Spraying Latex Paint

Can latex paint be sprayed with a siphon type cup gun? If so how is it thinned
Thanks
Joe
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In accordance with the directions on the paint can.
-- Regards, Doug Miller (alphageek-at-milmac-dot-com)
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hi joe,
i just (yesterday) sprayed thick latex with my HVLP (turbinaire) - used a 2MM needle and a #3 cap, and cranked the air all the way up. atomized nicely and came out better than i expected. no thinning. paint was top-of-the-line benjamin moore i believe.
if you are going to thin, try flotrol. as previously mentioned, read the label on the can - manufacturers tend to consider this issue.
do a lot of testing.
good luck,
--- dz
Joe wrote:

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Joe,
Here is something I posted sometime back about my experience with spraying latex. I didn't use a siphon cup, however, I think it would make it slightly more difficult to spray. All you can do is try it out. Please post what you find out. Hope this helps.
--------------------------------------------------------------------------- I just finished spraying a bunch of passage doors this weekend. A very long weekend.
I have a Graco, 4-stage turbine HVLP with a 2 quart remote pot. Since latex is thick, I figured I needed a big tip to get the necessary flow, so I dropped $90 for a #6 (2.5 mm) set which calls for 26+ seconds on a Ford #4 viscosity cup. That is the biggest tip made for this equipment. I already have the #2 - #5 tips.
In hindsight, I then called Graco after buying the tip and talked to tech. Boy, did I get a lesson in spraying latex. I told him I had a #6 tip and would he please give me some guidelines on spraying latex. The first thing he said, was that he didn't think the #6 tip would work. Although with the remote pot, I could turn up the pressure and get a good flow, the turbine wouldn't be able to push enough air to atomize it. He was right and there went $90 down the tube. He suggested thinning the latex 10% and adding Floetrol. More thinning can change the sheen and bonding characteristics. Then start with a smaller tip. If I can atomize before I reach full air flow, then go to the next larger tip. When I get to a tip that won't atomize at full air flow, go back to the smaller tip. He said I would just have to live with the smaller output and subsequent slower coverage (it equated to a lot of time). I thinned the latex about 12% and added 8 ounces of Floetrol per quart of latex. That is the maximum Floetrol that supposedly won't change the sheen of semi-gloss or satin (I used satin), or change the color. Too much starts adding a yellow tint to the paint. I ended up with a #4 tip with a #3 air cap. The #4 tip is 1.8 mm. I went down to the #3 air cap because it is a higher velocity air flow for atomizing and does atomize a little better than the #4 air cap (this is a hint in the manual). It doesn't make sense because the viscosity suggested for the #4 is 20 to 26 seconds with the #4 Ford cup and the latex is so thick it would take minutes to empty the viscosity cup. I had already asked him about that earlier. He said that although the #6 calls for around 26 seconds, it could actually spray paints with viscosities up to 160 seconds. Also, all the tips can spray at much thicker viscosities that are listed in the manual. Although it will spray at higher viscosities, you must use a slower fluid flow so there is enough pressure to the air cap to atomize it. The viscosities suggested for each tip size is the optimal viscosity range for that tip; but it isn't the limit of viscosities that can be sprayed for each tip. Again, he was right. I could get good atomization, but I could only move the spray gun about 1 foot every 4 seconds or so. It took about 8-9 minutes for each door side. The material did have some orange peel and it splattered some as it went down, but with the Floetrol, it leveled out as it dried and I got a really smooth surface. I put it on pretty thick, so I could have easily gotten by with one topcoat, but I opted for two.
I do find that I can spray oil base paints to a really smooth finish much easier than latex with about 15% mineral spirits and 15% Penetrol. The sheen and adhesion don't seem to be affected. I use a #4 tip for that, too.
From the finishing newsgroup at Woodweb (http://www.woodweb.com/cgi-bin/forums/finishing.pl you might pose your question there), I get the idea that a conversion HVLP spray gun will handle heavier viscosities better than a turbine HVLP. I guess that is because you can get more atomizing pressure. For the conversion guns, it seems the consensus is Asturo or Kremlin. But be prepared to drop $400-$500 for the gun alone. However, with the conversion gun, your "spray rig" isn't very portable with a big compressor.
Obviously, for latex, the airless is still the way to go, but it is not very good in the shop for finishing cabinets and furniture.
BTW, I wouldn't even try to spray latex with less than a 4-stage turbine. It would take too much thinning or a way bunch of time.
Hope this helps,
Preston
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Yes. Thin it with water.
Rich

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You can use windshield washer fluid as well, the alcohol will evaporate quite rapidly.
Joe wrote:

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wrote:

Yes, but I find that "Floetrol" is essential for good results, the instructions are on the plastic jug. It's too cool to go out to the shed to read them!
Barry Lennox
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