Graco FFLP tip problems?

[wptski]

In another forum a user mentioned "tip shear" which I've never heard of so I Googled that and found this thread in yet another forum:http://www.painttalk.com/f6/new-graco-fine-finish-tip-74593/.  It's where spraying paint changes its sheen.  If paint is sprayed, any touch ups are taken from a container of sprayed paint not the bucket it came in!

Seems the new FFLP tips might be a bit touchy when used in anything not designed for it or the product used.  Scott Burt?

 

[Scott B.]

Bill

I followed the link, that discussion is kind of all over the road.

Shear is a term used to describe what happens in an airless tip during atomization. It is very different from the droplets formed in HVLP spraying.

Issues related to sheen in spraying usually come up when guys add extenders. Its a really bad idea and unnecessary in spraying. Easiest way to mess up sheen.

It is definitely a good idea to keep the spray batch for touch ups so that it is identical.

 

[wptski]

Scott:

So what do you say, do the FFLP tips exhibit more shear than the FF tips??

 

[Scott B.]

Scott:

So what do you say, do the FFLP tips exhibit more shear than the FF tips??

All airless tips shear paint. Its a violent transformation of liquid to vapor in about an inch of real estate. So, how you observe it is completely dependent on your product, tip selection and how you dial it in.

It isn't an issue that I have heard about or observed.

If it did happen, like a guy is standing there saying "Darn, this tip is just shearing my paint too much", the obvious thing to do would be to look at orifice size and fluid pressure.

 

[tiralie]

I followed the link, that discussion is kind of all over the road.

LOL. Thanks for saving me the time chasing that rabbit hole.

Shear is a term used to describe what happens in an airless tip during atomization.

Agreed. Otherwise known as Thixotropy. In the case of airless machines the sheer properties of the paint are disrupted by hydraulic forces . Once applied and the energy is dissipated, the paint then returns to it's previous viscosity. My understanding (I could be wrong) is sheer is a reference to the amount of energy it takes to actually atomize a coating based on it's viscosity. In the can some paint is formulated to actually adhere to vertical surfaces and therefore reducing sheering causing drips and runs.

Issues related to sheen in spraying usually come up when guys add extenders. Its a really bad idea and unnecessary in spraying. Easiest way to mess up sheen.

Agreed, which is why all manufacturers recommend not thinning more than a recommended amount.

 

[wptski]

Well from experience with the FFLP tips, I can say I have touched up an exterior paint with a foam brush that was originally sprayed with my Graco. No perceptible difference in sheen.

The touch up paint used was from the container and "not" from what was sprayed into another container?

 

[wptski]

Touch up came from original paint can. Not sure if I am following the question though.

That's the test for shear.  If you spray the product, touch up from the original paint can and the sheen is different then the spray tip has affected the sheen.  That's why some spray into another container to use for touch ups.

 

[tiralie]

Touch up came from original paint can. Not sure if I am following the question though.

That's the test for shear.  If you spray the product, touch up from the original paint can and the sheen is different then the spray tip has affected the sheen.

That is incorrect. I believe you have misunderstood Scott's post.
Tim

 

[wptski]

That is incorrect. I believe you have misunderstood Scott's post.
Tim

I'm going by the linked thread I posted, it's explained just as I did.  Even one of Scott's posts above suggests using the sprayed product for touch ups to be sure sheen matches.

 

[tiralie]

I'm going by the linked thread I posted, it's explained just as I did. 

@Bnaboatbuilders experience proves the opposite. He touched up a sprayed surface with a coating from the can.

Even one of Scott's posts above suggests using the sprayed product for touch ups to be sure sheen matches.

True, It is always a good habit to touch up from the paint that was used to spray, particularly in the case of using (too much) thinner or extenders. Scott didn't say sheering itself created sheen differences, but that the use or abuse of extenders, worn or faulty equipment or over thinning were usually the issue.
Tim

 

[wptski]

@Bnaboatbuilders experience proves the opposite. He touched a sprayed surface with a coating from the can.

Tim

I wasn't disputing his answer but he said, "Not sure if I am following the question though".  Results may vary among users depending on product, etc.  We don't paint in a lab!  [big grin]

 

[Scott B.]

I'm going by the linked thread I posted, it's explained just as I did. 

@Bnaboatbuilders experience proves the opposite. He touched a sprayed surface with a coating from the can.

Even one of Scott's posts above suggests using the sprayed product for touch ups to be sure sheen matches.

True, It is always a good habit to touch up from the paint that was used to spray, particularly in the case of using (too much) thinner or extenders. Scott didn't say sheering itself created sheen differences, but that the use or abuse of extenders, worn or faulty equipment or over thinning were usually the issue.
Tim

Correct.