In the world of surface texture, we talk about the size of the features that might impact an application. We use terms like form, waviness, and roughness to talk about the scale of features that may matter, depending on what the surface needs to do.
A golf course is a great way to visualize this. On the tee, the trees and larger hills will be your biggest concern. On the fairway (or off the fairway!) low hills and rough grass are the most critical. When you’re putting, the manicured grass and tiny undulations of the green will decide where the ball will roll. Hills, rough, and individual blades of grass… form, waviness, and roughness for a golf course!
But the heights of the hills and grass are just the start. On the green, the direction that the grass was mowed, cleat marks, even a random piece of debris can all ruin a putt. To find those subtle yet critical differences, you need to look at more than just the height of the grass…and if you are only measuring the height of the trees, you’d know nothing about these features at all!
If we’re talking about a painted surface rather than a golf course, we’d have similar concerns. The “hills” in a too-thick paint coat might give our finish an “orange peel” appearance, while smaller features might lead to a hazy finish. Grinding or polishing marks on the underlying metal might make the surface appear “brushed” in a way we don’t want.
Sometimes the anomalies matter more than the finish. Knowing the height of the fairway grass will not tell you how many sand traps are lurking around the green. You’d need a different way to find those, perhaps looking for local depressions with steep edges. On a precision surface, small, steep valleys like these could be locations where cracks could form or debris could be lodged, and that could lead to wear or failure.
And let’s not forget the most important features of a golf course: the holes! In all those yards of grass, trees and sand, there are 4 1/4″ inch diameter holes that you need to find. In a surface texture, tiny holes like this can have huge consequences as well. In a packaging film, say, pinholes could allow in air to spoil the contents. On the other hand, tiny bumps of this size may help two surfaces to slide without sticking.
Macro analogies like our golf course can be helpful when we’re trying to determine why surfaces aren’t behaving the way they should. What does the surface need to do? Would the trees or grass matter most, or maybe the holes, or the divots? Maybe all of those aspects be minor when compared to the hills? It’s a lot to think about!
But, try not to think about any of this while you’re putting…
Image: Andrew Shelley, Unsplash