Painting Problem

[zeke1312]

I'm not sure if this is the correct forum to use for the following question. I apologize if so. I've been building a Nike Ajax rocket and I'm at the painting stage. I started painting last fall, applying 4 primer coats spaced 3 or more days apart, then 3 coats of white semi-gloss painting spraying each coat evenly as possible.

Yesterday, I applied a 4th coat of white paint and noticed an area where the fin in question attached to the tube body began to wrinkle(orange peel?). Elmers white glue was used to attach all body parts.

After drying, I sanded the area in question which ran somewhat parallel to the body down to the primer and painted again with the white finish coat. It began to wrinkle again but a larger area now appeared. I am using Kilz primer and Krylon finish.

I then sanded down to the bare balsa wood and have started to apply primer. I plan to apply another primer coat in a couple of days.

Any idea what is happening here? What's the best way to feather the bare wood to the painted area or should I sand the whole side of the fin and start over?

The rest of the rocket body paint looks good.

[Doug Sams]

I am using Kilz primer and Krylon finish.I'm worried about compatibility between these two. Kilz is an oil-based primer (You did use the oil-based and not the water-based, right?) and you're covering it with a hot enamel (ie, almost a lacquer). I would think you're better off using an automotive spray primer (ie, something hot like the Krylon).

That said, I think you're also being way too careful. You don't need to wait "3 or more days" between primer coats. With Kilz - double check the label - but I think you can space thin coats about an hour apart. With automotive primers, 20 minutes works well.

Likewise, for your top coats, you can apply a color in one multi-coat session. Start out with a vary light coat - called a tack coat. It doesn't need to cover 100% opaquely - just get some paint on the bird. Wait about 5 minutes with Krylon (10 mins for say RustOleum) then apply another coat, this time a bit heavier. If everything looks good, you're done. Else, wait a few more minutes and paint again. Then quit. Unless you're adding a different color, there's no need to wait a few days between coats - a few minutes is all you need. If you are adding a different color, then waiting a week or so is necessary to ensure the 1st color is fully cured (and thus tolerant of the solvents in the 2nd color).

Yesterday, I applied a 4th coat of white paint and noticed an area where the fin in question attached to the tube body began to wrinkle(orange peel?). Elmers white glue was used to attach all body parts.How long did you wait between the 3rd and 4th coats? It sounds like your 4th coat softened the 3rd and caused it to wrinkle (BTW, no, that's not orange peel). If you put the white on last fall, it should surely have been cured by now, but sometimes $tuff happens.


HTH.

Doug

[zeke1312]

Hi Doug:

I am using Kilz Craft Coat primer that contains Toluene, Acetone and Xylene. The finish paint is Krylon satin that contains Xylene, Acetates. I assume these ingredients are compatible?

I applied the 3rd coat of Krylon last fall.

If the 2 paints were not compatible, should not the whole rocket exhibit the same paint problem?

[ghrocketman]

Kilz Craft Coat is compatible with Krylon.
I have found no compatibility issues with Kilz "regular" with Krylon, Rust-Oleum, Dutch Boy Fresh-Look, WalMart ColorPlace, or Testors Enamel.
Just don't try topcoating it with Pactra Aero Gloss Dope.....what a mess !
If using Dope as a topcoat, the best primer is PactraPrep, secondly Lacquer Auto Primer.
I finish a lot of rockets with AeroGloss as I have cases of NOS AeroGloss dope in most colors.

[Doug Sams]

I am using Kilz Craft Coat primer that contains Toluene, Acetone and Xylene. The finish paint is Krylon satin that contains Xylene, Acetates. I assume these ingredients are compatible?Yeah, they sound compatible. I don't think I've noticed the Kilz Craft before, but it definitely sounds up to the task.

I applied the 3rd coat of Krylon last fall.The 3rd coat should have been plenty cured.

If the 2 paints were not compatible, should not the whole rocket exhibit the same paint problem?At this point, I'd be inclined to choose option D, $tuff happens.

