Thinning Bottom Paint

Discussion in 'Materials' started by Chuck Losness, Sep 29, 2011.

  1. Chuck Losness
    Joined: Apr 2008
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    Chuck Losness Senior Member

    While talking with some of the other boat owners in the yard where I am hauled out the topic came up as to whether or not you should thin bottom paint. Some said no problem and others said you should not thin bottom paint. With the hot temperatures here bottom paint gets thick pretty quick and some people thin it to make it go on easier. So what does the forum think. To thin or not to thin?
     
  2. michael pierzga
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    michael pierzga Senior Member

    Dont do it. When the solvent becomes entrapped as the outer skin dries , you very well achieve the one billion bubble antifoul job. Bottom paint should be applied from the can and only thinned for special applications. Paint you bottom in the shade.
     
  3. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Michael is correct, don't thin the paint, but out gassing as he suggests isn't the reason. Simply put it's dilution of the paint and there's no reason the thin a rolled and/or brushed anti foul. If it's sprayed, this is a different animal, but I've never known an owner that sprayed bottom paint. Work patches small enough to keep a wet edge. Lastly, alkyds and acrylics out gas long after a surface skin has formed Michael. The vehicle may take up to a month to fully out gas, depending on formulation.
     
  4. tunnels

    tunnels Previous Member

    Fore and against thinning in general
    Have you ever noticed when this question pops up there lots squabbling .
    Not all thinners are born equal ! Some are fast evaporating some are slow to eveaporate and some never !! Me i like fast evatorating but its all dependant on the size of the job !! Small that is a 10 minute wonder and over and done with quickly fast is good !! Fast evaporating !,90% has evaporated before the paint even gets to the surface of the job .
    Bigger jobs where you need to overlap your spray wet on wet you need slower thinners so the top coats etch into each other ! In some situations slow thinners is the only way to get the job done without the overspray showing all over the job . Air flow around the job and the temparture all have a lot to do with what happens and no two days are ever the same !!
    Lots depends on the spray equipment you are using and nozzels size on the gun , I prefer using pressure pots and using small amount of thinner to thin only to get a smooth finish , the joys of a pressure pot is you can wind the pot pressure to get the volumn and flow just the thinners to get the spray to flatter out smooth . Air less sprays in some situartions need to be thinned slightly alway depending on what kind of finish you exspect . Again weather conditions have a lot to do with painting . So to thin or not to thin ??? :(:confused::p:D:p;)
     
  5. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Again, we're spraying anti fouling now Tunnels? How many owners would even attempt this? Let along now how to cut a product to improve flow rates and maintain a wet edge from a gun?

    Of course when spraying, you do need to cut most of the time, typically just enough to remove stipple. If it's hot outside a flow modifier is a much better choice, such as Penatrol or similar. In most cases, particularly with the newest anti foul formulations, you should call the tech line and see what their tropical reducer or wetting agents are and general cutting percentages.

    My point is, most owners, will roll, brush or roll and tip bottom paint, mostly because they don't have the equipment, can't use the equipment or are just plain scared of the damn paint itself. I can't blame them really, I've grown an extra thumb from all the years of working with anti foul and other "marine" concoctions. It does make wiping my butt more entertaining.

    If applying bottom paint by hand, then a flow modifier (Penatrol) is the best choice.
     
  6. tunnels

    tunnels Previous Member

    Anti fouling we always sprayed !!:)Power boats and yachts .
    On racing yachts used to then when hard 400 grit wet sand paper to give it a slip finish for racing !!. :p
    Airless spray equipment they use all the time for big jobs and pressure pots that hold the complete one gallon tin for smaller boats .
    Also did teflon coatings as well !.:eek:
    Worst was the copper based with all the poisens and crap in it . Used a electric mechanical stirer on the top of the pot
    Always sprayed after hours when every one had gone home and only two of us there .
    Rolling left a slightly roughened stippled effect that guys werent to happy about so was easyer and got a better job spraying .:D
     
  7. michael pierzga
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    michael pierzga Senior Member

    Dont thin antifoul for spray or roll application. Use a short nap roller and two thin coats , Day one coat and Day two coat or an airless spraygun fitted with the proper tip, shooting carefully mixed and filtered antifoul in one application . Apply the paint to the recommended paint film thickness.

