Tinting gelcoat for a re-color

Discussion in 'Materials' started by Dan H, Jun 10, 2009.

  1. Dan H
    Joined: Jun 2009
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    Dan H Junior Member

    Greetings everyone, first time poster here.
    I have taken the torturous path of changing the color of my white sailboat to dark blue and am trying to do it with gelcoat. Yes I am crazy.
    I am having trouble tinting the neutral gelcoat enough to get it to hide the original color.
    I have tinted the gelcoat with 4oz. pigment per gallon. I am using Duratec 50/50 and I think that is thinning out the color too much.
    I've done this with white gelcoat and have had no problems, this is the first time using neutral gelcoat.
    What am I doing wrong here?
    Can I increase the pigment until it covers or is going over 4oz of pigment per gallon a sin?
    How much pigment can I safely use per gallon of gelcoat?
    Thanks Much
    Dan
     
  2. Wynand N
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    Wynand N Retired Steelboatbuilder

    Amount of tint varies with different brand names. The NCS products we use calls for 5% pigment to clear gelcoat. Cray Valley products on the other hand calls for 5 - 10% on various pigments they supply to us.

    When tinting white gelcoat, be careful for over pigmentation. For example, to make grey gelcoat, rather mix some black pigment to clear gelcoat, and add that mix to the white gelcoat until desired shade of grey is achieved. This way you will use much less pigment than trying to shade white to grey with black pigment only and you will not end up with over pigmentation that will bring about a lot of other gremlins.
    Same applies with other colors from white.
     
  3. pescaloco
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    pescaloco Senior Member

    dura tech

    Hey Dan,

    I have had similar results even with color matching whites using Duratec

    The trick is to get your color how you want it with little or no Duratec then have enough base material left to mix it 50/50 on you final spray. In other words you would say laydown your color 1-2 cotes then add your Duratec.

    You could do say 25% Duratec on 2nd or 3rd cote then 50/50 on 3rd or 4th cote. There is too much opacity to use on the first coverage.

    I like gelcote my self but I am sure most would recommend to paint as it is less work
     
  4. Dan H
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    Dan H Junior Member

    I found out that pigments are mixed with regards to the type of gelcoat and the type of pigment. One size does not fit all as Wynand said.
    I found out that the pigment and gelcoat that I'm using is to be pigmented at 1/2lb / gallon and I only used 1/4lb / gallon. The supplier straitened me out and is sending more pigment. She did the math and has me on the right track.
    Thanks guys for your help.
    On a side note, I am one to follow the directions and never stray. Some day I'll take a walk on the wild side and add too much thinner or not follow the directions for once, and see what happens. I seem to let the instructions drive me and not allow common sense take over.
    Point being, I was so upset last night, I added more pigment to see what would happen. Guess what? The result was much better, but not great. I was uncomfortable doing that, but it turns out it was the right thing to do. Some day I'll listen to common sense and something will work out.
    Thanks for lending an ear,
    Dan
     
  5. mark775

    mark775 Guest

    Thanks, good thread. I've probably over-tinted a bunch in my life and didn't know it. I guess I have some to learn here.
     
  6. Dan H
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    Dan H Junior Member

    I have since learned that using the correct amount of pigment did not result in even cover either.
    However, on the transom, I sanded it half way through with 220 grit and sprayed more over it. The transom came out great. Full hide.
    In talking with people about this, one guy talked about using the finish color as a primer. I've been thinking about that all along.
    When I sanded my hull originally, the white was sanded down to the secondary color in several spots getting the hull fair. The secondary color being red. After spraying the dark blue, the red spots can still be seen through the top coat, despite spraying double the amount of gelcoat, with the correct amount of pigment.
    This tells me I should have used a primer coat. I should have sprayed black or grey first, then the dark blue. I should have known better.
    So now I will begin sanding the entire hull to 220 dry, and try again. This will be the primer coat.
    This time I'm using someone else’s gelcoat and pigment. I am also going to add black to the blue to see if I can increase the opacity. I’ll keep you posted.
    Wish me luck.
    Dan
     
  7. Wynand N
    Joined: Oct 2004
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    Wynand N Retired Steelboatbuilder

    Dan, even with female molding we have the same problem with gelcoat not covering completely (although it look solid when applying) and end up with dull or dark spots in the colour.
    And this is the very reason I always apply two coats of gelcoat - a primer run so to speak and when that gets tacky, we lay down a second coat followed by the glass layup and the results always excellent.

    Good luck with your project:cool:
     
  8. ondarvr
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    ondarvr Senior Member

    Each color can have a different level of hide, even colors that are very close to each other can be much different.

    One problem can be the Duratec clear, it can reduce the viscosity, plus reduce the hide dramatically, so getting complete hide over any surface may be difficult. This is another area where adding "stuff" to resins or gel coat that appears to help, can actually create problems. If the raw materials used in Duratec were of value in gel coat, they would be in the formula to start with.

    Pigment levels in gel coat range from around 5% to 20%, so adding 50% Duratec will cut whatever the amount is in half. If we were able to formulate gel coat that worked well with 50% less pigment we would, pigments are very expensive.

    Adding Duratec will reduce the water and weather resistance of the gel coat, so the reduced labor in sanding the surface due to less orange peel comes at a cost.
     
  9. Dan H
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    Dan H Junior Member

    ondarvr,
    I'm beginning to learn that the hard way. I always thought that thinning the gelcoat with Duratec was thinning the pigments also, obviously. I tried to get a hold of Duratec tech department to ask them about this but they did not return my call.
    Using very little Duratec when spraying the outside of the boat is most likely the best thing to do. I'm only using it for shine and the cure the gelcoat. I don’t believe for a second that I won't have to sand and polish just because I'm using Duratec.
    The problem isn't that it isn’t hiding the base color with one or two coats, I have 7 coats in some areas. Full double wet coats! The last coats were not thinned 50/50 with Duratec but a little less. All I could do was remove the Duratec from the surface when the gelcoat settled in the can. Really surprising.
    I've talked to a gelcoat manufacturer today about testing the opacity while adding pigments.
    My problem is that I always feel, "The next coat will cover it." Some of the coats were left tacky for hours before spraying the next coat. Still doesn't hide. So I'm certainly doing something wrong.
    I am going to test the gelcoat between two pieces of glass for opacity and cure and continue to add pigments until I achieve opacity and the resin still cures. If I get the resin too rich with pigments I can add neutral gelcoat to get it back.
    This is probably why people don't spray gelcoat on the outside of boats.
     

  10. Dan H
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    Dan H Junior Member

    As a test I took 1oz strait Duratec and added a bunch of pigment, catalized it at 2% and let it sit.
    It kicked hard as a rock. It took a few days but it did get hard. So It seems pigmenting Duratec is not a sin after all. I have more experimenting to do.
    So when I pignemnt the gelcaot I'm wondering if I should treat the Duratec just like gelcoat? Hmmmm. me wonders....
     
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