Primer Crinkling

[hball55]

This is a new plastic nosecone no other paint present. However every time I try to spray primer on the nosecone, there's one spot that the primer keeps crinkling. I sand it down smooth, spray the spot again, and the primer continues to crinkle in that one spot. I'm using Walmart (HomeShades) gray primer. I suppose I could try another brand, but it just puzzles me that this continues to happen.

 

[rharshberger]

Paying attention to see what answers you get. We have some folks who really seem to know their paint.

 

[K'Tesh]

Did you wash the nosecone with soap and water? There may be release agents still present on the part that the paint doesn't like.

 

[o1d_dude]

There are special primers for plastic car bumpers and such. Even lowly Rustoleum makes a "Plastic Primer" that can mostly be found in car parts chain stores like Kragen/O'Reilly's/Autozone, etc.

Might be worth a shot as it has always worked for me. Even on those Madcow Rocketry nose cones that everyone says won't hold paint.

 

[hball55]

Did you wash the nosecone with soap and water? There may be release agents still present on the part that the paint doesn't like.

The release agent thought makes me think. Perhaps I didn't clean that small area well enough. I suppose the sanding of that area might not cure the problem. I was also thinking that oil from my hand might be the culprit too.

Kit, I am also going to buy a can or two of plastic primer for future use.

 

[Nathan]

If it's just one small spot then something oily probably got on it. Were you eating food while you were working because that would do it. I always wipe off everything with alcohol before painting.

 

[hball55]

If it's just one small spot then something oily probably got on it. Were you eating food while you were working because that would do it. I always wipe off everything with alcohol before painting.

That has to be it . . . it was in the back of my mind as the cause. I was using a paper towel (my version of fine grit sandpaper) to rub down the dried coat prior to spraying a second coat and the paper towel had been used before and I had eaten some potato chips earlier in the evening.

 

[dixontj93060]

...I had eaten some potato chips earlier in the evening.

Yikes!

 

[o1d_dude]

I think we have winner!

 

[hball55]

Sorry, that was a joke. My dentist would cringe if I started eating potato chips again.

However, my handling of the nosecone with my bare hands probably did impart some oils onto the nosecone. Nitrile gloves from now on.

 

[3stoogesrocketry]

When I was 4 I took a pb and j sandwich and pressed it onto my parents wall . Years later when they redid the room , I remember it took several coats of good primer and a few coats of paint to finally cover that one 4 x 4 section of wall. I'm betting you have some release agent stuck on your cone. Clean with soap / water and then denatured alcohol .

Eric

 

[hball55]

Completely stripped the nosecone, cleaned with alcohol and the primer went on fine . . . everywhere.

 

[o1d_dude]

Glad to hear it, Hank.

MY Madcow Squat nose cone was what led me to the plastic primer. Now I use it on all my non-fiberglass nose cones...just in case.

 

[DavieRockets]

Yup, that Rustoleum or Do-it brand plastic primer works great for me. My Madcow Squat nosecone came out looking VERY shiny with rattle can paint and that was over 6 years ago. After lots of flights, not even a scratch through to the plastic. I like to put on two light coats and let it dry for a whole week before putting on coats of sandable primer, then sanding with 320 grit before color coating. Just clean the plastic as mentioned by others.

Found this 2014 link with greater detail on the subject. https://www.rocketryforum.com/showt...t-on-plastic-nose-cones&p=1375778#post1375778

 

[danielsadjadi]

Painting before allowing full time for the paint or primer to dry between coats can result in a wrinkling effect as shown here:



Just a heads up for anyone painting

 

[manixFan]

Both Krylon and Rustoluem recommend paint thinner to clean plastic before painting:

Krylon's instructions:

https://www.krylon.com/how-to/spray-paint-surface-preparation/

And the label from Rustoleum.

https://www.rustoleum.com/~/media/D.../CBG/Specialty/SP_12oz_Paint for Plastic.ashx

For more than you ever wanted to know about painting plastic:

https://www.adhesionbonding.com/2012/03/18/preparing-plastics-for-painting/

I've used the open flame burner (propane torch) after some practice it works well for really shiny plastic. (Learned it from printing on plastic). I tried sanding but that was a disaster - just raised fuzz that was hard to get rid of.

As always, YMMV.


Tony

 

[hball55]

Painting before allowing full time for the paint or primer to dry between coats can result in a wrinkling effect as shown here:

View attachment 284548

Just a heads up for anyone painting

I've been there. I put some water slide decals on my Estes AGM-12D Bullpup and sprayed a clearcoat sealer to hold the decals and the paint bubbled just like that. Cheap little rocket, so I didn't bother to try and fix it. The next day, I just took my finger and pressed the bubbles flat, lol.

 

[o1d_dude]

About a week for the plastic primer to cure does the trick for me, too.

Payience, Grasshopper.

 

[manixFan]

Painting before allowing full time for the paint or primer to dry between coats can result in a wrinkling effect as shown here...

Actually it looks like you waited too long and painted outside the 'repaint' window. Many paints have a limited repaint window that requires you to repaint within a certain period of time, after which you have to wait much longer to allow the paint to fully cure. Other paints have a 'recoat anytime' capability. For example if you follow the link to the Rustoluem label in my prior post, the instructions say to recoat within one hour or after 48 hours. Krylon Colormaster says before 4 hours or after 24.

It's also possible you painted over an incompatible primer. I've never seen that kind of an effect from painting too soon, generally it just runs or sags. What kind of paint is that and over what primer?


Tony