Pinball Playfield Dimples — Causes, Prevention, and What to Expect

If you've ever looked at your pinball playfield under bright light at the right angle and noticed tiny dents across the surface, you've found dimples. They're one of the most discussed and most worried-about topics in the pinball world — especially among new owners who think their machine is somehow defective.

Here's the honest picture: what dimples are, why they happen, what you can and can't do about them, and why protectors make a real difference.

Dimples are small depressions in the playfield surface caused by the steel ball landing on it. Each one is typically a fraction of a millimetre deep — you generally can't feel them with your finger, only see them when light hits the playfield at a low angle.

They form because a steel ball is harder than wood and clearcoat. Every time the ball drops onto the playfield after an air ball, a ramp exit, a slingshot deflection, or a pop bumper hit, it transfers energy into the surface. The clearcoat flexes; the wood beneath compresses slightly; a tiny dimple forms.

Over thousands of plays, you accumulate thousands of dimples.

This is the part many new owners struggle with: every pinball machine ever made has dimples. Not most. Not modern Sterns. Every single one.

People sometimes look at a clean 1970s Bally or a vintage Williams and assume those old machines didn't dimple. They did. The dimples are there — you just need to view the playfield at the right angle in the right light to see them. Original-condition older machines that look smooth often have so many dimples accumulated over decades that the wood fibres have effectively been compressed flat across the whole surface, giving the illusion of smoothness.

This is sometimes called "the dimples levelling out." It's a real phenomenon — heavily played machines often look better than lightly played ones because the playfield has reached a kind of equilibrium.

On a brand-new machine, the first few hundred plays produce dimples that stand out against the pristine surrounding surface. Owners notice them, photograph them, and worry.

The problem feels worst between roughly 100 and 2,000 plays. Below 100, there aren't enough dimples to see clearly. Above 2,000-3,000, the dimples start to merge into a uniform texture that's less visually distracting.

Many owners find their machines look better at 5,000 plays than at 500. It's counter-intuitive, but it's the reality.

This question comes up constantly, particularly around modern Stern and Jersey Jack machines. The short answer: no.

Some clear coats are harder than others. Harder clear coats resist initial dimpling slightly better but tend to develop other problems — adhesion issues, chipping, separation around inserts. Softer, more flexible clear coats dimple more readily but tend to last longer overall. Manufacturers make trade-offs in formulation, but there's no clear coat formulation that eliminates dimpling on a wood playfield.

The wood is the bigger factor. Modern playfield wood is genuinely softer than the hardwoods used decades ago — old-growth lumber is gone, and replacement species are softer. This is a real industry issue, but it affects every manufacturer.

Practically speaking, no. A dimple is far too shallow to deflect a ball travelling at any normal speed. You can run your hand across a dimpled playfield and feel nothing.

What does affect gameplay is sunken or cupped inserts — where a plastic insert has dropped below the playfield surface by a measurable amount. That creates a real bump that deflects the ball. But this is a different problem from dimpling, and it has different solutions.

On a bare or clearcoated playfield, completely preventing dimples is impossible. The physics don't allow it. Steel ball, wood underneath — dimples will form.

You can reduce the rate at which they appear by:

Keeping the playfield clean and waxed — a well-maintained surface dimples slightly more gradually than a neglected one, though the effect is modest.

Adjusting the playfield angle correctly — too-steep angles cause more aggressive ball drops on ramp returns and air balls, increasing dimple formation.

Adjusting flipper strength and pop bumper power if adjustable — reducing the energy of ball impacts where you can.

But none of these prevent dimples. They just slightly slow accumulation.

A playfield protector genuinely makes a significant difference to dimpling. Here's why:

When the ball lands on a bare playfield, all the impact energy goes through the thin clearcoat and into the wood, which compresses to form a dimple. When the ball lands on a playfield with a protector fitted, the energy hits the PET-G plastic first. The plastic absorbs and distributes the impact across a wider area before it reaches the wood.

The result: a protected playfield develops dimples far more slowly. Owners who fit protectors from day one on new machines typically report virtually no dimpling visible under the protector even after thousands of plays.

The protector itself may show some marks over time — but the protector is replaceable. The playfield isn't.

If your playfield already has dimples and you're considering a protector, here's what you can expect. The protector won't remove existing dimples, but it will:

Visually smooth out the appearance significantly. The PET-G surface bridges over small dimples, so the playfield looks much smoother through the protector than it does underneath.

Stop further dimples accumulating in those areas.

Give you a flat, even ball-rolling surface regardless of what's underneath.

For machines where dimpling has become visually distracting, fitting a protector is one of the most effective ways to restore the appearance without expensive restoration work.

Dimples are normal. They're not a defect, they're not a sign of poor quality, and they don't affect how the machine plays. They are, however, visually noticeable on newer machines and can detract from the appearance.

If dimpling bothers you — or if you want to preserve the appearance of a high-value machine — a custom-fit playfield protector is by far the most effective solution. Fitted from day one, it dramatically reduces dimple accumulation. Fitted later, it visually masks existing dimples and prevents further formation.

For more on choosing the right protection method, see our comparison of Mylar and playfield protectors, or our complete guide to protecting your pinball playfield.