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Thread: Spraying Latex Paint

  1. #16
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    Feb 2003
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    Quote Originally Posted by Todd Hoppe View Post
    I have sprayed latex through an Grizzly LVLP gun, and sprayed general finishes waterborne Acrylic. Last night, I sprayed Zinsser BIN primer with the gun. A few suggestions:

    - Spraying latex stinks
    - Spraying Zinsser BIN primer is worse. It flowed better, but cleanup stinks.
    - It was a true pleasure to spray the General Finishes product. It is meant to spray, and the finished product makes me actually look like I know what I'm doing.

    I'm all for the economy of latex paint. If you use a product designed for spraying in various types of spray equipment (not just airless) you will never regret it.
    Todd, you have some interesting remarks. Spraying latex has become a controversial topic. I would suggest one read the label of the product they are using before application. If you use the right equipment, spraying latex is "fun".
    What's up with the Bin primer? Great product. Sprays well through siphon guns or HVLP turbines or conversion guns. You need to thin with alcohol and strain it before using it. I've used it for over forty years. Wonderful primer.
    What is the "economy" of latex paint? Do you mean the ecology factor of water base paints?
    Just curious.
    Phil in Big D
    The only difference between a taxidermist and the taxman, is that the taxidermist leaves the skin. Mark Twain

  2. #17
    After struggling with this myself I took the time to learn the science. Some pretty funny internet ideas out there on what works. Additionally there are big differences in HVLPs and I must admit, a conversion gun with pressure feed solves a lot of problems. If you read the real professional coating engineering literature(trust me this sucks), you will just buy an appropriate viscosity cup and learn how to match it to your needle or you are just wasting your time on an art when you could solve the problem as a science. (what you learned in solvent lacquer school doesnt work) It doesn't matter if you have a bleeder, non bleeder, conversion siphon, conversion pressure, gravity in any number of combination, you need to understand that the particular gun must atomize the particular paint to work. I have two seemingly identical latex primers and one will go through a 4mm viscosity cup and the other will not so it becomes apparent that thinning will not help and you must change the needle.

    Why windshield washer fluid? Lets look at rheology. When you use solvents to thin solvent based paints, the solvents are very very thin compared to water with very low surface tensions (ever look to see massive acetone beading on a surface?) . For instance Varsol will flow through brass but water will not so rheology and its subscience viscosity are what you need to understand. If you add 30% lacquer thinner to lacquer, you are only diluting it, BUT waterborne paints can only allow up to 10 % water in the interstitial spaces (materials science term for little holes) so the dilution to 10 % for water is correct. What they don't tell you is that you can add additional alcohols and they have no real effect on cure before they flash but they reduce SURFACE TENSION. If you buy windshield washer fluid for latex primer you get to add 10% water plus the methanol and get a far bigger bang for you buck than adding water but I never figured out the whole % of windshield washer you can add but 30% is pretty high and can affect the coating crosslinking quality. (we dont want our product to peel, lift or behave badly and Methanol is hardly low VOC. )

    You should really buy the correct viscosity cup and based on your results pick the right needle as the point is to put product on, not something that evaporates and pollutes. The viscosity of waterborne coatings is double important with gravity cups as you can paint yourself into insolvency. I am not a hundred year expert on spraying coatings but with a little research, an inexperienced newbie can get the basics down quickly but experienced people will have to unlearn bad habits. These advanced coatings are not stone age technology; quit using stones as life will pass you by. If you plan on doing spraying waterborne, buy a good HVLP gun with many sizes of needles or many HVLP guns with different needles.

    I think Lemmer alluded to it correctly, you want to put 200ml of product on a minute, not 50ml of product and 150ml of nothing.

  3. #18
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    >>>> Is it OK to dilute latex that much (30%)

    No, not without speaking to the tech support from the paint manufacturer. I have never seen a situation where thinning of a waterborne paint was greater than 5%.
    Howie.........

  4. #19
    It is not OK, it never was OK as waterborne are not solvent based and do not act like solvents. The actual product compounds we desire are the same ie shellac, cellulose, urethane acrylics and vinyls are the same but the carrying system is not. Pick the right tip and like you said, almost nothing needs to be added.

  5. #20
    there is a excellent waterborne technical white paper by Bayer Material Science and a practical one by Target. Homebrewed chemistry is incompatible with the advanced waterborne formulations.

  6. #21
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    Why do people persist in speaking of Latex paint, a name mostly of historic interest compared to the variety of today's waterborne paints. Paints marketed as Latex these days are almost always formulated to be used on walls and ceilings, and generally with rollers, brushes, or by pros using airless sprayers. Viscosity is set to be desirable with those methods of application. But, there are a host of paints some from the pro-companies such as Sherwin Williams and others, such as Target and General Finishes. In the cases viscosity has be tweaked to be ideal for spraying with hvlp guns with only minor tweaking. Some of these have been designed to mean kitchen cabinet certification requirements or be otherwise be made to be used on wood products including furniture. The manufacturers will almost never call these latex paints.

