• If You Are Having Trouble Logging In with Your Old Username and Password, Please use this Forgot Your Password link to get re-established.
  • Hey! Be sure to login or register!

Stewarts Systems Ekocrylic bubbling.

wdoubleday

Registered User
Hi Folks,

just finishing my engine installation and the last task is to paint my cowling doors. I’ve been using the Stewarts system on my project. The main color is sport yellow. The picture below is the first time this has happened to me, but have read previous accounts of a similar situation where all looks good, you’ve achieved the gloss wet look on your final spray, but after an overnight cure, the surface looks like 50 grit sandpaper. I have been using their Ekocrylic on all composite and metal parts, as directed. No issues to date as I’ve been sticking to their parameters for shooting their paint.
Just wanted to pass along what I probably did wrong. In shooting my last part, this cowling door, I let my shop get a little too warm up to 85 F. I also shot too much paint on this part. The top coat started to set before the underlying paint was still off-gassing water vapor which caused the surface to form these microbubbles. This is the one downside of waterbourne paints where the flashpoint of water is higher than lower boiling point solvents that evaporate more quickly. Need to allow sufficient time between coats, and minimize the amount of paint you spray. The other issue is selecting yellow which is the toughest color to get color saturation on your parts. Small part is easy to remedy but always extra work - sand down to primer and reshoot. When properly applied, the Stewarts paint seems to work well, but time will tell.

cheers,
Wendel

0496BEA0-1D66-4D57-82BE-53FEE1549C2A.jpeg
 

Attachments

  • 0496BEA0-1D66-4D57-82BE-53FEE1549C2A.jpeg
    0496BEA0-1D66-4D57-82BE-53FEE1549C2A.jpeg
    173.7 KB · Views: 295
I think they are on to something, but I have neither the skill, patience, nor time to fool with that finicky top coat. I watched my buddy struggle with it on his Cub for the last year and a half. Acceptable, but my 1981 acrylic enamel Cub is still shinier and smoother.

i think Stewart needs to add an easier top coat to the STC - say, butyrate, or Poly Tone, or maybe Aerothane.
 
The key to shooting on the top coat is patience .... my biggest nemesis! Fog coats should be tacky but not any transfer should happen when you touch your knuckle to the paint. Give it time between coats, pot time is 3-5 hours. Small pieces are more difficult to shoot because of the wait time to tack up. It's ok to get your first three fog coats on than let it sit 24 hours. After that, go over it with red scotchbrite or 320 sandpaper than remove all the dust and fog on one more coat before the wet coat. This allows all outgassing to occur before that last tack coat and wet coat. If you have any solvent pops (the little bubbles) in the first fog coats it's because the coats were wet (still transfer to knuckle) before next coat and likely too heavy. As long as it's sticky you can shoot on the next coat.

Regarding a different top coat for the STC, the paints mentioned all require solvents. One of our main objectives is to provide a quality product that is safe to apply. With all the solvent based systems extreme care must be used when handling and using the paints. The need for outside air is critical with a solvent based system but not with ours. Another big plus is providing a product that has no hazmat issues; safer to apply and a lot easier to ship.

Let me know if you have any more questions. My next seminar is again up in Alaska; end of February.

Marty57
 
The key that we found when developing this system is to throw your watch out the window. The paint is ready to accept the next coat when it's ready. You can't time it and get it right. I've had it ready in 10 minutes....but I've waited an hour as well...and more often. The beauty of this topcoat is the generous time limit once it's ready to accept the next coat. You have lots of time! As long as it's sticky, fire away! I usually get to the point of final coat and go eat.
This paint loves heat, so letting your shop get warm isn't an issue! Airflow and temperature affect waterbornes a bunch in the speed that they dry. Remember, you're evaporating water, not a traditional solvent.
It's not hard...just different. I'll take the longevity and health benefits any time!
John
 
Do you shoot white, then yellow on top, or trying yellow with no white under it?

I’ve been using Stits epoxy primer white for all aluminum and fiberglass parts with no issues up to this point. I checked with Stewarts who replied that should not be an issue if you allow several weeks for full cure of primer.
 
So does Stewarts....and it's more flexible, and not so hazardous. Kinda like landing a taildragger....not that tough but different.
 
