Paint chalking

  1. KimB

    KimB Member

    Messages:
    1,865
    Location:
    UK
    Hi guys, so I painted the bi-fold gate posts this weekend. For some reason on of the posts especially has what I think is called paint chalking. Some areas it’s perfect and others bits it’s got powder like finish to it? Any idea?
    0767BBF0-27A5-41FF-B30F-87601B4C738F.jpeg
    Can be seen clearly below?
    F47D251C-C88A-4456-9F0A-AAF895D264B2.jpeg
     
  2. Fazerruss

    Fazerruss Member

    Messages:
    2,536
    West Yorkshire
    I've had this happen when painting in cold conditions. For me it tends to only happen with cellulose based paints and is obviously more visible on black rather that lighter colours.
     
    andy28 and KimB like this.
  3. Shedendman

    Shedendman Member

    Messages:
    4,016
    east sussex
    What paint did you use?
     
  4. Brad93

    Brad93 M J B Engineering

    Messages:
    7,388
    Location:
    Essex
    It’s too cold to paint at the minute Kim.
     
    andy28, KimB and brightspark like this.
  5. brightspark

    brightspark Member

    Messages:
    28,882
    Location:
    yarm
    called bloom in cold damp conditions
     
    Windy Miller, Hopefuldave and Brad93 like this.
  6. Shedendman

    Shedendman Member

    Messages:
    4,016
    east sussex
  7. arther dailey Member

    Messages:
    3,724
    Location:
    Southampton England
    if you are going to re paint get a hot air gun and warm the metal first, obviously not to hot to blister paint but enought to dry the metal and leave touch warm, infra red heater also good for this , paint , then apply gentle heat again. a faff but stops damp affecting paint.
     
    Ian James, Parm, Hopefuldave and 3 others like this.
  8. KimB

    KimB Member

    Messages:
    1,865
    Location:
    UK
    Thanks for all the advice guys. Maybe that’s why the bigger one did it and the smaller didn’t. I had a heater in there but the thick post is twice as thick and twice the size so obviously requires more heat to get to a decent temp.
     
  9. KimB

    KimB Member

    Messages:
    1,865
    Location:
    UK
    Any idea in the temp the steel should be to paint? Like I say I had a heater in there over night but it still went like that
     
  10. Shedendman

    Shedendman Member

    Messages:
    4,016
    east sussex
    What does it say on the tin,should have depending what paint it is at what temps are ideal to use in
    I take it,it was primed/undercoated 1st,or was it a one coat does all jobby?
     
  11. KimB

    KimB Member

    Messages:
    1,865
    Location:
    UK
    No I primed it yesterday with grey zinc primer. I ordered it from paint4trade or something like that. I asked their advice before ordering and that’s what they sent but I’ll have to get a pic because I can’t remember what it’s called.
     
    Ashley Burton and Shedendman like this.
  12. Shedendman

    Shedendman Member

    Messages:
    4,016
    east sussex
  13. Brad93

    Brad93 M J B Engineering

    Messages:
    7,388
    Location:
    Essex
    Minimum 10 degrees, that’s air temp, I’d personally want 15 degrees so the steel is at least 10.
     
    andy28, KimB and eLuSiVeMiTe like this.
  14. KimB

    KimB Member

    Messages:
    1,865
    Location:
    UK
  15. Dcal

    Dcal Forum Supporter

    Messages:
    1,819
    Location:
    Antrim Northern Ireland
    Theirs no need to guess, just get a technical data sheet for the paints they supplied. (They will be available from the manufacturer's website.)
    It will tell you the environmental conditions required for application and drying.

    Reasonable application temperature is always better but some paints can be applied below freezing (most are two pack and have a winter or fast hardener for the application)
    The big problem is water or most probably in your case condensation and that depends on temperature and relative humidity.
    Relative humidity isn't that easy to measure without proper kit but if it feels damp in the garage or cold surfaces are damp it's below the dew point and you shouldn't paint.
    Usually manufacturers recommend 3 to 5 degrees above the dew point for painting.

    Having said that if you had a heater in the garage and it was warmer inside than outside I'm surprised you had a problem.
     
    Parm likes this.
  16. KimB

    KimB Member

    Messages:
    1,865
    Location:
    UK
    E50860B7-AAF0-4154-B0D0-49A1D5700190.jpeg 082F19BE-4936-4075-831D-FBAE1D072EA0.jpeg C525F57A-5C4A-4F7E-9F54-64938AC7DB7B.jpeg
     
  17. sako243

    sako243 Member

    Messages:
    905
    Location:
    My mansion in Wales
    Did you have the heater on for a long period before starting painting? 8mm steel is going to take a long time to warm up to ambient. As it'll likely be cooler there may well be condensation starting to form.

    If you're going to reapply it it might be worth using a blow torch or aiming the heater directly at the steel to get it up to / over temperature and then letting it cool back down to the warmer ambient.

    I know you like keeping the house tidy but it's there any chance of bringing it inside to do the painting? It'll be warmer and dryer than the garage (hopefully).
     
  18. Ashley Burton

    Ashley Burton Member

    Messages:
    3,486
    Location:
    Northamptonhire
    Yeah I don't think you've got the weather for painting steel that thick. It's going to take some heating to get it up to a good temperature to paint if I'm honest
     
  19. KimB

    KimB Member

    Messages:
    1,865
    Location:
    UK
    I might see if I can get a gas space heater. Maybe be able to do it then. I can’t get it in my house and I’m spraying it so defo won’t be doing it in the house haha.
     
    sako243 and Ashley Burton like this.
  20. Ashley Burton

    Ashley Burton Member

    Messages:
    3,486
    Location:
    Northamptonhire
    Only problem with gas is that it creates condensation

    Just an idea, But could you bring it inside to get it upto room temperature, Spray it in the garage & bring it back inside to dry?
     
    Ian James likes this.
Advertisements