    Always read the product data sheets and apllicators guide. note "Thinning not recomended"

    http://www.yachtpaint.com/MPYACMDatasheets/Micron_66__ eng A4 Y 20110620.pdf
     
  8. tunnels

    tunnels Previous Member

    Anti fouling we always sprayed !!:)Power boats and yachts .
    On racing yachts used to then when hard 400 grit wet sand paper to give it a slip finish for racing !!. :p
    Airless spray equipment they use all the time for big jobs and pressure pots that hold the complete one gallon tin for smaller boats .
    Also did teflon coatings as well !.:eek:
    Worst was the copper based with all the poisens and crap in it . Used a electric mechanical stirer on the top of the pot
    Always sprayed after working hours when every one had gone home and just two of us there .
     
  9. michael pierzga
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    michael pierzga Senior Member

    Airless spray application only for antifoul. For racing yachts the resulting airless antifoul finish , applied by a pro painter, will be 90 percent perfect and ready to be polished back after the paint has cured. I have not witnessed a conventional spray antifoul job in twenty years. Beside killing the paint applicator and incurring huge plastic on off labor costs, the effective antifoul film thickness will not be to manufacture specs.

    If the original poster is after a smooth rolled on antifoul finish then use a short nap roller and apply one thin coat...then waite until the antifoul has fully cured..24 hrs... then apply the second coat. Always work in the shade. A very nice finish can be achieved.

    To make any paint flow on a substate the surface must be sanded. For anti foul jobs the best, fastest, cleanest way to sand the antifoul is wet. Use a long stick, say 1.5 meter, fitted with a swivel head DRY WALL hand sander, loaded with 80 grit wet or dry, and use plenty of water. The work goes very fast and the workman stays out of the toxic mess.
     
  10. whitepointer23

    whitepointer23 Previous Member

    i am having a bit of chuckle about this. i bought a can of antifoul today and on the label it recomends thinning with 3% 304 thinners if using a roller in hot windy conditions. it is the copper free stuff for aluminium though.
     
  11. michael pierzga
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    michael pierzga Senior Member

    No need to chuckle... just read the product application guide. " THINNING IS NOT RECOMENDED"

    http://ppgamercoatau.ppgpmc.com/docs/ABC PDS.pdf

    And naturally dont paint in the bright sunshine on a windy day
     
  12. whitepointer23

    whitepointer23 Previous Member

    if my scanner worked i would send my product application guide which states thinning with 3% thinners. it is from the same company . its ppg ecofleet alloy. tin and copper free
     
  13. michael pierzga
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    michael pierzga Senior Member

    No need ..I sent you the product data sheet...the paint should be applied straight from the can. any antifoul Ive ever used stated the same thing.

    If you are painting your own boat youre welcome to experiment.

    The boats Im involved with carry a "Guarantee" for antifoul performance . the price for the typical haul antifoul cycle is 10,000 plus euro. This 60 to 80 liter...4,000 euro paint purchase arrives to the yard complete with a technical representative from the paint company. The tech rep Never allows thinner, the surface prep is inspected and film thickness of the finished product as well as the batch numbers of the paint supplied are logged.
     
  14. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Slight cutting is often required, particularly in spray applications, just to get it through the gun, but manually applied bottom paint doesn't need this. It's not an out gassing issue and film thickness can be bulked up with sufficient coats. It's a dilution issue. Knocking the "edge" off the paint, with a few percent cut isn't significant, but most folks that "thin" paint, do so in much larger ratios, upwards of 20% and 30% which dramatically reduces the film's effectiveness as an anti foul and it's ability to stick to the surface.
     

  15. whitepointer23

    whitepointer23 Previous Member

    i understand what you say, but it is on the label and in my application guide. i have never thinned antifoul because i live in a cool area anway. why would ppg state the use of thinners and then not recomend them.
     
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