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HDU primer

Discussion in 'Newbie Forum' started by Jimmy Burds, Nov 23, 2019.

  1. Jimmy Burds

    Jimmy Burds New Member

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    Oct 24, 2019
    Commerce City, CO
    What are the best primers for high density urethane?
     
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  2. tbullo

    tbullo Superunknown

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    You will get lots of opinions on this. I like using FSC 88 WB on my HDU(Signfoam) signs.
     
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  3. Sindex Printing

    Sindex Printing Member

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    Sparks
    We use Fsc 88 WB
     
  4. Z SIGNS

    Z SIGNS Very Active Member

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    I've tried many hdu primers.I 've found ronan stik-tite.Had trouble with the latex primers not adhering well.
     
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  5. TimToad

    TimToad Very Active Member

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    We use Insl-X brand STIX urethane primer for all of our HDU work. This stuff sticks well to nearly any surface and on the can, there is a photo of it being applied to ceramic tile.

    First coat, super thin, second coat thicker, and third tinted and mixed partially with our background finish color. That last coat seems to really saturate into whatever few open cells still remain after the first two coats.
     
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  6. kcollinsdesign

    kcollinsdesign Active Member

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    Normal, Illinois
    HDU is not porous, it is a closed cell urethane foam. Machining it opens up the cells at the surface, creating a "toothy" texture. I use a high-build latex primer (Coastal enterprises recommends FSC 88 WB, SignFoam peddles a similar product). Probably not the best solution if you are on a production line and need to spray, but works excellently with brush (recommended) or roller. The paint is heavy bodied, and fills up the texture. It can be painted on in one, fairly heavy coat, then sanded with 600 grit sandpaper to get a perfectly smooth surface. These specialty primers are easy to sand; don't fall into the trap of buying an inexpensive high-build latex primer from the paint store - it will be difficult to sand!

    I know the big boys use an automotive grade high build primer that is designed for spray application, then coat with acrylic polyurethane. You'll need to talk to them about their preferences. But if you are doing less than a dozen or so HDU signs a week, the brush on primer is cheap, fast, and easy!
     
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  7. signbrad

    signbrad Member

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    Jun 15, 2014
    Kansas City
    When Coastal Enterprises first made FSC88 it was solvent based. You could wet sand it with a mix of water and mineral spirits. The wet sanding created a slick slurry of the FSC88 that filled in all the pinholes. If I did this twice on a piece the primered surface was like glass. It would then accept bulletin enamels or automotive paint (acrylic enamel at the time). The finish you could produce was flawless. When I ventured into marbleizing, I could achieve incredible realism.

    FSC88 was discontinued and replaced with FSC88WB, which is water-based. I was disappointed. I was never able to quickly achieve a glasslike marble look with water-based primers. Marbleizing became too much trouble and not labor-friendly....till I started using Matthews products.

    Matthews Polyester Primer/Surfacer 6001 is a catalyzed primer engineered for HDU. Nothing I have found compares to this product. It dries and sands quickly. I can spray successive coats and, as with the original solvent-based FSC88, achieve a glass finish in a short time. A small amount of the mix can even be used as a filler that you can apply with a knife to nicks and gouges. Just mix it and let it begin to set up. It works like autobody filler. In fact, those of you who have done autobody work will recognized its smell immediately...Bondo. It is liquid Bondo.

    You can roll it or brush it, but spraying is super fast. I use a huge 2.0 tip and clean the gun within a short time. I have sprayed successive coats without cleaning in between, but I don't wait too long before cleaning. If it gets away from you you may need to buy a rebuild kit. When I use this product I always do a partial break down of the gun at the end of the day, I pull both inner and outer nozzles and the needle and brush and clean all orifices and lube everything thoroughly. Of course, many of you do this anyway at the end of the day. At the Matthews paint school, the instructor said, "if you are not spending 15 minutes at the end of the day cleaning the gun, you are not getting it clean enough."

    The Matthews 2-day paint seminar will teach you to use the Polyester Primer, among other products. They had us roll it with weenie rollers at the school, but spraying is better. If you can ever attend one of these schools it is really beneficial. I am hoping to go to my third one when it comes back to Kansas City this spring. I learn more each time I go and I will gladly burn a vacation day to attend again.

    Brad in Kansas City


    https://www.matthewspaint.com/Produ...Low-VOC/Polyester-Primer-Surfacer-6001SP.aspx
     
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  8. Zendavor Signs

    Zendavor Signs Member

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    Peoria, IL
    We have used this primer before, and it does work great. The problem we have is the topcoats. What do you paint on top of this? It has to be oil based, correct? We have found that unless we wait 4-5 days, 1 shot paints react to the primer.
     
