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Spraying issue

  • Denis Murphy
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22 Dec 2020 17:37 #23890 by Denis Murphy
Spraying issue was created by Denis Murphy
Hi all. I have repaired a cowl that took a bashing. Brought it back to life with epoxy filler etc Sanded it down to a smooth finish and primed it.rubbed back and sprayed 3 coats of RC spray tin paint. I was really pleased with the finish(for me). I thought I'd give it a coat of clear lacquer to give it a nice shine. I applied what I thought was clear, RC Gloss. The first piece I sprayed came out as a watered down milk colour instead of clear. I followed the instructions etc. Anyway I only gave a very thin coat to about 30% of the surface.My question is do I a). Rub the affected area with wet and dry and respray this piece or the whole cowl again ? or b) attack the affected area with something like t-cut and not respray at all? c) something else?

I know if I use option a, I might not get as good a finish as the first time. Any advice appreciated. Also for future reference what is a good clear lacquer that people would recommend?

Cheers

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23 Dec 2020 08:48 - 23 Dec 2020 08:49 #23897 by Jon Tappin
Replied by Jon Tappin on topic Spraying issue
Hi Denis, I feel your pain, I'm spraying at the moment and there always seems to be some kind of issue that requires rework :(

You could try Tcut or similar, but if the milky finish remains you'll have to rub down and go again I'm afraid. As to why it went milky I'm not sure, I have never used that particular product before, but back in the days when I used cellulose based paints this could happen when painting in humid air, it's called 'blooming'

If you want to use something else instead on the 2nd attempt, it's really important to make sure the materials are compatible, so paint a scrap piece with the base colour and spray the clear onto that to make sure there's no reaction, before you do the actual part.

I have used Halfords 'petrol proof lacquer' before with decent results on acrylic paint, this can go slightly milky if applied too thick, but dries clear. But the best single part clear I've used in a can is the stuff that Rainbow Paints in Ferndown sell.

Hope that helps
Last edit: 23 Dec 2020 08:49 by Jon Tappin.

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23 Dec 2020 09:04 #23899 by Denis Murphy
Replied by Denis Murphy on topic Spraying issue
Thank Jon. I'll try those options this morning in that order. Cheers.

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23 Dec 2020 09:10 #23900 by Jon Tappin
Replied by Jon Tappin on topic Spraying issue
I forgot to say, to speed up the polishing process, you can rub down with very fine wet and dry, 2000-2500 grit, then polish, this will cut through the upper layer faster and will still polish to a gloss afterwards. They sell this in Halfords also.

Good luck!

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23 Dec 2020 10:50 #23901 by Brian Jackson
Replied by Brian Jackson on topic Spraying issue
"Milky" finish is sometimes caused by cold damp conditions during spraying. You might try warming the surface with a hot air gun, this works with solvent based lacquers. Don't hold the gun too close or it'll blister the surface.

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23 Dec 2020 11:41 - 23 Dec 2020 11:43 #23903 by Phillip Ford
Replied by Phillip Ford on topic Spraying issue
Denis, if this RC Colours paint which I believe is an enamel it should have come out in glossy on it's own and needs a week to harden through before recoating. I suspect as others have said that conditions were too cold and /or damp. Been down this road many times.

My grp Chipmunk cowls had to be stripped right down again and wet n dry was no good so resorted to Acetone. Takes the enamel straight off but is messy as you have wipe with old rags quickly. But at least your down to the plastic again. I also found that RC Colours is not foolproof against glow fuel residue. Petrol may leave a tide mark. I did find though that Aerokote fuel proofer gloss works quite well as a lacquer coat.

My electric and petrol planes are painted with good ole Halfords car paints finished with acrylic lacquer. Note though their petrol version needs to put on after the base coats have had time to harden so not a rush job. Motabitz Ferndown can match paint colours to covering film.
Last edit: 23 Dec 2020 11:43 by Phillip Ford.

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24 Dec 2020 09:39 #23909 by Denis Murphy
Replied by Denis Murphy on topic Spraying issue
Well as I thought, in trying to t-cut my cowl, it has made it even worse! I'll get the wet and dry out and cut it back to the primer and respray the whole thing. This time I won't spray on the clear lacquer! Even if I don't get the nice finish I had before applying the gloss coat, it will be far better than it is now. Most expensive cowl repair ever.LOL

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