  7. #22
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    Alcohol does help to beat the surface tension. I guess that's why the washer fluid works. I've heard strong moonshine works pretty good too. We still use Latex on walls.

  8. #23
    Quote Originally Posted by Steve Schoene View Post
    Why do people persist in speaking of Latex paint, a name mostly of historic interest compared to the variety of today's waterborne paints. Paints marketed as Latex these days are almost always formulated to be used on walls and ceilings, and generally with rollers, brushes, or by pros using airless sprayers. Viscosity is set to be desirable with those methods of application. But, there are a host of paints some from the pro-companies such as Sherwin Williams and others, such as Target and General Finishes. In the cases viscosity has be tweaked to be ideal for spraying with hvlp guns with only minor tweaking. Some of these have been designed to mean kitchen cabinet certification requirements or be otherwise be made to be used on wood products including furniture. The manufacturers will almost never call these latex paints.
    "LATEX" is the general term for for water based paints. Take Sherwin Williams ProClassic for example, it is marketed as "ProClassic Interior Acrylic Latex Enamel"

    What is important to woodworkers is the binder - which preferably is 100% acrylic. (which is the binder that most of the 'good' latex paints use). I use 100% acrylic Sherwin Williams 'Super Paint' or 'Duration' on my walls applied with brushes and rollers. I Use ProClasic ENAMEL on my trim and woodworking projects - it is still 'latex paint'

  9. #24
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    >>>> Is it OK to dilute latex that much (30%)

    Only if you contact the manufacturer's tech folks and see what they say. I have never heard of a waterborne acrylic manufacturer recommending thinning beyond 5% or so.

    Are you really using a latex or is it really a waterborne acrylic? I believe what you are using is a waterborne acrylic. True latex is only infrequently used these days and is really only for wall and ceiling paints.
    Howie.........

  10. #25
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    Feb 2003
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    Shoreline, CT
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    Latex is still used by some companies marketing paints to consumers or commercial painters. The paints mentioned are good examples of high quality but still consumer grade coatings. But, there is a whole different category of coatings, with the marketing focused on industrial users. These are very unlikely to call them selves latex paint. They are usually too thin to be easily brushed or rolled. That of course makes them easier to be applied by conventional or HVLP spray equipment.

    By the way, latex doesn't refer to natural rubber, which has long disappeared from coatings. It refers to the little "packets" of the finish that are emulsified into water. These packets are similar in form to packets of natural rubber emulsified into water that makes up latex sap that is tapped from rubber trees.

  11. #26
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    Jul 2014
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    Steinbach, Manitoba, Canada
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    Hi Doug,
    I'm a new member and don't know much about forums. But here's my two cents worth! I use a small Graco gravity feed HVLP gun with a small cup (to allow access in tight spaces), and I spray latex furniture paint onto chairs, cupboards etc. All I do is thin it a bit using H2O. I dial in the ideal pressure (usually around 40 PSI), pattern and flow, and spray away! It does dry a lot slower, but it is amazingly durable. I know this because my wife distresses the pieces I paint, and it takes a fair amount of pressure with a wooden sanding block to rub off paint on the edges of the project. When I clean the gun, I always run some paint or lacquer thinner through it to avoid possible corrosion.
    Hope this encourages subsequent seekers of spray painting truth...
    Cheers,
    Al Derksen

  12. #27
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    Dec 2010
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    Well, a couple of you get it. Latex means nothing more than water emulsion of a synthetic polymer. Wall paint, waterborne acrylic, whatever, if it's a synthetic polymer water emulsion it's generically latex. As some have said, wall paint is a poor choice for furniture but it's because of the polymers used for the intended application, walls, not because it's a latex paint. Waterborne acrylic paints may or may not be good for furniture applications, it depends upon which specific acrylic polymer(s) were used and, yes, it's still a latex paint.

    You don't need to call the manufacturer to find out how much you can dilute it and what to use, and I'm sure they prefer you don't. There is this thing called the internet now and just about every manufacturer posts their tech. data sheets and MSDS there for their customers' benefit. With the waterborne acrylic paints I've used they can be diliuted at least 10% with water. You have only to read the can or tech. data sheet to find out what diluent and and how much can be used.

    There are excellent waterborne paints/finishes now, formulated in viscosities appropriate for HVLP guns, and others for airless sprayers. A little research will take you a long way towards narrowing the list to fit the equipment you have and application needs.

    John

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