Ye Olde Rocket Forum

Go Back   Ye Olde Rocket Forum > Work Bench > Building Techniques
User Name
Password
Auctions Register FAQ Members List Calendar Today's Posts Search Mark Forums Read


Reply
 
Thread Tools Search this Thread Display Modes
  #1  
Old 05-30-2011, 04:41 PM
brockrwood's Avatar
brockrwood brockrwood is offline
...it obstructs my view of Venus...
 
Join Date: Nov 2007
Location: Denver, CO
Posts: 18
Default Spray paint goes on "dusty" or "sandy"

OK, what am I missing?

When I paint a rocket, the paint tends to go on so that the finish seems like it has paint "dust" or "sand" on it, rather than a nice smooth finish.

What am I doing wrong? Not putting on enough primer? Using too much primer? Not sanding enough? Spraying from too far away? I am using standard Krylon white primer and Krylon flourescent yellow on top of that.

Any help appreciated. My 9 year old daughter, who used to think I knew everything about rockets, has now lost faith in my rocket painting ability.

Help! My "street cred" with my offspring is at stake!

- Brock
__________________
Brock R. Wood, NAR 87453; Playing with model rockets since the purchase of an Estes "Launcher's Special" parts assortment in 1976.
Reply With Quote
  #2  
Old 05-30-2011, 05:15 PM
jharding58's Avatar
jharding58 jharding58 is offline
Master Modeler
 
Join Date: Apr 2007
Location: Kennesaw, GA
Posts: 1,932
Default

The most common cause of a rough finish with rattle can spray paint is either being too far away or crazy low humidity. If the surface is well prepared and smooth (a very big if) then the issue with a spray is paint partially drying in the aerosol; small droplets dry prior to hitting the surface to be painted.

When the manufacturer provides the "hold can" distance it is usually appropriate for a well shaken/mixed product in the optimal temperature and humidity as referenced on the can. Check the painting conditions on most paints and there is a temperature range and a maximum humidity - Krylon and Rustoleum want it below 85%. If it is very, very dry then you will see little globules of paint drying on the surface as opposed to forming a paint layer.

Also make sure that the paint is really well shaken from a rattle can. As a resolution to this model try taking a 400 - 600 grit paper to the model and re-apply a coat when it is a little cooler and perhaps a little less dry.
__________________
Gravity is a harsh mistress
SAM 002
NAR 91005
"The complexity of living is eminently favored to the simplicity of not."
Reply With Quote
  #3  
Old 05-30-2011, 05:33 PM
brockrwood's Avatar
brockrwood brockrwood is offline
...it obstructs my view of Venus...
 
Join Date: Nov 2007
Location: Denver, CO
Posts: 18
Red face

Thanks for the tips!

Yes, it is really dry here in Denver on most days but, oddly, it has been sort of rainy lately. I will try shaking it *really* well and holding it a bit closer. That is sort of what it seems like - the paint actually drying before it hits the rocket and then adhering as little dust particles.

I am starting to appreciate the "almost ready to fly" rockets with the pre-colored parts more and more as I sand and sand and re-paint and re-paint.

This is the free rocket my daughter got from Quest for joining the NAR. Maybe I should just slap the decals on it, stick a C6-5 in it, and push the button! No, my "do it right or don't do it at all" superego is taking over...

- Brock




Quote:
Originally Posted by jharding58
The most common cause of a rough finish with rattle can spray paint is
either being too far away or crazy low humidity. If the surface is well prepared and smooth (a very big if) then the issue with a spray is paint partially drying in the aerosol; small droplets dry prior to hitting the surface to be painted.

When the manufacturer provides the "hold can" distance it is usually appropriate for a well shaken/mixed product in the optimal temperature and humidity as referenced on the can. Check the painting conditions on most paints and there is a temperature range and a maximum humidity - Krylon and Rustoleum want it below 85%. If it is very, very dry then you will see little globules of paint drying on the surface as opposed to forming a paint layer.

Also make sure that the paint is really well shaken from a rattle can. As a resolution to this model try taking a 400 - 600 grit paper to the model and re-apply a coat when it is a little cooler and perhaps a little less dry.
__________________
Brock R. Wood, NAR 87453; Playing with model rockets since the purchase of an Estes "Launcher's Special" parts assortment in 1976.
Reply With Quote
  #4  
Old 05-30-2011, 06:37 PM
Doug Sams's Avatar
Doug Sams Doug Sams is offline
Old Far...er...Rocketeer
 
Join Date: Mar 2005
Location: Plano, TX resident since 1998.
Posts: 3,802
Default

Quote:
Originally Posted by brockrwood
OK, what am I missing?

When I paint a rocket, the paint tends to go on so that the finish seems like it has paint "dust" or "sand" on it, rather than a nice smooth finish.

What am I doing wrong?
Yes, as noted, you ain't getting it wet enough. You're shooting from too far away, and you're not putting enough paint on. It's gotta get it wet if it's gonna look good.

Trying hold the can closer and apply more paint. You don't want to dwell with the can - keep it moving. But come back over the same area with multiple passes to get it wet.

To avoid runs, apply a tack coat first. This is a light, sorta dry coat. Let sit for 10 minutes. Then apply a heavier second coat wherein you lay it on thick. The first coat, having partially dried, will help hold the second, thicker coat and prevent runs.

Then wait 10 more minutes. If it still needs paint - if it has some poorly covered areas - then apply a 3rd coat using the same techniques as the second.

HTH.

