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Three of a Kind

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Mark R. Clark is owner of Professional PBE Systems in Waterloo, Iowa. He’s a popular industry speaker and consultant and is celebrating his 32nd year as a contributing editor to BodyShop Business.

In my 27 years in the industry, I’ve never
seen paint problems more infrequently than I do today. Massive,
critical paint failures are extremely rare in any shop that uses
a single brand of automotive finishes from start to finish. The
few times in the last couple of years that I’ve gone to look at
an entire job that "blew up" on the painter, the shop
was mixing brands of undercoats, catalysts and topcoats.

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Of course, using a single brand doesn’t automatically
mean your paint jobs will be flawless. A lot depends on the painter
and the environment, and a few paint problems still plague us
all when weather and shop conditions change.

From a couple of feet away, three of these
plaguing problems look very similar. To the naked eye, solvent
popping, moisture blisters and fisheyes all look about the same
– like tiny holes in the paint. Since they look so similar, here
are some tips to help you tell them apart and to prevent them
from ruining your paint work.

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Solvent Pop

Under a 30X microscope (which you can buy
at a hobby shop for $10), solvent popping looks like a miniature
volcano. The edges surrounding the hole in the paint film are
peeled back just like the top of a volcano. Like the molten rocks
inside the volcano that burst through the Earth’s crust in a huge
explosion, solvent that’s trapped inside a paint film that has
dried only on the very top layer will violently burst out into
the air.

This bursting happens when the top layer of
the paint film loses solvent and dries before the rest of the
solvent – trapped in the lower portion of the paint film – can
escape. If your solvent speed is just a little too fast, the bulk
of the solvent will escape, leaving just enough trapped solvent
to cause die back. If your solvent speed is way out of whack,
the bulk of the solvent will be trapped inside and popping is
inevitable, leaving little holes in the paint film. Solvent pop
is a more violent form of die back.

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Paint dry speed is dependent on the temperature,
the humidity and the air movement past the vehicle.

  • Hot temperatures cause paint solvents to evaporate quickly;
    cold temperatures cause solvent to linger inside the paint film
    for a long time – just long enough to cause runs and to fingerprint
    the next day.

  • Humidity’s effect on dry times varies with the temperature.
    Hot, dry weather – such as in Arizona – causes the solvent to
    flash off very fast. Cold, damp weather – such as in Iowa – causes
    the solvent to remain inside the paint film.
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  • Air movement past the car has an enormous effect on dry times.
    Just like blowing on her fingernail polish causes your female
    friend’s nails to dry faster, blowing more air past the car will
    rapidly suck out the solvent from the paint film.

    Unless you can control these elements – shop temperature and humidity
    – all year around, you’ll need to change solvent dry speeds to
    suit changing shop conditions. Solvent popping generally happens
    when the weather changes and the painter doesn’t add a slower
    solvent. When in doubt about solvent speed, choose the slowest
    solvent you can use without running the paint off onto the floor.
    The solvent is too slow when it stays sticky long enough to collect
    excess dirt and dust.

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    Though it’s also possible to create solvent popping by applying
    the paint film too thick, the root cause of the solvent pop is
    the same: The top layer of paint dried before the remainder of
    the solvent could evaporate through the many coats of paint film,
    and instead, punched its way out, leaving a hole in the finish.

    Moisture Blisters

    Looking through the 30X battery microscope, you can see the edges
    of moisture blisters aren’t peeled back like those in solvent
    popping. Instead, these holes look like miniature craters with
    smooth, round edges.

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    What causes these miniature craters? Water.

    Water comes in three forms: solid, liquid and vapor. The difference
    in form is the result of temperature changes. Successful paint
    shops have long since done everything in their power to trap moisture
    vapor in compressed-air lines before it reaches the paint job.
    However, on very hot and humid days, many shop moisture traps
    can be overwhelmed.

    The result: The water is sprayed onto the car inside the paint
    film. Once the paint begins to dry, the water droplets rise to
    the top edge of the paint film and are incorporated into it. The
    paint resin then glosses up and hardens while the water droplets
    continue to evaporate, leaving behind empty pits.

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    Note: Clearcoats are particularly susceptible to a moisture-pitting
    problem in hot, humid weather. If the pits are small enough, they
    can often be color sanded out and polished back to a gloss.

    If your shop has moisture running through its air lines, it’s
    also possible to trap such a large amount of water inside the
    paint film that the drops – rather than rising to the top edge
    – are encapsulated inside the paint film. These water blisters
    will bulge up after the paint dries, and when they’re pierced
    with an ice pick, water will run out. If you have this much water
    in your paint line, I’ll bet your air tools are rusted solid,
    too!

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    Final filters that screw onto the spray-gun air inlet are designed
    to trap the last little bit of moisture that slips by the desiccant
    drier or refrigerated air dryer, but they’re not a long-term solution
    to a moisture problem.

    Fisheyes

    These little holes in the paint film are the most difficult of
    the three to diagnose and correct. Unlike solvent popping, which
    is always caused by the top layer of paint drying too fast, and
    moisture blisters, which are usually sprayed onto the car in the
    compressed air, fisheyes can be caused by many different things.