If it's happening in the fin root where the glue was, then there may be an adhesion issue. Hypothesis: The top coat is pulling lightly on the underlying coats, and that's enough to pull it off the glue. Was the glue exposed? Or did the paint only lift off the primer, leaving the primer intact and unwrinkled?

If that's the case, could be couple things: Did you wipe it down good with a tack rag before spraying? Could you have gotten some sort of contamination on the surface which would prevent paint adhesion in that spot? (Normally, you would get fish eyes if that's the case.)

FWIW, I'm not convinced anything (paint wise) adheres that well to Elmers, white or yellow, but I haven't been able to conclude that with certainty. Occasionally, I'll get some bubbling in the fin roots under the paint. This usually occurs after heating during flight, but sometimes a couple hours in the hot car causes it, too.

Not sure exactly what it's due to. If may be the FNF lifting in the root off the glue due to poor adhesion, or it may be due to me inadequately working the FNF in place during application. And it may not be the FNF at all. It could be the paint/primer lifting off the FNF, likely due to un-dried moisture still in the FNF when the primer was applied. (Sometimes I guess 24 hours isn't long enough for thick fillets of FNF. :)

Anyway, at this point, I think you need to let the paint cure for a few days before trying to fix it.

Doug

[Doug Sams]

Just don't try topcoating it with Pactra Aero Gloss Dope.....what a mess !Yeah, I discovered that in round-about way recently. I knew better than to put the clear dope on non-dope paints, but didn't anticipate this. I had some of the red body filler used for scratch filling. Normally, I use FNF for that sort of thing, but if I'm in a hurry to paint something and see some spots needing filling at the last minute, I'll use the red stuff. In thin coats, you can sand it in as little as 20 minutes, prime, then be shooting paint in a half hour.

Well, my tube was kinda old and stiff, so I thinned the stuff a bit with dope thinner, then brushed it on. Clever, right? Not! About 10 minutes later, everything in that area had lifted off the nosecone all the way down to bare wood. The primer and underlying FNF had both been softened. #$%*!

Lesson: dont' use dope thinner to thin fillers (or primers).

Doug

[Solomoriah]

I painted a Thunderbee using Miracal primer (the cheap stuff), followed by an overall coat of Kilz Craftcoat yellow. When it was good and hard I taped it up and painted it with Wal-Mart ColorPlace black. The finish came out beautiful.

Then I clearcoated it with Krylon. Bubble city. I use the Krylon clear coat all the time with good results. I sanded it off, repainted it the same way again, and used ColorPlace clearcoat. Bubble city again. Said numerous bad words, then sanded off and repainted a third time. Finished with a rag and Future.

I've also had problems with bubbling at the fin root when painting over epoxy fillets (I love 30 minute epoxy fillets). One rocket got sanded and repainted along two fin root sides out of six three times before it straightened up. I have no idea why it didn't bubble anywhere else on the rocket.

Painting rockets is an art, for sure.

[ScaleNut]

i have experienced small but very noticable linear cracks when using regular krylon over Kilz
more than once infact

[zeke1312]

OK, I sanded down the area in question to the balsa. Re-primed w/kilz 3x then Krylon satin 3x. Looks good. I don't plan on using a clearcoat, just leaving it satin. Now to the decals.

[BatPlane]

An observation:

If you spray balsa with, Krylon for example, then hit it with a hair dryer, it'll bubble up ridiculously.

If you warm up a can of Testor's enamel, then spray your rocket, it will bubble up all over the place.

I really believe the temperature of the balsa and the stuff you're spraying on it have to be about the same. I'm thinking they should both be on the cool side, actually.

I have no scientific basis for this....just personal experience.

[zeke1312]

Just to make a point in my case the paint actually wrinkled instead of bubbled. The Kilz primer looked good after being sprayed on. Maybe it was residual white glue under the Kilz that when the Krylon was applied, caused the problem. Next time I'll use the same manf paint for the primer and finish.