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Thread: What am I doing wrong - Spraying Exterior Latex

  1. #1
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    What am I doing wrong - Spraying Exterior Latex

    I'm quite experienced shooting pre-cat lacquer which is my go to finish, but I have an exterior piece that I am having issues with.

    The paint is Sherwin-Williams Exterior Super Paint Acrylic Latex.

    HVLP gun is Fuji T-70
    Tip size 1.8
    Turbine - Fuji Q4 Platinum

    I would think my tip size is appropriate for the paint, and the 4-stage turbine should provide enough power.

    This is what the first coat of the finish looks like:
    Exterior Latex 1.jpg

    I did add about 50 ml of Floetrol to one quart cup in my 3M PPS system. I didn't check the viscosity (I'm so used to using the same Pre-Cat Lacquer, that I haven't done that in a while.)

    So what adjustments do I need to make? This is spraying splotchy, and certainly doesn't level out like lacquer.
    - Its not that Im so smart, its just that I stay with problems longer. Albert Einstein
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  2. #2
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    The turbine might be heating it up enough that it sets before it has time to flow out.

  3. #3
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    Alan, you need to measure the viscosity. I suspect it will be really high; like 500 seconds (if you can wait that long) through a #4 Ford cup. You'll likely need to get it down to less than 1/2 of that in order for it to spray well. If you have to add more than 10% water to do that I would look for a different product.

    I once sprayed SW's Emerald Exterior Acrylic latex and could not get it flow out no matter what I did. If the Super Paint you are using is anything like that you probably won't be successful either unless you use an airless sprayer. I switched to Emerald Urethane Trim Enamel and it was a world of difference; sprays and flows out beautifully. It's a completely different product and much better suited to HVLP guns. I still had to thin it 10% for good atomization but after that it was great. I'm not suggesting that it's the right product for your needs, only that some products are better suited to airless sprayers while others can be successfully sprayed with a broader range of spray gun types. Good luck.

    John

  4. #4
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    John:

    I'll have to measure it tomorrow. Thanks for the detailed response.

    Can I add both Floetrol and up to 10% water to thin it, or is it a total amount of dilution limit?

    The Floetrol TDS states that you can add up to 8oz of Floetrol to a quart of latex paint (which seems like a huge amount). I added 50 ml, which is a drop in the bucket (about 1.7 oz) compared to that.
    - Its not that Im so smart, its just that I stay with problems longer. Albert Einstein
    - Welcome to Florida. Where the old folks visit their parents

  5. #5
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    Alan, because of how waterborne finishes work, when you exceed the suggested 10% thinning limit (and to me that means both water and extender/conditioner like Flotrol) you start to spread the paint molecules out to the point that you start to have coverage issues and potentially a less durable finish as the actual finish cures/coeleces. Water is not the solvent for waterborne finishes...it's just the carrier. So I agree with John...you may not be able to spray that finish with your rig and an airless might be a better choice to get it done.
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  6. #6
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    I only use an airless for that type of work and paint. (or a roller and brush)

  7. #7
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    I really have no good experience with Floetrol, Alan, sorry. I've only used it a couple of times when brushing/rolling paint in hot weather and it didn't seem to do anything. When I started spraying I looked for another product. I found GF's Extender, which I use for clearcoats, and BM's Extender which I use for paints. Both work very well. With the BM product, which I buy at my local BM retail store, I think they say you can use up to 6%.

    I try to follow the maximum thinning limits for the product I'm using. With some waterborne products the PDS says you can add up to 20%, others 10%. Look and see what SW's says for the product you are using but truthfully, if it says 10% I wouldn't hesitate to use a few more percent if that makes the difference between success or failure, and sometimes a few percent makes a huge difference in viscosity. In any case, if another go at it doesn't work it's probably time to change products or spray gun.

    John

  8. #8
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    Benjamin Moores "extender" will thin it down enough, but you will be exceeding the recommendations.

    (no title)

    I will paste the data sheet, B.M. Extender is a great product. I have good results using it with many brands of paint.
    Last edited by Maurice Mcmurry; 01-13-2022 at 7:41 AM. Reason: 8 oz per gal.

