How to flamepolish plastics to remove scratches and dull hazy spots

This article explains how to flame polish the plastic ramps of a pinball machine. It’s a technique used to remove scratches from acrylic plastic and restore parts to their original, like-new appearance. By briefly heating the plastic with a hot flame, the surface melts and becomes smooth. I hope you enjoy this flame polishing tutorial.

Warning: The author of this page cannot be held responsible for any damage incurred while attempting this technique. Use at your own risk! I want to be absolutely clear—don’t complain to me if you melt your precious ramp! Flame polishing is dangerous!

Introduction to flame polishing

Anyone who has closely examined pinball machine flyers will have noticed: brand-new plastic ramps are shiny and crystal clear. In photos, you often have to look carefully to even spot the ramps, they’re that transparent! Compare this to a well-used pinball machine, and you’ll see the ramps are cloudy, scratched, and barely see-through.

Fortunately, there’s a way to make used ramps look like new again: flame polishing. By heating acrylic plastic, the top layer melts and smooths out. Small imperfections and haze disappear. Sounds easy, right?

I first saw flame polishing being done in the This Old Pinball DVD #4 (Indiana Jones). Flame polishing is something you should watch being done before attempting it yourself. Especially if you don’t have spare ramps to practice on.

I had heard about flame polishing for over a year before I finally tried it on my own machines. I bought a Theatre of Magic. One broken ramp was replaced with a brand-new one. I wanted the other ramp to look as good as possible, because a shiny game with one new ramp and one old one just doesn’t look right. Flame polishing was the only solution, and it had to be done properly.

I must say, it worked very well. It’s hard to tell which ramp is the old polished one and which is brand new. I’m certainly no expert in flame polishing, I still have a lot to learn and experiment with. But I’ve already discovered some useful insights, and I want to share what can go wrong so others can learn from my mistakes.

Again, a warning: flame polishing isn’t for everyone! It’s risky. If you’re not careful, you can ruin your plastics. If you don’t have ramps to practice on, but your game has a ramp under the playfield, start with that one. If you mess up, at least it won’t be visible.

Conditions for flamepolishing

Flame polishing works on translucent ramps from pinball machines made since the 1990s. It has no effect on non-translucent ramps (like the black plastic ramps used on 1980s games), which don’t suffer from haze. Scratches on those can be better removed using plastic polish.

Some ramps may be made from different types of plastic that burn or melt at different temperatures, so be cautious if a ramp looks or feels unusual. This technique works best on acrylic plastic.

The small blue ramp on Bally’s Strange Science is one you should avoid as its plastic is too thin. Also, be extremely careful around the thin part of the Whitewater whirlpool ramp, as shown in the picture!

Playfield windows like those in Creature from the Black Lagoon, Popeye, Black Hole, and Haunted House can also be flame polished, though I haven’t tried this myself. I also haven’t tested ramps that have been glued or repaired with resin or epoxy. These materials may react unpredictably to heat.

This technique is intended to remove small scratches and haze. It won’t fix holes, breaks, or deep scratches. Yellowed plastics will remain yellow. You can use flame polishing on other translucent plastics and bumper caps, but be cautious,they can burn quickly.

Required tools to flame polish

You’ll need a torch. There are several types available. I’m no expert. I use a small one; larger torches may be too hot. Others prefer a large butane torch, but you need to have experience with them and work fast. If you have multiple torches, test them to see which suits you best.

Preparation of plastic

Very important: remove all dirt! Any remaining dirt will melt into the plastic and become impossible to clean. Before starting, wash the ramp thoroughly, either in the dishwasher (at a low temperature and without the drying cycle) or by hand.

Remove all switches, extra plastics, flashers, and protectors so the ramp is completely free. Make it a habit to clean ramps thoroughly to remove wax, Novus, and other cleaning product residues.

Ensure you have a clean, flat surface to lay the ramp on while it cools. Dirt can ruin the finish, and the ramp needs to stay flat to avoid bending while flexible.

Flame-polishing with a torch

Once your ramp is clean, it’s time to begin. The most important thing is not to overheat the ramp! You’ll need to get used to touching the ramp with the flame, that’s the goal.

Always keep the flame moving! Never hold it on one spot for more than 1–2 seconds. On the TOP DVD, they pass the flame once or twice over the ramp from end to end. I prefer working in small sections. You’ll need to practice to find your preferred method.

