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  #11  
Old 03-16-2016, 11:01 AM
samb samb is offline
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Quote:
Originally Posted by clhug
...

Actually, now that I think about it more, even beyond the primer, what about just the regular spray paint? I've always used Testors paint. Is there a reason to prefer this vs. just regular Krylon or Rust-o-leum spray paint? I'm sure it's cheaper (probably the same price for 2 or 3 times the size of spray can)? Certain colors I'm guessing I can probably really only find in the model spray paint, but for basic black, white, red, blue, green, would just Krylon or Rust-o-leum do fine?

Thanks again!


As you say, Testors in those little (3 oz. ?) hobby shop cans is the expensive way to go. I only go there if I need a particular color that I can't get in the bigger and more economically priced cans.

FWIW I've been using Rusto Painters Touch 2x from the Depot and Wally World. I've been seeing alot of the Krylon ColorMaster line at the Walmarts around me as well so I intend to try that sometime soon.

Hope this helps.
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  #12  
Old 03-16-2016, 02:31 PM
chrism chrism is offline
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Quote:
Originally Posted by clhug
Thanks for all the feedback, but most of it is really overkill for me. I'd really like to get back to the original basic question.

Yes, back when I built rockets regularly as a kid, I finished all balsa parts using coats of Aerogloss, sanding between coats. That's what I expected to keep doing when I recently started building again, so I was a bit surprised when the instructions in the kits I bought recently said to use primer paint instead of aerogloss. So I thought I'd give the primer a try.

I'm not a perfectionist by any means. I'm not going to put the time and effort in that some have described using various suggested methods. For me, I'm either sticking with the aerogloss, or going to try just regular spray in a can primer.

So going back to the original question, if I want to do the primer, can I just use regular Krylon or Rust-o-leum primer in a spray can, or is there is a specific modeler primer paint I should look for? I looked on the Testors paint rack at the hobby shop and didn't see a primer. The instructions don't give any detail about any specific primer.

Actually, now that I think about it more, even beyond the primer, what about just the regular spray paint? I've always used Testors paint. Is there a reason to prefer this vs. just regular Krylon or Rust-o-leum spray paint? I'm sure it's cheaper (probably the same price for 2 or 3 times the size of spray can)? Certain colors I'm guessing I can probably really only find in the model spray paint, but for basic black, white, red, blue, green, would just Krylon or Rust-o-leum do fine?

Thanks again!



You may consider investing in an airbrush, especially if you want to paint low power rockets. There is a variety of colors available to spray more so than the few colors you may find at the hardware store and a lot cheaper than Testors or Tamiya model spray paints.
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  #13  
Old 03-16-2016, 04:15 PM
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There IS a 'modeler's' primer; just what I spoke of- Aero Gloss Balsa Fillercoat and Sanding Sealer.
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  #14  
Old 03-16-2016, 06:27 PM
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Quote:
Originally Posted by kevinj
Get a primer that is compatible with your finish coats. Usually I get the primer made by the same company as the paint. Look for "sandable" or "high fill" primers.

kj


It certainly is a safe practice to use the same brands, but I've never had compatibility problems between primers and subsequent top coats. I've sprayed almost every imaginable brand of enamels, and several types of lacquers, over the three primers I listed earlier.

BUT ... make sure the primer coat is dry. I wait at least 24 hours after primer coats, and longer if I can still detect an odor, meaning it is still outgassing solvents.
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  #15  
Old 03-16-2016, 07:35 PM
clhug clhug is offline
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Thanks again everyone!

I stopped at Home Depot on the way home from work tonight and found the Rust-oleum Painters Touch 2X Ultra Cover primer so I bought the flat white. I'll give that a try.

Thanks also for the info about regular paint.
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  #16  
Old 03-16-2016, 08:45 PM
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I'd give the Painters Touch paint a try, too. I really like the way they go on, much better than Rustoleum spray paints from years ago. I'm not a huge fan of the new Krylons, maybe because the old Interior/Exterior type from about 10 years so was so good, and then it got replaced with the inferior (IMHO) Indoor/Outdoor type.
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Last edited by LeeR : 03-17-2016 at 12:00 AM.
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  #17  
Old 03-18-2016, 02:49 PM
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luke strawwalker luke strawwalker is offline
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The Walmart "Color Place" red and grey primers do an excellent job for me, and they're 99 cents a can...

Otherwise, I use the Rustoleum high fill autobody wet sandable primer... good stuff!

later! OL J R
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  #18  
Old 03-18-2016, 05:57 PM
clhug clhug is offline
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Two more follow-up questions.

For primer, does it matter whether to use flat or glossy primer? I was thinking flat would sand better, but maybe it doesn't make a difference? Any other reason to use flat vs. glossy primer? Flat primer won't interfere with using glossy top coat, or vice versa, will it?

I also see people mention, and the primer I bought says, wet/dry sandable. What exactly does wet sandable mean? Does that mean able to be sanded before the paint itself dries, or that it can be sanded with a bit of water after the primer dries? Either way, why would one do wet sanding?

Thanks again!
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  #19  
Old 03-18-2016, 06:07 PM
chrism chrism is offline
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Quote:
Originally Posted by clhug
Two more follow-up questions.

For primer, does it matter whether to use flat or glossy primer? I was thinking flat would sand better, but maybe it doesn't make a difference? Any other reason to use flat vs. glossy primer? Flat primer won't interfere with using glossy top coat, or vice versa, will it?