  9. #9
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    It's a one-off project, so doesn't make sense to buy airless for it.

    I think it did level off somewhat, but I would never accept that initial spray on a typical project I do.

    OK. Off to the workshop to measure the viscosity, and try to dilute it somewhat. I'll measure before and after.
    I may try 4 oz of Floetrol in a quart of paint. 12.5% Will probably try that first. Perhaps add some water to that too. Seems way too dilute.

    SW website for the paint says reduction not required. Not helpful at all regarding this.

    On Phelps Refinishing site, their recommendations with the Fuji guns to spray latex are:
    1) Use the air cap set 1.8mm.
    2) Thin the paint upwards of 20% with water.
    3) Use additives if necessary.
    4) Add the 6-ft whip hose to reduce air temperature through the gun.
    5) Hold the gun no more than 8″ (20cm) away.
    6) Apply a full, wet coat.
    7.) Turn the fluid adjusting screw to limit the paint to a finer spray.

    He specifically states that Floetrol is an additive, not a thinner, though the caption for Floetrol calls it one of the popular thinners.


    What do people use for tip size to spray latex? It looks like the tips for my T70 gun go up to 2.5, but I never considered buying any that large.
    Last edited by Alan Lightstone; 01-13-2022 at 10:45 AM.
    - Its not that Im so smart, its just that I stay with problems longer. Albert Einstein
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  10. #10
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    OK. As John thought, the viscosity through a Ford #4 cap for the undiluted paint was 296 seconds (yup, hard to wait that long).

    With 50 ml of Floetrol/quart, the viscosity went down to 219 seconds.
    With 150 ml of Floetrol/qt the viscosity went down to 63 seconds.

    So I used the 150ml/qt and sprayed. Yup, the sprayed coating on the wood was very thin, but didn't run at all on vertical surfaces. I did turn the fluid adjusting screw far tighter than I usually wood, per Phelp's suggestion, but it also seemed like way too light a coat.

    Certainly not as easy as spraying pre-cat lacquer, or shellac, but I'll get through it.

    I'm assuming that 63 seconds is still crazy thick?
    - Its not that Im so smart, its just that I stay with problems longer. Albert Einstein
    - Welcome to Florida. Where the old folks visit their parents

  11. #11
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    63 seconds is likely far lower than what your gun is capable of spraying well. I would limit the Floetrol to 50 ml/quart (5%) and use water to get the viscosity down to around 100 seconds. I'll bet that will spray well for you. Of course, the coating will be thinner than spraying it neat from the can, and you may have to spray an extra coat, but that's the compromise you have to accept when your equipment and product aren't really compatible.

    John

  12. #12
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    I plan to get a Graco Ultra hand held for small projects. The regular paint pump is too much trouble and takes most of a gallon just to fill the pump and lines. A pressure pot helps with thick paint but still does not do well with latex. I paint a lot of doors on homes. With the Benjamin Moore Extender, good paint, and careful use of a roller followed by a brush, I can get results that look like oil paint or a sprayer was used.

  13. #13
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    Use a smaller, short line for an airless, and there is not that much paint in the rig. I push most of it back in the can with water. I think my small line is 1/4x15 feet. It's good for small jobs. To me the regular airless is less trouble to clean than the small ones.

  14. #14
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    Speaking of which, the biggest issue/annoyance with spraying this is clean up of the gun. So easy with lacquer, such a royal paid with the latex. Any hints for doing this. Dried latex or drying latex all throughout the gun, even though I've been cleaning it immediately after spraying. Not used to having to clean it multiple times a day.

    Really should have just brushed this.
    - Its not that Im so smart, its just that I stay with problems longer. Albert Einstein
    - Welcome to Florida. Where the old folks visit their parents

  15. #15
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    I only use waterborne finishes and that very occasionally occasionally includes "house paint" type products. I use hot water right from the tap in the kitchen sink and have never had an issue with cleaning my gun(s). Should something actually be dried, a solvent cleaner can be used, but I try to avoid that by cleaning immediately once the job is done.
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