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Discussion Starter · #1 ·
There's been a lot of chatter here lately about all of us ignorant painters who use FFLP tips causing tip shear/paint shear. I'm not discounting the fact that tip shear is real, and I understand that the manufacturer's recommendations for tip sizes would suggest using an orifice nearly double in size than what I use for many products, but I'd argue those recommendations were written long before the advent of low pressure spray tips. Think about it for a minute...wouldn't tip shear be a result of a combination of too high of pressure pushed through too small of an orifice? Surely we wouldn't be shearing paint if we used those small orifice tips at no more pressure than a garden hose, right? If that's true, then I'd argue that if low pressure tips are allowing you to spray at nearly half the pressure of what you'd otherwise have to spray at, wouldn't the risk of shearing also be reduced proportionately?

I'm not speaking as an authority by any means. This is only my reasoning as a dumb painter. I think I have a relatively descent grasp on the effects of shear, how it relates to rheology, products & pigments which are more prone to shear, potential issues caused by shear, but claims have been made on here about paint failure as a result of shear. How would one go about proving that failure was caused by shear anyway?

It's also been postulated that manufacturers suggest using larger orifices than what would be reasonable to eliminate the risk of having to pay for paint failures caused by shear. From a conspiracy standpoint, one could instead claim that by manufacturers suggesting larger orifice tips, we use more paint and make them more money. But I don't want to get sidetracked here.

Can you provide a link or citation to a product failure as a result of tip/paint shear?
Not a theory or a story.
An actual case that's been proven & documented. I'd genuinely love to read and learn about all those documented failures caused by tip shear.
 

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Discussion Starter · #4 ·
Classic! Hope you've got a giant tub of popcorn and are younger than 40.
Yes to popcorn
No to under 40
46 actually, but with my new hair style, my wife says I don't look a day over 45 and a half.
 

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HOLD MY BEER!
https://cdn.technologynetworks.com/TN/Resources/PDF/WP150713PaintsCoatingsRheology.pdf

And i would suggest calling Graco, Binks, Titan, Spraytech, Devilbiss, Airlessco, and any other brand name airless or conventional spray equipment manufacturers technical service and ask them. Don't ask your local rep. They may or may not have a clue. It actually has to do with the volume of paint being forced through the orifice and not so much the pressure. Read the article, do the math, be amazed.
 

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I was being a dork and reading a couple Pds for some different products. Two things jumped out at me. Breakthrough 250 and I believe the 50 version both mention spraying with fine finish tip and recommend a tip size of 09 through I think 11. Also when stating the product uses the 250 version says for cabinets and the 50 does not.

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basically, an acrylic resin molecule is a pretty complex and fairly large molecule. If to much of it is forced through to small of an orifice, the molecules can be smashed or ripped apart in such a way that they no longer perform as the were designed. That can be a barely noticeable cure difference to a complete failure to cure. They can also become brittle to the same varying degrees that may or may not effect the durability of the finished product. They may become less viscous which will lead to excessive sag. Again, the degree of this is variable. There are so many variables to how the 100's of acrylic resins will be effected that the paint company chemists test the product to determine which orifice sizes will not in any way effect the performance of the paint. That is the orifice size or sizes that are recommended in the data sheet. If you feel it is better for you to test the product you are using with a fine finish tip on a paying customers paint job than that is fine. Just don't expect the paint company to stand behind the product if it does fail. That is pretty much what i have said. FF tips may or may not cause an issue depending on hundreds of variables.

An example, in another thread on PT that i have not replied to, a painter is having classic paint shear problems when spraying Breakthrough. Now that product is specifically engineered to be able to withstand high shear rates, and the data sheet specifically says that the use of fine finish tips is recommended on jobs that require them. So what is causing his problems? I don't know. There could be any number of slight variations in the paint that could be causing his problems and the only way to find out what it is would be to test the product in a lab. So what about paints that aren't engineered for FF tips? How many variables do you think there are that could cause a paint failure? A bunch.

So is using a FF tip with a non-compatible product a risk worth taking? That's your choice. But the data sheets give you the recommendation of the chemists. And that's that.

But i see shear related failures on trim, cabinets, doors etc. on a fairly common basis. They sometimes don't show up for years to be honest with you. But i see them. And usually recoating that surface SHOULD require that coat to be removed but it rarely happens.
 

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Discussion Starter · #12 ·
I was being a dork and reading a couple Pds for some different products. Two things jumped out at me. Breakthrough 250 and I believe the 50 version both mention spraying with fine finish tip and recommend a tip size of 09 through I think 11. Also when stating the product uses the 250 version says for cabinets and the 50 does not.

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I've read those sheets as well. I'm guessing PPG updated/modified their data sheets to differentiate the 50 from the 250, which is a good thing, and likely included the FF tips when the data sheets were updated. Their recommendation for tip orifice is the first I've seen to include as small as .009, and they suggest using that with 2,000 psi, (which is far more pressure than I'd ever attempt). I know it's important to consider the contents of each product as it relates to spray recommendations for tip sizes and orifice size, but clearly they wouldn't be stating this in writing if we were shearing their paints by following their recommendations.
 

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Once again, all theories, hear-say, and not one single picture of a tip-shear failure....

I dont disbelieve what you are saying, but LETS SEE A REAL WORLD EXAMPLE. I've seen hundreds of real world examples of paint sprayed with too small a tip that turn out great. I have ZERO real world examples of an actual tip failure.
 

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No one believed in black holes either but here we are! Staring at an event horizon that they call a black hole! Don't get me started on that one! As soon as i can get a decent pic i will post it. (now that i say that it will probably be months before i see another one!)
 
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