On Sat, 27 Nov 2010 11:54:36 -0500, "J. Clarke" wrote:

In article ,
says...

J. Clarke wrote:
In article ,
says...

blueman wrote:
As a newbie to HVLP, I have encountered the following problem...
I am spraying Minwax (water-based) Polycrylic semi-gloss
polyurethane.

FYI, polycrylic is not polyurethane. It is acrylic and urethane is
*MUCH* harder and therefore scratch resistant.

Don't assume that harder means more scratch resistant.


Scratch resistance is one of the defining characteristics of hardness.

So tell us the engineering definition of "hardness" and quote your
source.

"The Mohs scale of mineral hardness characterizes the scratch resistance
of various minerals through the ability of a harder material to scratch
a softer material. It was created in 1812 by the German mineralogist
Friedrich Mohs and is one of several definitions of hardness in materials
science."

http://www.search.com/reference/Mohs...neral_hardness