  9. signbrad

    signbrad Member

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    We use Matthews Polyurethane topcoats on the Polyester primer. We use Matthews topcoats for pretty much everything except wood posts and other raw wood components.
    It's good to know that One Shot does not react well to this primer. I wonder if latex has a problem with it, too. Does One Shot try to fish eye or crawl? Or something else?

    Obviously, if Matthews topcoats are the only finish coats that work well with the Polyester primer then it is not the best choice for an HDU primer for many of us. Waiting four or five days to topcoat is not practical for anybody. I may ask about this at the next Matthews school. Many paint reps say to use primers and topcoats from the same company.
    .................

    You are a Peorian? I came up in the trade in the Peoria area. I even joined the IBPAT (now the IUPAT), Local 157. I was a one-man shop but by having a painters union card the business reps left me alone when I lettered walls and windows downtown. Most of the Peoria guys I knew are passed away except some of those who were young when I was there in the 70s.
     
  10. Chet carter

    Chet carter New Member

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    Apr 23, 2018
    USA
    Brad, I’ve enjoyed reading your expert advice about priming HDU. I have just started using the 6001sp from Matthews also and problem I am having is I get little pin holes or porosity in the primer that reveals itself once I go to sand before topcoat.

    I’ll prime with 3-4 thick coats of the 6001sp, allow to dry and when I go to sand it reveals the little pinholes. Almost like the primer is mimicking the pinholes in the HDU if that’s makes any sense. What do you think could be causing this?

    I’m using an HVLP set at about 15psi, 2.0 tip.
     
  11. signbrad

    signbrad Member

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    Chet,

    I usually don’t rely on a single spraying of the 6001 primer. Even if I am spraying it heavily I let it dry and sand it down and spray again. Using 400 or 320 grit paper on a DA sander it should sand well if it’s dry. It should powder nicely and not ball up. I have Applied as many as three and four separate spray coats with sanding in between. This is when I want it to be very smooth or when I am going to marbleize as the final finish. It may seem time-consuming but the primer dries fast. And you can do other things between coats.

    If you are OK with a textured finish then simply use one of the latex primers, a couple of coats. This is what most people seem to do who do not mind an orange peel finish.

    We are a high production shop but I force myself to use multiple coats of 6001 with dry time and sanding in between. I do not like the textured look that latex paint so often yields.

    Try applying your heavy coats after sanding your initial coats of 6001. See if that does not make a difference.

    Also, I have experimented with spraying coat after coat of 6001, till it is almost puddling. I have not noticed it to ever be a problem. It is not like a topcoat which surface dries causing problems when the paint is applied to heavy. Remember that this stuff is like liquid Bondo. Bondo is often applied in thicknesses measured in several millimeters rather than just a few mils (thousandths).

    One other point I might add about Matthews paints in general, including the 6001 primer—the addition of catalyst should be precise. Do not add extra. It will not dry properly and will ball up when you sand. Additional reducer can be added to a mix, but not additional catalyst.

    I would recommend to anyone using Matthews paints to attend their free two-day school. Ask questions while you are there. You will learn a lot in a short amount of time. And they will feed you Friday night.

    Brad in Kansas City
     
  12. Chet carter

    Chet carter New Member

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    Apr 23, 2018
    USA
    Brad,
    Your thorough response is greatly appreciated. I had not previously sanded between coats of primer (or at least after my initial coats) so I will definitely give this a shot. I am like you an prefer a very smooth finish and not textured like you get with latex.

    As for the class thanks for the recommendation, I had already actually called about this and was planning on taking it. Glad to hear some good feedback on it. Thank you.
     
  13. Zendavor Signs

    Zendavor Signs Member

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    Mar 3, 2011
    Peoria, IL
    Sorry, Brad, I did not see your response earlier. The One Shot paint just never dried. It stayed tacky for well over a week. It was clearly some kind of reaction. We have stuck with latex primers lately. We really liked the finish of the polyester primer though.

    Yes, born and raised in Peoria, which is where my shop is now. I'm not familiar with the union you noted, but I don't believe I had been born yet.
     
  14. Chet carter

    Chet carter New Member

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    Apr 23, 2018
    USA
    brad, curious if you’ve ever tried to thin the 6001 with anything?
     
  15. signbrad

    signbrad Member

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    Kansas City
    Chet,
    No, I haven't.
    I do use a bigger spray tip, though, compared to the size for other Matthews products. We have a primer gun with a 2.0 tip that works well.
    Brad
     
  16. visual800

    visual800 Very Active Member

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    Aug 4, 2010
    montgomery, alabama
    Ive always primed with latex and had great results, of course I spayed it and made sure the surface of the HDU wall completely clean. We also paint all HDI with latext As far as you guys using ONE SHOT for anything, throw all that away, ONE SHOT is crap and should not be used on anything.

    Is there a reason you feel the need to use urethanes on hdu?
     
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