Not that tough? My buddy struggled for a year! He bought every single thing recommended by Stewart. He built a spray booth with intake and exhaust filters. He installed lights. He studied under a master. He followed different kinds of advice. My latest Poly Tone sprayed in the driveway looks better, and I am anything but a spray gun expert - just a dirtbag Binks 18.
His Cub will look ok, but it will never have that "wet look".
 
Not THAT difficult, Bob - easy once you get the hang of it. Just can't let old habits dominate. Like Marty sez, gotta be patient, and enjoy repetitive cups of tea between coats. :lol:
 
Yep, not that difficult. I've taught men, women, kids.... the WORST to teach were men...especially if they'd painted solvent based paint before. I was one of them.... old habits die hard.
John
 
I have not yet seen a properly finished Stewart cover job. I have seen three that were more or less satisfactory. They tell me there is an impeccable Starduster at SDM. Anxious to see it.
 
There's a local PA-18 done in Stewarts that looks similar to the Randolph dope. Still very nice and parked outdoors currently at -30F. There are also others that didn't tun out as well and have various spots of silver repairs. Like cakes must be the baker.

There are also several Stits Polytone jobs that are prone to cracking and oxidation. I've had two.

Gary
 
My Randolph dope is wet-sanded and compounded to a reasonable shine. Not as good as Randthane or other urethanes, but shiny. If I could legally put butyrate dope on top of Ekofill, that would be the answer for me. I have had spectacular results with minor repairs like that. And we have done spot repairs with Stewart Cub Yellow that look great, but it does not take talent to "gloss out" a 2x2 area.
 
And yeah, we have a Poly Tone Cub that doesn't look all that great. Some day I will re-tape it and shoot it with butyrate. But we fly it too much to worry much about appearance.
 
Mine does not like rain , after 2 or 3 days of rain ,bubbling all over top surface, let an inspection hole in water for a few days and see for yourself. NEVER AGAIN !

Leave it inside when it rain and your good. :evil:
 
Mine does not like rain , after 2 or 3 days of rain ,bubbling all over top surface, let an inspection hole in water for a few days and see for yourself. NEVER AGAIN !

Leave it inside when it rain and your good. :evil:


Frenchy, I’m curious, did you use diluted ekobond to seal your weave before applying the ekofill coats or was it done using the older method of brush in ekofill followed by spray applications of ekofill? I have heard of adhesion issues there.

Before shooting, I made test strips and soaked one in H2O and one in car gas for over a month. When I removed the strips from their containers, they still looked as perfect as the day I applied the paint. Not a single bubble or perceivable issue. The finish was also very glossy. Hope it lasts for a while...so far so good. Plane is hangared, but has sat in the rain plenty.
 
It is really important that the fabric weave be sealed with a three to one Ekobond glue to water (by weight) mixture before EkoFill is applied. In the past, we showed just EkoFill applied on bare fabric, dampened with water first. That worked if fabric was wet when EkoFill was applied. Often, the fabric dried before EkoFill went on and it did not bond to the fabric weave. The issue than was when water entered the inside of a wing (drain holes and condensation) delamination between the EkoFill and fabric was possible. If you have a bubble in the paint and you see bare fabric, this is the issue. By sealing the weave with EkoBond followed by EkoFill and than the top coat, the EkoFill is encapsulated between two layers that are impervious to water. We introduced the use of EkoBond for filling of the weave back in 2017 and have removed the option of EkoFill on bare fabric from the manual in the Rev. 4, July 2019. If you see bare fabric under a bubble it's because of bonding issues of the EkoFill; If you see gray EkoFill under the bubble and only the top coat lifted, that is another issue altogether and is most likely caused by contamination. Some Auto gas with ethanol will attack the bond of the top coat but that depends on the additives used in the regional blend of the autogas. California gas causes lots of issues, Ohio gas none at all; no telling what is added to auto gas in your area. If you filled the weave with EkoBond and have any delamination, it is the EkoFill delaminating. I found this in a sample I placed in CA auto gas with ethanol, the EkoFill delaminated. Auto gas here is horrible stuff and can not be purchased without the 10% mix. 100LL caused no issues and I have a sample now in 100LL for two years with no effect at all. I hope this sheds some light on how best to prepare the fabric to avoid buggles.