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    The 30X microscope can help you identify fisheyes. Under such
    magnification, it’s possible to see that these imperfections have
    a tiny moat around them. Why? Because the paint film flowed around
    the imperfection much like a river splits around a large rock
    in a riverbed. The contamination that interrupted the paint flow
    can come from many sources.

    Here are some tips to try to identify the cause:

    • When a customer calls with a fisheye problem, the first question
      I ask is whether the fisheyes are on just the flats (hood, top
      or decklid) or if they’re on the sides of the vehicle, too.

    If the contamination is just on the flats and not the sides, my
    best guess is that the contaminant blew or drifted into the booth
    and settled on the car.

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    If the contamination had been in the air line, the paint or the
    spray gun, the entire car would be plagued with fisheyes. Because
    it’s not, it’s likely that something like tire dressing or diesel
    smoke was sucked into the booth after the car was solvent wiped.
    Conscientious cleaning with wax and grease remover is the surest
    solution to prevent fisheyes in this case.

    • If the fisheyes are all over the vehicle, they could have
      come from the air line.

    Worn air-compressor piston rings allow oil to be blown downstream,
    which will definitely cause fisheyes. An oil coalescer is designed
    to trap this oil, which is carried down the air lines on the back
    of water droplets. When the effluent from your moisture trap is
    white, the water has oil in it. Stopping these kinds of fisheyes
    permanently will have to be done at the piston rings.

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    • If the entire car is covered with fisheyes, the spray gun
      could also be the cause.

    If your shop uses a gun washer, it’s possible that the cleaning
    solvent is contaminated with something. In the early days of gun
    washers, we had several dealership body shops whose gun washers
    got contaminated when the mechanics washed out service parts,
    such as a carburetor. The spray guns that were exposed to the
    contamination had to be completely disassembled and cleaned to
    remove the problem.

    • If the fisheyes are on the entire vehicle, another cause could
      be a sophisticated paint sealant/wax.

    These products are often sold by new car dealers and can be very
    difficult to remove when painting is necessary. The test for cleanliness
    is to toss a cup of clean water on the part after you’ve cleaned
    it. If the water sheets off, the part is clean; if the water beads
    up, the part isn’t clean and you must reclean it with something
    that will dissolve the paint sealant.

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    I generally recommend that our customers try their regular solvent-based
    wax and grease remover first. If water still beads up, we have
    them try an alcohol-based wax and grease remover. The trick is
    to find something that will break the bond the sealant has to
    the paint. If neither type of wax and grease remover works, we
    have the painters try a mixture of very hot water and laundry
    detergent. Sometimes the same enzymes in the laundry soap that
    remove your tough stains will also break the sealant’s bond to
    the paint. Once the test cup of water sheets off, wipe the panel
    with regular wax and grease remover to pick up any soap film the
    detergent may have left behind.

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    When the fisheyes in your shop come and go, finding the source
    is a true challenge; it’s actually easier to solve a fisheye problem
    if the shop has them in all the paint work.

    We’ve had our best success when we made charts listing every variable
    for a given paint job, including which painter, which spray gun,
    which air line, what make of car, which undercoats, which solvents,
    what color, what time of day, what day of the week, etc. Although
    no painter wants to play 20 questions every time something needs
    to be painted – it takes way too much time – it’s your only chance
    to find and correct randomly occurring fisheyes.

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    Tending to Tiny Holes

    Simply using a single brand of paint products won’t guarantee
    flawless finishes. You must also take into consideration the painter
    and the shop conditions.

    Hopefully, your shop continuously changes solvent speeds to keep
    in tune with the weather and never has solvent popping in you
    finishes. Likewise, if you install the right equipment to dry
    the compressed air and you maintain it carefully, your chance
    of seeing the tiny moisture holes in your paint work are pretty
    slim. Unfortunately, tiny holes that result from fisheyes are
    hard to prevent.

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    Whatever their cause, don’t let the size of these holes fool you.
    They may be tiny, but their effects on your bottom line can be
    huge.

    Mark Clark, owner of Clark Supply Corporation in Waterloo,
    Iowa, is a contributing editor to BodyShop Business.

    Check it Out

    To the naked eye, solvent popping, moisture blisters and fisheyes
    all look about the same – like tiny holes in the paint. But it’s
    important to tell them apart to cure them.

    • Solvent popping looks like a miniature volcano, with the edges
      surrounding the hole in the paint film peeled back. Solvent popping
      occurs when the top layer of the paint film loses solvent and
      dries before the rest of the solvent – trapped in the lower portion
      of the paint film – can escape. Solvent popping generally happens
      when the weather changes and the painter doesn’t add a slower
      solvent.
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  • Moisture blisters look like miniature craters with smooth,
    round edges and are caused when water is sprayed onto the car
    inside the paint film. Once the paint begins to dry, the water
    droplets rise to the top edge of the paint film and are incorporated
    in it. The paint resin then glosses up and hardens while the water
    droplets continue to evaporate, leaving behind empty pits.

  • Fisheyes – which have tiny moats around them – are the most
    difficult to diagnose and correct because they can be caused by
    many different things. If the fisheyes are just on the flats of
    the vehicle, the contaminant probably blew or drifted into the
    booth and settled on the car; if the contamination had been in
    the air line, the paint or the spray gun, the entire car would
    be plagued with fisheyes.

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