This is all about grit progression, which is starting at a low (coarser) grit and moving up to higher (finer) grits, step by step. The Golden Rule of Sanding means not skipping more than one grit through each step of sanding a surface. This is a basic rule anyone should follow whether they are working with metal, wood, or any other surface.

Every scratch you make must be removed by the next finer grit. Skip a step, and you risk locking in scratches that show up only after staining or coating—wasting time, materials, and your sanity.

Why the Golden Rule Exists

When you sand something, you're not just smoothing it out…you’re actually carving thousands of tiny scratches into it. That’s what sandpaper does. The coarser the grit, the bigger and deeper those scratches are.

The job of the next grit isn’t just to make things smoother. It’s to erase those deeper scratches from the coarser grit before it. Each successive grit replaces the larger scratches with smaller, shallower, and more numerous ones, gradually refining the surface towards the desired level of smoothness. This methodical refinement is the heart of the Golden Rule.

The whole idea behind the Golden Rule is that each grit sets the stage for the next one. You’re not sanding just to “sand”—you’re refining. One layer of scratches is replaced with a finer one, then another, until you get that clean, smooth surface that’s ready to shine.

For more about sanding grit, check out this blog post - Sandpaper Grit Explained

The Consequences of Breaking the Rule

Jumping from one grit to a much higher one can be tempting. You may think that it is going to save you time and require less sandpaper, but this shortcut almost always compromises the final quality and can actually winds up increasing your total effort required.

When you skip grits – for example, moving from an 80 grit directly to a 180 or 220 grit – the finer abrasive particles lack the necessary cutting power to effectively remove the deep valleys created by the coarse grit. Instead, the finer grit just sands down the peaks of the existing scratch pattern, leaving the deeper valleys largely untouched.

This leads to several problems:

• Uneven Surface and Swirl Marks: The surface will have an inconsistent scratch pattern, with deep valleys remaining beneath superficially smoothed peaks. This often shows up as visible sanding swirls or an uneven texture, especially noticeable under a finish.
• Poor Stain Absorption (Blotching): When stain is applied to a surface with deep scratches, the pigment collects in these valleys. This results in a blotchy, uneven appearance with darker areas where the unremoved coarse scratches are.
• Reduced Finish Clarity and Adhesion: The uneven surface can interfere with the clarity and adhesion of film finishes like lacquer or varnish. A finish may pool in the deeper scratches, leading to less coverage and potentially premature wear as the finish on the peaks wears away first.
• Increased Sanding Time and Effort: Trying to remove deep scratches with a much finer grit is not the most efficient use of your time. It forces the finer grit to do work it wasn't designed for, requiring significantly more time and physical effort (over-sanding) to achieve even a passable result, often without fully correcting the original problem.

Choosing the Right Grit Sequences

The Golden Rule calls for progressive sanding, but there's no single, universally perfect grit sequence. The ideal path depends on several factors:

1. Starting Surface Condition: A rough-sawn piece of lumber requires a much coarser starting grit than a piece already smoothed by a planer with sharp blades. Pre-sanded plywood might only need starting at 120 or 150 grit.
2. Material Type: Hardwoods generally allow for starting with coarser grits (like 80) compared to softwoods (often starting at 120 or 150). Metals vary too; heavy rust might need 40-60 grit, while smoother metal could start much finer. Aluminum requires finer grits and care due to its softness.
3. Tools Used: The aggressiveness of the sanding tool influences the effective cut of a given grit.
4. Desired Finish: This is often the most crucial factor, especially for the final grit.

Don't Skip More Than One Grit

Sanding through every single available grit could definitely work, but that’s overkill and more work than anyone wants to do. Skipping some grit levels is often efficient enough for most sanding projects. Just make sure you follow the "50% Rule" or "Don't more than double" rule: the next grit number should be no more than roughly 50% higher than the previous grit (e.g., after 80 grit, the next should be max ~120 grit) or less than double the previous grit number. This is to make sure each grit can effectively remove the scratches from the one before it. 

• A jump from 80 to 120 (skipping 100) is generally acceptable.
• A jump from 80 to 150 (skipping 100 and 120) is not recommended.
• A jump from 150 to 220 (skipping 180) is acceptable.

FAQ

Q1. What is the Golden Rule of Sanding?

The Golden Rule of Sanding is to never skip more than one grit level when sanding a surface. Each finer grit must fully remove the scratches from the previous grit to avoid defects like swirl marks, blotchy finishes, and poor coating adhesion.

Q2. Why shouldn’t I skip sanding grits?

Fine papers can’t remove deep scratches from coarse grits. You’ll end up redoing work.

Q3. How many grit steps do I really need?

Usually three to four: coarse, medium, fine, and final prep.

Q4. How do I know when to move up a grit?

Move up a grit when the scratches from the previous grit are completely removed and the surface has a uniform scratch pattern. If any deeper marks remain, stay with the current grit longer before progressing.

A common trick is to lightly draw pencil lines across the surface before sanding. Once all the lines are gone, it means you've sanded evenly and can move to the next grit.

Q5. Does metal sanding need different steps?

Yes. It often requires tighter grit jumps and optional wet sanding for high-gloss work.

Ready to Upgrade Your Finish Game?

Whether you’re sanding wood, metal, or anything in between, following the Golden Rule of Sanding is the difference between a flawless finish and hours of frustrating rework. Don’t rush the process—take it one grit at a time, and let each pass do its job.

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