What is Paint Shear?

The small metallic flakes in today’s paints, combined with pigments and their other structural elements, give cars and trucks their consistent, spectacular shine and add to their durable finish.

But these same particles that provide the beautiful finish, are both damaged by and wear on the equipment they flow through. This can lead to paint degradation due to something known as shear. In fact, one of the paint system’s components - the back pressure regulator or BPR - is a major contributor to paint shear.

Think of the flow of traffic like flowing paint, and the cars that make up the traffic as the metallics in the paint. 

• When the cars travel down an easy road in the same direction, there are few collisions and they retain their shape. 
• When the cars drive in a busy city, it’s more like a maze with abrupt curves and intersections. The vehicles collide with each other and barriers, and they don’t look the same for long. 

So it is in flowing paint.

• Metallic flakes or particles collide against each other as the paint moves through circulation system equipment, especially the back pressure regulator (BPR).
• The subsequent paint damage or paint degradation leads to variation in appearance and a less durable coating.

All of that spells wasted material, money, time and energy. Such waste impacts the environment, especially when you need to discard the damaged paint.

Whether or not paint has metallics, there always will be some amount of shear.

A well-designed back pressure regulator (BPR) can lessen its impact on total system shear. It’s like the easy road for your paint. Larger ports and gradual geometries lead to less collisions between the metallic particles themselves, as well as the BPR surfaces, and therefore promote lower shear.

Graco’s low shear back pressure regulator (BPR) reduces paint damage by incorporating gentle inlet flow geometry, unique fluid housing geometry, and a cone-shaped flow director. Those unique features work together to reduce flow velocity and evenly distribute flow through the BPR. This video shows how.