# Do I need to thin water based polyurethane when spraying ?



## Carloz (Oct 12, 2016)

Do two stage HVLP such as Fuji Semi Pro 2 or Earlex 6002 ( 5 and 4.5 psi) have enough pressure to spray General Finishes High Performance Water Based Top Coat ( What a name !!! ) without thinning ? The manufactures are vague on this.


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## wapakfred (Jul 29, 2011)

I've sprayed it with my Fuji 4 stage and a 1.8mm needle set though I think I did thin it 10% with water. Be careful to not add more water than the manufacturer says, it can screw up the coalescing process.


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## Carloz (Oct 12, 2016)

Just found it: The guy from General Finishes. sprays it with a much less powerful Earlex 5500 without thinning.


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## AlaskaGuy (Jan 29, 2012)

It would really be nice if finish manufacture woulds would put the viscosity time on the label.

Example: 25 seconds in a #4 ford cup. It would make it so much easier to pick a spray tip size and pressure.

http://homesteadfinishingproducts.com/wp-content/uploads/2014/05/paintspraying_ver3.pdf


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## rwyoung (Nov 22, 2008)

Viscosity is given on the technical data sheet (but not the label).

https://generalfinishes.com/sites/default/files/file_downloads/tech-data-ef-high-performance-poly-2014-07-28.pdf

Given as 35-45 seconds with a Ford #4 at 77F. Quick survey of Fuji manual suggests they want 15-18 seconds for polyurethenes and the 2mm N/N set. However this could be the wrong manual.

All such numbers extracted from manuals and data sheets are merely starting points for setting up the system(s). Test prior to spraying a project. Big sheet of cardboard makes a good target, reasonably simulates spraying a wooden surface.


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