Doug

.
__________________
YORF member #11
Reply With Quote
  #5  
Old 05-30-2011, 06:39 PM
brockrwood's Avatar
brockrwood brockrwood is offline
...it obstructs my view of Venus...
 
Join Date: Nov 2007
Location: Denver, CO
Posts: 18
Default

OK, I just re-painted with the can held about 1/2 the distance I normally use and it worked *much* better. No more dusty, powdery stuff! I think I was mis-judging the distance between the paint can nozzle and the rocket previously.

Paint problem solved by actually getting the paint onto the rocket before it dries in the air. Doh!

Thank you!

- Brock


Quote:
Originally Posted by jharding58
The most common cause of a rough finish with rattle can spray paint is either being too far away or crazy low humidity. If the surface is well prepared and smooth (a very big if) then the issue with a spray is paint partially drying in the aerosol; small droplets dry prior to hitting the surface to be painted.

When the manufacturer provides the "hold can" distance it is usually appropriate for a well shaken/mixed product in the optimal temperature and humidity as referenced on the can. Check the painting conditions on most paints and there is a temperature range and a maximum humidity - Krylon and Rustoleum want it below 85%. If it is very, very dry then you will see little globules of paint drying on the surface as opposed to forming a paint layer.

Also make sure that the paint is really well shaken from a rattle can. As a resolution to this model try taking a 400 - 600 grit paper to the model and re-apply a coat when it is a little cooler and perhaps a little less dry.
__________________
Brock R. Wood, NAR 87453; Playing with model rockets since the purchase of an Estes "Launcher's Special" parts assortment in 1976.
Reply With Quote
  #6  
Old 05-30-2011, 06:43 PM
brockrwood's Avatar
brockrwood brockrwood is offline
...it obstructs my view of Venus...
 
Join Date: Nov 2007
Location: Denver, CO
Posts: 18
Default

The people in this forum rock. You are all very helpful. Thank you!

My "street cred" with my daughter is saved!

- Brock
__________________
Brock R. Wood, NAR 87453; Playing with model rockets since the purchase of an Estes "Launcher's Special" parts assortment in 1976.
Reply With Quote
  #7  
Old 05-30-2011, 09:28 PM
Solomoriah's Avatar
Solomoriah Solomoriah is offline
Incorrigible Kit Basher
 
Join Date: Jul 2006
Posts: 1,818
Default

I find that I do most of my spraying from 4" to 8" away, not the 12" usually recommended. But low humidity is rarely a problem here...
__________________
SAM #0076 Licensed to Build
My site: http://rocketry.gonnerman.org
Reply With Quote
  #8  
Old 05-31-2011, 08:38 PM
Mark II's Avatar
Mark II Mark II is offline
Forest Sprite
 
Join Date: Dec 2006
Location: Back Up in the Woods
Posts: 3,657
Default

If, like me, you do your spray painting outdoors, beware of breezes. Aside from the obvious, another problem they can cause is the one that you reported. My area always has variable winds that swirl around from random directions, so I have learned to wait for moments of calm when I paint. Early on though, I didn't always stop soon enough after the wind picked up again, and I got gritty paint coats as a result.

Another thing: apply the paint in one smooth steady stroke from end to end in one direction only, keeping the pace moderate and constant from beginning to end, and maintaining the same distance throughout. It often helps to start the spraying just ahead of the rocket and stop it after you have gone past the other end. Then rotate the rocket a quarter turn or so and repeat the process. Continue until the rocket is fully covered with an even coat. Jerking or jiggling the can around as you spray is another way to obtain a gritty coat and spattering of paint. Sudden movements cause momentary surges and ebbs in the amount of paint that is delivered to the nozzle. To lay down an even coat, you need to have a constant, even fan or cone of spray from the nozzle, and to deliver it the nozzle requires a steady flow of paint from the can.
__________________
Mark S. Kulka NAR #86134 L1,_ASTRE #471_Adirondack Mountains, NY
Opinions Unfettered by Logic Advice Unsullied by Erudition Rocketry Without Pity
+09281962-TAK-08272007+
SAM # 0011
Reply With Quote
  #9  
Old 05-31-2011, 08:58 PM
Solomoriah's Avatar
Solomoriah Solomoriah is offline
Incorrigible Kit Basher
 
Join Date: Jul 2006
Posts: 1,818
Default

I'm right handed (when painting, at least) and I always try to stand with the breeze at my right elbow. That way, the paint goes toward the rocket (held in my left hand).
__________________
SAM #0076 Licensed to Build
My site: http://rocketry.gonnerman.org
Reply With Quote
  #10  
Old 05-31-2011, 10:57 PM
LeeR's Avatar
LeeR LeeR is offline
Retired with Way Too Many Kits
 
Join Date: Jun 2007
Location: Colorado
Posts: 1,501
Default

I think some of your problems could be the Krylon fluorescent paint. They tend to go on a little flat, with some graininess. I have seen similar results with Rustoleum. And I've gotten great results with both brands for regular and metallic colors.

It would be interesting to hear if you have much better results with non-fluorescent paint.
__________________
Lee Reep
NAR 55948, L2

Projects: Super Saros, Honest Johns (new, and Maxi), Mars Snooper (BMS), yet another Booster-55 $3 rocket
In the Paint/Detailing shop: Estes Saturn 1B
Completed!: Semroc Mars Lander, Super Orbital Transport (scratch-built), Interceptor-E
Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump



All times are GMT -5. The time now is 06:59 AM.


Powered by: vBulletin Version 3.0.7
Copyright ©2000 - 2017, Jelsoft Enterprises Ltd.
Ye Olde Rocket Shoppe 1998-2017