I also see people mention, and the primer I bought says, wet/dry sandable. What exactly does wet sandable mean? Does that mean able to be sanded before the paint itself dries, or that it can be sanded with a bit of water after the primer dries? Either way, why would one do wet sanding?

Thanks again!



All primers have a flat finish which helps the top coat to adhere better. Wet sanding is done when the primer is completely dry, wet the sand paper in some water (not too wet) and sand, The water helps the sand paper not become too clogged with sanding dust. You don't have to wet sand. Most modelers find what works for them. I usually dry sand, using finer grits to get a smooth finish.
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  #20  
Old 03-19-2016, 10:58 AM
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As to the flat/glossy question-- I don't have any experience there, but I don't really think it should matter much... that said, I'd stick to flat. Flat SHOULD have a higher solids (and probably slightly larger particles) count and therefore cover up and fill in stuff better. Just stay away from the stupid "paint and primer in one" materials... Those are just counter to everything that needs to be done to get a good finish-- they're a "one step" product for lazy guys, IMHO... the whole purpose of priming is filling in minor imperfections and the surface being sanded down smooth PRIOR to paint... How do you sand the primer if it's IN the paint?? Plus, you can't put a heavy load of primer solids in the paint without compromising the color and consistency and applicability of the paint, yet the flowability of the paint is hampered by the solids of the primer anyway... Yechh-- what a mess... stuff can't do EITHER job right IMHO...

No, the finish of the primer has no effect on the final "finish" of the paint (meaning whether it's glossy or flat finish paint). The primer's job is to transfer as much "solids" (particles in a solvent) to the surface being finished as possible, to flow out and fill as many imperfections as possible, to promote adhesion between itself and the surface being finished, and promote adhesion of the paint layer going over it to itself and the surface, and to be sandable enough to allow the surface blemishes to be sanded smooth to hide their presence. Paint, OTOH, is simply pigments in a solvent designed to provide color. PAINT DOES NOT HIDE FLAWS, IT MAGNIFIES THEM!!! Whatever your surface looks like when you're done priming and sanding, is about what it'll look like when it's painted; if you can see imperfections in your primer coat after sanding, you WILL see them after painting. Many people mistakenly believe that paint will hide imperfections, that even if they can see imperfections after priming and sanding that they'll somehow 'disappear' when the paint is applied, that "the paint will cover it up". This isn't true. BASICALLY, THE APPEARANCE OF THE FINAL FINISH IS HOW IT LOOKS BEFORE THE PAINT IS APPLIED... IOW, if you can see imperfections, flaws, etc in the sanded primer BEFORE you paint, you will almost certainly see them AFTER painting.

"Wet sandable" primer is designed to be sanded using water. "Dry sandable" primer is not designed for this. "Wet sanding" is a process used to make professional-grade finishes on things like show cars and stuff like that, where you want that "wet look" or "mile deep" paint job... Typically it's done by using a garden hose just dribbling water on the surface being sanded while the surface is sanded with a fine-grade sandpaper using a long sanding bar to get the surface COMPLETELY SMOOTH and level and even. The purpose of the water is to cool and lubricate the sandpaper and to flush away sanded off particles to prevent these very-fine-grit sandpapers from clogging up with particles. Dry sanding liberates a lot of particles in the form of sanding dust... wet sanding takes those particles away in water. Sanding also creates heat via friction, and can make the primer sticky and gummy, gumming up your sandpaper and clogging it with particles, making it worthless. Wet sanding can carry this heat away, prevent the gumminess, and flush the particles from the paper preventing clogging of the paper.

Now, obviously using true "wet sanding" principles with a dribbling garden hose water source isn't practical for most model rocketry applications (particularly paper tubes and wood fins, although fiberglass and other waterproof materials certainly CAN be wet-sanded) due to the nature of the materials (paper tubing and wood fins/cones). BUT, we can use a variation of the method that produces near FLAWLESS results... I call it "damp sanding". I start by hardening my balsa cones and transitions with ultra-thin CA glue wicked into the surface... take it outside (so the fumes don't run you out of the house) and wet the surface of the cone/transition with ultra-thin CA glue, which will wick itself down into the wood grain of the balsa like a sponge soaking up water. There it will cure and "harden" the balsa, much like fiberglass impregnated with resin. This helps toughen the cone so it's not AS prone to damage (as an unhardened one). Doesn't make it "bulletproof" but it DOES help... Sand down the "grit" and "fuzz" raised by the CA with 220 grit paper, then I brush on a layer of Elmer's Carpenter's Wood Filler thinned down to about the consistency of hot dog mustard with a few drops of water worked into a dab of it in a small disposable bowl with the brush. Let this dry a couple hours, then sand it down with 220 grit paper followed by 400 grit paper to fill and eliminate the wood grain and large surface imperfections. Then I give it 2-3 progressively heavier coats of primer, allow to dry fully (overnight is best, longer depending on your climatic conditions at the time, but I HAVE sanded within just a few hours on occasion...) Sand with 220 grit paper followed by 400 grit paper, dry. Carefully inspect the surface, looking for any major imperfections such as low spots, waviness, high spots where the primer was sanded through to the bare surface, etc. If necessary, reapply more primer and allow to dry and sand again... though usually this isn't necessary if you'd done things right up to this point. Sometimes just hit a light coat of primer on any 'high spots' where the primer sanded through. Now, you're ready to either 1) call it good and paint or 2) damp sand.

To be continued...

OL J R
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