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How to varnish/seal plastic planter

Didn't know where to post this so just trying here. Sorry if it's in the wrong place.

I primed some plastic planters with primer spray paint from the car section in Halfords. I then painted them with a couple of layers of copper acrylic paint. 

What can I seal it with to ensure it's waterproof for outside use? I am not sure the acrylic paint won't wash off eventually if left like that. I have looked for varnish in the hardware shops - the varnish I found all said 'exterior' on it, so I thought it might be okay but they all seem to be for covering woodwork. Is there another varnish type I can use? I don't really want a spray, I want to put it on with a brush.

Thanks in advance.  

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  • hogweedhogweed Central ScotlandPosts: 3,992

    I would go for a clear exterior varnish. And give it a good few coats. Unless you can get your hands on some clear spray (know you said brush) acrylic stuff out of Halfords.

    'Optimism is the faith that leads to achievement' - Helen Keller
  • raisingirlraisingirl East Devon, on the Edge of Exmoor.Posts: 3,905

    Or have a look for boat varnish suitable for metalwork

    “This isn't life in the fast lane, it's life in the oncoming traffic.”
    ― Terry Pratchett
  • wakeshinewakeshine Posts: 963

    Thanks both. Raisingirl yeah I saw some yacht varnish but that seemed to be the same as exterior wood varnish but stronger. Hogweed I read the smallprint on the exterior varnish pots and it said don't use on plastic so I didn't get it. I thought about the spray but I couldn't seem to get the knack of even spraying when I used the primer.

  • Kitty 2Kitty 2 ManchesterPosts: 5,150

    I've used both, a car "touch up" spray can of paint and exterior gloss paint to rejuvenate old plastic pots. The spray was easier to apply but the gloss paint (for exterior wood/metal) lasted longer. I was applying the colour directly to the pots. 

    I would make sure your copper acrylic paint is set rock hard before you try a top coat of varnish and do a test patch to watch for streaks. If it's ok, do a thin covering for a first coat, let it set hard and then follow up with a couple more. 

    I was painting mine from tatty terracotta effect to black and just bunged it on and hoped for the best, but can appreciate that you want a smooth finish to your copper paint. Hope you find a solution to your problem wakeshine image

  • wakeshinewakeshine Posts: 963

    Hi Kitty2 - thank you very much for this advice. I didn't think exterior gloss paint would go straight onto plastic! Always thought everything had to always be primed but obvously not. I am just so crap at spraying spray paint on evenly. With the primer it was terrible job - drips all over the pot even though it was spray. Could not get an even finish. It didn't matter too much as it was a white pot and a white primer, so when it came to putting the copper on, the uneven surface can't really be noticed and it looks a bit more natural. I'm also planning to paint some patterns on in black before varnishing.

    Do you think this woodwork and yacht varnishes are adequate then? I wonder why it says on the tin not to use on plastic? Somewhere else I read mix PVA glue with water but I have no idea of the quantities or if this is as good as varnish!

  • Kitty 2Kitty 2 ManchesterPosts: 5,150

    I think your spray paint might have been drippy if you were holding the can too close to the pot when you sprayed, or sprayed to thickly. I did mine on a tarmac path so it didn't matter if I  got paint on it and did wide sweeping strokes with the can. The car paint only lasted two seasons before it started flaking though. 

    I did wonder about suggesting PVA as a sealer, only because I was worried about a solvent based varnish dissolving the copper acrilyic and causing streaks. I don't understand the chemical makeups of paints and how they interact. 

    I do know that exterior gloss for wood/metal works on plastic. If you don't get a difinitive answer from elsewhere on the forum I'd try hogweeds suggestion of an exterior gloss varnish, just do a test patch first.

  • wakeshinewakeshine Posts: 963

    Thanks Kitty2, really appreciate your thoughts on this. Still haven't decied what to do!

  • hogweedhogweed Central ScotlandPosts: 3,992

    I know this is a bit off the wall but you get transparent sealer in a spray can to seal plastic water pipes. Spray again though. 

    'Optimism is the faith that leads to achievement' - Helen Keller
  • wakeshinewakeshine Posts: 963

    Thanks Hogweed. It's not off the wall, it's a good suggestion. I wish I was better with spray paint. I don't understand how grafitti artists do it - such control with the can and beautiful works of art. I just could not get an even finish and it dripped everywhere too. Luckily I was painting over it anyway but for varnish I need something I can paint on with a brush.

  • ObelixxObelixx Vendée, Western FrancePosts: 22,168

    You have to do loads of very fine coats so the paint and varnish levels don't build up and start to drip.  Shake the can really well, hold it about 9 inches away from the surface and go lightly.   Practise first to build up confidence and expertise.

    You usually can't mix oil based products with oil based surfaces as they tend to dissolve each other which is why some paints and varnishes are not good for plastic surfaces.   If you do use an acrylic varnish use 3 coats max as more than that builds up and gives a milky finish.

    "We don't stop playing because we grow old; we grow old because we stop playing." - George Bernard Shaw
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