As first stated here, the biggest issue patience. No matter how you prep the fabric, solvent pops will happen if you don't give each coat time to fully tack up with no transfer to your knuckle at all.

Marty
 
Frenchy, I’m curious, did you use diluted ekobond to seal your weave before applying the ekofill coats or was it done using the older method of brush in ekofill followed by spray applications of ekofill? I have heard of adhesion issues there.

Before shooting, I made test strips and soaked one in H2O and one in car gas for over a month. When I removed the strips from their containers, they still looked as perfect as the day I applied the paint. Not a single bubble or perceivable issue. The finish was also very glossy. Hope it lasts for a while...so far so good. Plane is hangared, but has sat in the rain plenty.

Older method, first 6 months in a hangar, it was great. Put the plane on floats and leave it outside for summer. little rian, no problems, but after a week of wet conditions. bubblings shows up. i`m not the only one here in Quebec, a guy painted a Bushcaddy(aluminium plane) same bubbling problem. Personnally i will never use it again, even if you give it to me for free. To much work to take that chance. The only thing i love about steward is the glue. Like i said, don't take any chance and leave your plane inside when wet.
I will try to take some pictures of my paint, it is now hangared for winter.


Good luck
 
Last edited:
And each time they CHANGE methods, paint, or such. The track record clock needs to be reset to ZERO!! Can’t make claims of xx years when you change the process.... I’m sticking with dope or stitts, unless customer wants to gamble by their choice... and this is one of two processes I will not do even then...


Sent from my iPhone using SuperCub.Org
 
Actually.... using the diluted glue to seal the weave of the fabric is how we developed the system and did it in the 90's. When Stewarts took it over was when they changed that, so actually it's back to original. Hasn't been an issue with that system.
John
 
Quick question: I know that distilled water is a good idea in the finicky finish coat, but what would tap water do to that glue?
 
Ok...understanding HOW they work will help you. I always tell everyone to look for 4 letters... "CYAN"...that means cyanide in the mix. If you understand how it attacks your centeral nervous system, you can work with it. Are waterborne polyurethanes completely harmless? Absolutely NOT. But the percentage of isocyanide is very low in the catalyst, and it is attracted to moisture. Our body is about 70% moisture, so in a solventborne paint, the isocyanide is looking for moisture, and it follows the path of least resistance...your soft tissues...eyes, nose, internal, armpits, throat, etc. With a waterborne polyurethane, you already have plenty of moisture in the mix, so it's happier in there. Does that mean you don't need to protect yourself? Absolutely NOT! So when do you think the most dangerous point in the painting process is??? It's certainly not spraying!!! The most dangerous point is when you're adding catalyst to the paint. At that time, the isocyanide is a "free radical" and "hunting". I don't know how many times I've seen people don all the proper gear in the booth, only to ignore all that when they're mixing their paint..... think about it.
The reason I wound up finding all this out is that I was young, dumb and bullet proof. I had to experience a very bad reaction before I started to believe that I needed all that "safety stuff"... I wound up in the hospital and I went through a few days that I wouldn't wish on anyone. This was the main reason I wound up being one of the developers of the system. If I hadn't found it, I was pretty much done with painting. If you see me in my booth, I'm always covered, and setup to contend with the hazard. I'm so sensitive to the stuff that I can "taste" it even with Stewarts anymore.
So no, even waterborne's aren't totally safe...no paint is... not even polytone. It all boils down to protecting yourself and understanding what you're working with.
 
Quick question: I know that distilled water is a good idea in the finicky finish coat, but what would tap water do to that glue?

It totally depends on what crap is in your tap water....some places it'd probably be fine...in other places, it could be not so fine.
 
I used Stewart's on our Cub. Did the ecobond on the fabric just like the manual says. Did tests with av gas and ethanol free premium. No effect with av gas. Premium separated the paint between the ecobond and ecofill. Wouldn't be a problem if I only used av gas. I run premium. For that reason I won't be using their paint or ecofill again. Auto fuel doesn't effect our other airplane finished with Stewart's in '06.
 
Back
Top