Re-spraying bike

Matthewnewton89
Matthewnewton89 Posts: 5
edited July 2015 in Workshop
I have a slight annoying issue with spray painting my mountain bike.

I decided few days ago to spray my bike frame silver. Reading up on various website they all say to sand the paint work after re-spraying it with 1200 grit sandpaper before applying the laqure making sure that the frame is wet when sanding. The issue I have is that when I do that the sandpaper leaves back marks all over. I'm not sure what I'm doing wrong all I can think of is that the paint hasn't fully dried out.

Comments

  • dgunthor
    dgunthor Posts: 644
    are you using wet and dry sandpaper?
  • Yes, I am using wet-dry sandpaper.
  • reds99
    reds99 Posts: 46
    Use sand paper, not wet and dry, very lightly abrade the paint surface. this is to provide a key(?) for the lacquer to adhere to.
  • lesfirth
    lesfirth Posts: 1,382
    Wet or dry abrasive paper should be used wet. Use it very lightly you are only removing any slight imperfections in the colour coat ,anything else should have been sorted before you applied the colour. If you have marks that will not wash off it does sound as though you colour coat has not dried properly. If that's the case put your frame somewhere warm for a couple of days and try again. What sort of paint have you used?
  • I used car spray paint.
  • Fingerling
    Fingerling Posts: 29
    Same process as spraying car parts. Depending on how thick you applied the paint it might not have dried. Solver isn't z great colour to do first time round. All you are doing is keying the paint before lacquer. You can use a green kitchen scrubber to achieve the same result.

    Another way is to add lacquer before the silver has fully dried. I would key the frame again, do a light coat of silver then a couple coats of lacquer.
  • I've just been thinking really since it's a aluminium frame which looks silver/chrome anyway is it worth bothering. Would it be better to try sand to a good finish and then apply some lacquer to it or even just polish and buffer it ?
  • Elfed
    Elfed Posts: 459
    I have a slight annoying issue with spray painting my mountain bike.

    I decided few days ago to spray my bike frame silver. Reading up on various website they all say to sand the paint work after re-spraying it with 1200 grit sandpaper before applying the laquer making sure that the frame is wet when sanding. The issue I have is that when I do that the sandpaper leaves back marks all over. I'm not sure what I'm doing wrong all I can think of is that the paint hasn't fully dried out.

    Wet and Dry paper needs to be used wet, dipped in a bucket of water to keep it lubricated.
    The black marks's probably the paint being too soft and clogging the paper.
  • reds99
    reds99 Posts: 46
    If you have used car paint and it isn't dry, no ifs or buts you didn't mix the paint correctly.
    So as suggested put another coat on, then when that coat is tacky spray the lacquer. Best way to test for tacky is to place a piece of cardboard, next to bike so its an extension of the bike, with masking tape applied and use this to see when its tacky. Saves you touching the bike.
    BUT make sure the bike is clean and slightly keyed, scotch brite or as said a kitchen scourer can do this, make sure the coat is applied nice and wet, so slow your arm down as more than likely that coat will not gloss up as well as when you applied the first coat.
  • desweller
    desweller Posts: 5,175
    If you have used car paint and it isn't dry, no ifs or buts you didn't mix the paint correctly.
    So as suggested put another coat on, then when that coat is tacky spray the lacquer. Best way to test for tacky is to place a piece of cardboard, next to bike so its an extension of the bike, with masking tape applied and use this to see when its tacky. Saves you touching the bike.
    BUT make sure the bike is clean and slightly keyed, scotch brite or as said a kitchen scourer can do this, make sure the coat is applied nice and wet, so slow your arm down as more than likely that coat will not gloss up as well as when you applied the first coat.

    Really? The reason I query this is because I had a few problems with getting my paintwork to go hard when I resprayed mine a couple of years ago, and I think it's because I did not leave enough time for each layer to cure properly...
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  • reds99
    reds99 Posts: 46
    Most paints are 3 pack paints(paint, activator, thinner). Most paints are mixed 2:1:1. If you don't use thinners or not enough all classic signs of whats being described. Same with the activator. Activator is not the same as a thinner.
    Previously paints were 2 pack(paint, activator) again wrong mix, paint just doesn't dry and form its coat/shell.
    Not leaving enough time between coats won't stop properly fixed paint from drying, you could end up with a terrible looking finish or solvent popping in the surface of the paint. Thats the thinner still releasing air as it dries, or tacks off, so all it can do is pop into the next coat.
    Remember all these car paints etc are designed to be sprayed in optimum conditions, dried in optimum conditions, so unless you spray for a living or had any training, picking up a spray gun will be much trial and a lot of error.
  • lesfirth
    lesfirth Posts: 1,382
    I think we need some more detail from Mathew of the type of car paint being used and how it is being sprayed.
  • desweller
    desweller Posts: 5,175
    I'm gonna put my money on rattlecans...that's what I used.
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  • reds99
    reds99 Posts: 46
    If you have used car paint and it isn't dry, no ifs or buts you didn't mix the paint correctly.
    So as suggested put another coat on, then when that coat is tacky spray the lacquer. Best way to test for tacky is to place a piece of cardboard, next to bike so its an extension of the bike, with masking tape applied and use this to see when its tacky. Saves you touching the bike.
    BUT make sure the bike is clean and slightly keyed, scotch brite or as said a kitchen scourer can do this, make sure the coat is applied nice and wet, so slow your arm down as more than likely that coat will not gloss up as well as when you applied the first coat.

    Really? The reason I query this is because I had a few problems with getting my paintwork to go hard when I resprayed mine a couple of years ago, and I think it's because I did not leave enough time for each layer to cure properly...

    So you come on querying advise, and you used a rattle can. Unbelieveable! Wheres the mixing of paint involved there? You shake the tin as advised on the tin and more.
  • desweller
    desweller Posts: 5,175
    If you have used car paint and it isn't dry, no ifs or buts you didn't mix the paint correctly.
    So as suggested put another coat on, then when that coat is tacky spray the lacquer. Best way to test for tacky is to place a piece of cardboard, next to bike so its an extension of the bike, with masking tape applied and use this to see when its tacky. Saves you touching the bike.
    BUT make sure the bike is clean and slightly keyed, scotch brite or as said a kitchen scourer can do this, make sure the coat is applied nice and wet, so slow your arm down as more than likely that coat will not gloss up as well as when you applied the first coat.

    Really? The reason I query this is because I had a few problems with getting my paintwork to go hard when I resprayed mine a couple of years ago, and I think it's because I did not leave enough time for each layer to cure properly...

    So you come on querying advise, and you used a rattle can. Unbelieveable! Wheres the mixing of paint involved there? You shake the tin as advised on the tin and more.

    Wasn't querying the mixing, was querying the tacky. It was a genuine question, wasn't having a go by any means! No compressor, and just the one (cheap) frame to spray - wasn't going to drop any dough on extra tools.
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    On Strava.{/url}
  • dj58
    dj58 Posts: 2,221
    [quote DesWeller

    "Wasn't querying the mixing, was querying the tacky. It was a genuine question, wasn't having a go by any means! No compressor, and just the one (cheap) frame to spray - wasn't going to drop any dough on extra tools."[/quote]

    That is know as a wet-on-wet finish, where the lacquer coat is applied after the colour coat solvent has flashed off, but before the colour coat has completely dried, i.e. remains tacky, this aids the adhesion of the lacquer to the colour coat, as opposed to letting the colour coat dry and then keying and lacquering.
  • Unless you used a million of them the paint layer from rattlecans will be so thin you will very very quickly sand through it, even with 1200 grit.