.
Old 04-01-2024, 09:55 AM
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All,
I am getting a good gloss with the Brodak Clear Dope brushed over the Cessna White Dope. At first the brush strokes stood out as "streaks", but then filled in gradually to a smooth finish. I am now brushing on the "yellow stripes" on the wing and elevator, just as the original plane was years ago. Then will cover it all with Clear Dope....I am checking there are no interactions among all the dopes!
When the RCuniverse system allows, (failed so far!!) I will post a pix of the old, torn up, CL plane. I do want to know what it was ....obviously popular in the mid 1950s
aaganz
Old 04-01-2024, 10:36 AM
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Ya that's happened to me to. Glad she smoothed out. I just ordered a quart of Silver non taughting dope need to do more fill, not really concerned about added weight. Like a slow circle getting old for this S***. But really enjoy the circle. And keeping my lines tight!!!!AJ.
Old 04-01-2024, 12:58 PM
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Originally Posted by AJ Sun
Ya that's happened to me to. Glad she smoothed out. I just ordered a quart of Silver non taughting dope need to do more fill, not really concerned about added weight. Like a slow circle getting old for this S***. But really enjoy the circle. And keeping my lines tight!!!!AJ.
I hear you AJ. The older you get the harder it is to stay in the circle.

Has anyone touched on humidity and dope? Dope and other lacquers will sometimes blush (take on a whitish haze) if the humidity is high. Unless it is really bad it will generally clear over a couple of days as the dope continues to dry.
Old 04-01-2024, 05:45 PM
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The two things that contribute to blushing are high humidity (as was already mentioned) and solvents in the dope (lacquers) that evaporate too quickly, causing moisture to be trapped in the paint. The solution is to use a "retarder" (low grade thinner) to slow the rate at which the paint dries. Years ago companies like Testors, and Aero Gloss sold retarders, but I don't think any model dope supplier does so today. A good automotive paint supplier should have compatible retarders.
Old 04-02-2024, 06:09 AM
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You can get Randolph universal retarder. It's about $25 bucks a quart. Search for Y-9910 Universal Retarder and it will come up at Aircraft Spruce and other vendors.

Gloss is going to be a function of how fast it dries. The faster it dries, the flatter the finish.

Chris
Old 04-02-2024, 10:02 AM
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Wow, you learn something every day! I thought colored dope was used more as a primer base instead of an actual finish. I had applied about an entire gallon of Brodak butyrate dope in many coats onto an 89" koverall covered plane and kept sanding between coats until the cloth and dope was sealed and smooth. Then with a spray gun I applied coats of fuel proof primer, sanding the primer, then applying final top coat paint for a nice finish.

I never knew colored dope would dry with a deep enough pigment to look good....and always thought it was used more for colored primer purposes.
Old 04-03-2024, 08:24 AM
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Originally Posted by rustyrivet
Wow, you learn something every day! I thought colored dope was used more as a primer base instead of an actual finish. I had applied about an entire gallon of Brodak butyrate dope in many coats onto an 89" koverall covered plane and kept sanding between coats until the cloth and dope was sealed and smooth. Then with a spray gun I applied coats of fuel proof primer, sanding the primer, then applying final top coat paint for a nice finish.

I never knew colored dope would dry with a deep enough pigment to look good....and always thought it was used more for colored primer purposes.
You aren't completely wrong. A lot of colored dopes, especially reds and yellows are translucent and are a part of a layered process. Unless you are going for the translucent look, which can be very attractive, some colors require a base coat of silver or white. It may still take multiple coats to get the desired level of color saturation. One method was to start with thinned nitrate dope to adhere and shrink the covering. You want it to be thinned enough to soak through and onto the underlying structure. This is followed by thinned dope mixed with a filler, often talcum powder, that fills the grain of the covering and can be sanded to a smooth surface. The filler will save sanding of the color coats since they will go on more smoothly. From here you can proceed with silver, white or other opaque dope and whatever translucent color you like. In general it is lighter colors first followed by dark shades. Dark colors will show through light colors, even with lots of coats. A single opaque basecoat can save a lot of coats of color, along with sanding and added weight. With good prep work you will only need a clear coat to even out the gloss.

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