While helping raise our six children, two of them girls, I often found myself accused of being too insensitive. I have seen that sensitivity can be a double-edged sword. “Oh dad, you’re so sensitive” can be a very endearing compliment in the right setting depending on how it’s delivered - say during a private conversation at home, with but not in a cowboy bar in Dallas. Somebody described as insensitive could well be a very empathetic and skilled listener - or touchy and prone to flying into fits of anger. I’m guessing we all know people who are both.
Is sensitivity good or bad when it comes to retroreflective sign sheeting?
“Sensitive and insensitive” sheeting designations sprang into our industry once researchers and agencies confirmed something that Avery Dennison has understood since making our first prismatic sheeting. Prisms, by virtue of being an asymmetric 3-sided structure, do not return light in the same way as spherical glass beads. Rotate a glass sphere around its axis and you still have a round sphere with the same optics. But rotate a 3-sided prismatic element and you get something quite different, and when incorporated into retroreflective sheeting, a product that does not have the same uniform performance experienced with glass beaded sheeting.
This difference led to new designations in the latest AASHTO M 268 sheeting specification. Rotationally sensitive and rotationally insensitive sheetings are now standard classifications.
- Sensitive = retroreflective performance has more than 20% difference when rotated
- Insensitive = retroreflective performance has less than or equal to 20% difference when rotated
Measured rotation angles are shown in this figure.
Which is better?
While both sheeting types can be used successfully to create highly visible signs, the consequence of the designation can be found within the sign fabrication process.
- Sensitive sheetings must be handled with special care by sign fabricator. The material is at its optimal performance when applied to substrate and oriented so that the production datum arrow/marks run vertically. This holds true for all sign shapes - the datum marks should run vertical - not horizontal, robbing a sign fabricator of inventory flexibility. In typical manufacturing practices sheeting is applied to diamond shaped warning signs perpendicular to the edge of the aluminum substrate, not in the direction that the aluminum is rotated when installed on a sign post. This is a major concern for sensitive sheeting since it’s 45-degrees off of the sheeting’s manufactured orientation. The full retroreflective property of the material will not be achieved - like buying a triple decker ice-cream cone and immediately throwing the top scoop into the trash. For sign fabricators cutting out letters and numbers for guide sign legend, the inability to fully nest letters and numbers can result in material waste of 20% or more.
- Insensitive sheeting may be applied to the substrate in any direction most preferable to the fabricator and still achieve optimal performance. Squares, rectangles, circles and diamonds - uniform performance can be expected. Computer cut letters can be nested to most efficiently maximize material yields and hold down costs.
Pictures being worth a thousand words, here’s an example of sign legend and border showing the visual appearance of sensitive sheeting, but produced and applied without regard to proper orientation.
The Avery Dennison solution
Microprismatic replication has been our passion starting with Model T tail light reflectors produced close to a century ago. Overcoming the asymmetric nature of cubed corner sheeting is technologically challenging, but we’ve solved this with problem by creating tiles, or blocks of prisms that are then placed into our sheeting in multiple orientations. The result is insensitive sheeting with uniform visual performance for drivers and time and money saving features for sign fabricators. No worries and no waste.
We call this solution omni-directionality, and it’s what we mean when you see our “Smart at Every Angle” slogan. This feature is in all traffic prismatic sheeting we produce. And don’t forget, Avery Dennison was the first to manufacturer microprismatic sign sheeting - the staple of today’s modern traffic signage globally.
Together we can end bad behavior
Sensitive or insensitive, you need to know how your brand of prismatic sheeting behaves and take precautions to use it properly in order to optimize sign performance. Be sure that you address orientation sensitivity in your own specification, and with your shop crew. We’re happy to help with suggestions that will allow you to achieve the finest highway signing. Click here for more details on rotational sheeting performance.
Visit us on the web to see all of our innovations, from omnidirectional sheeting to solid layer vehicle conspicuity safety tapes. See how the TrafficJet™ Print System, the industry’s best-selling digital print platform for fully-warranted and specification compliant traffic signage is revolutionizing the way traffic signs are produced.