Sandpaper is primarily gauged by its grit, which indicates the coarseness or fineness of the abrasive particles on its surface. The grit number refers to the number of abrasive particles per square inch; a lower number signifies fewer, larger particles, resulting in coarser sandpaper, while a higher number means more, smaller particles, leading to finer sandpaper.
Understanding Sandpaper Grit Levels
The grit system provides a standardized way to select the appropriate sandpaper for various tasks, from aggressive material removal to delicate finishing. Here's a breakdown of common grit levels and their classifications:
| Grit Number | Classification | Common Uses |
|---|---|---|
| 40 Grit | Coarse | Heavy material removal, initial shaping, stripping old paint or varnish. |
| 80 Grit | Medium | Moderate material removal, smoothing rough surfaces, preparing for finer grits. |
| 100 Grit | Medium | General sanding, preparing surfaces for staining or painting. |
| 120 Grit | Fine | Light sanding, smoothing out scratches from coarser grits, preparing for topcoats. |
| 220 Grit | Fine | Final sanding before painting or staining, smoothing between finish coats. |
| 440 Grit | Extra Fine | Polishing, very light scuffing between clear coats, achieving a smooth finish. |
Practical Application of Grit Gauging
- Start Coarse, Progress Finer: For most projects, you'll begin with a coarser grit to remove imperfections or old finishes and gradually move to finer grits to achieve a smooth, refined surface. Skipping grits can leave visible scratches.
- Material Compatibility: The ideal grit depends on the material you're sanding. Wood typically requires a progression from medium to fine, while metal or plastics might need different abrasive types and finer grits for polishing.
- Desired Finish: Your ultimate goal determines the final grit. For a rough, rustic look, you might stop at a medium grit. For a mirror-smooth, high-gloss finish, you'll progress to extra-fine grits and even polishing compounds.
Gauging sandpaper by its grit ensures you select the correct abrasive tool for effective material preparation and achieving the desired surface finish.