If working in sections, allow the ramp to cool between passes. The speed is hard to describe, you’ll need to experiment or watch someone do it. But we’re talking seconds, not minutes. Flame polishing the long entire Cirqus Voltaire ramp took about 10 seconds.

Holding the flame too long in one spot will burn the plastic. This looks like small air bubbles that suddenly appear. The surface becomes rough and can’t be smoothed again. If you see bubbles, stop immediately! Your ramp is damaged. Don’t try again after cooling, it will burn instantly. (You can use 2000 grit sandpaper to remove them.)

Another beginner mistake is going over the ramp too many times. Even if the flame is moving, the ramp can overheat, become flexible, and bend under its own weight. Once cooled down, it retains that shape. I even had the texture of my glove imprinted on a ramp once!

But when done correctly, haze disappears and the plastic becomes smooth and shiny. It’s best to go over the ramp only once or twice. The ramp should stay cool enough to hold by hand. I don’t wear gloves anymore. If it’s too hot for my hand, it’s too hot for the ramp.

If you feel heat, set the ramp aside to cool. Plastic cools slowly. Wait at least 10–15 minutes. Watch out for ramp edges, they’re upright and closer to the heat, so they become flexible first. You may not notice this while focusing on the center where the haze is.

Deep scratches may not disappear completely. Use plastic polish like Novus 3 first to reduce them, then flame polish as a finishing touch. Some people use 2000 grit wet sandpaper to reduce deep scratches. I’ve tried this. It works somewhat, but don’t overdo it or you’ll create haze that’s hard to remove. Use sandpaper only on deep trails, at your own risk.

When polishing outer ramp sections, avoid decals and wires! The most important tip: keep the flame moving! Never stop. If you want to inspect your progress, move the flame away first. Concentrating while holding the flame still is risky. Always keep it moving, moving, moving!

Flame-polishing using a solder-iron on gas

A friend of mine uses a gas-powered soldering iron. By removing the metal tip (normally used for soldering), you can expose the flame. It produces a small flame, which he says is ideal for ramps with tight bends. This method works well, although the flame is a bit small. Read below for my preferred and safer method of flame polishing.

Flame-polishing using a paint stripper

UPDATE: DO NOT USE THIS METHOD! It is too dangerous. I’m keeping this section here for reference only, as I experimented with it. Please read below for a safer flame polishing method.

I also tested a paint stripper to flame polish. So technically, polishing without an actual flame, since it’s the heat that matters. My paint stripper has two settings:

• 1: 300 degrees C, 240 liters of air per minute
• 2: 500 degrees C, 400 liters of air per minute

Even after aiming it at the same spot for 30 seconds on setting 1, the ramp didn’t get warm enough to become flexible or burn. But it also didn’t have much effect. If you want to try this method without taking too much risk, start with setting 1.

Setting 2 is warm enough but dangerous. After just 5 to 10 seconds aimed at the same spot, the ramp started to burn! Even after 5 seconds, the ramp became too flexible. The effect was impressive though, haze disappeared very well. With enough practice, you might get good results this way too.

Personally, I prefer using a torch. With a hot paint stripper, you have to work very fast and be extremely careful to keep the airflow moving. That’s difficult to do. When using a flame, you can see it and know exactly where the heat is. The heat is also localized to where the flame is pointed.

With hot air, you don’t see it, and it blows across the entire ramp. So even if you’re working on one spot, another part of the ramp is already heating up, increasing the risk of burning the plastic. If you only want to treat small spots on the ramp, the paint stripper can work well. Let it heat up, then aim it for 2–3 seconds at a hazy area. Still not clear? Let the ramp cool down thoroughly and try again later.

A safe method of flamepolishing

After experimenting with different flame sizes—both large and small, I’ve finally found a relatively safe way to flame polish. It’s not 100 percent risk-free (nothing involving fire ever is), but it’s the easiest method I’ve discovered that gives great results with minimal danger. Anyone should be able to do this.

When I first experimented with different flame types, I assumed bigger was better. The TOP DVDs show a very large flame, which requires you to work quickly and let the ramp cool off. My torch, shown in the pictures above, also produces a fairly large flame.

But a friend once told me he uses a small butane-powered soldering iron. That inspired me to try smaller flames and see how they perform.

My preferred tool for safe flame polishing is now a creme brulee torch. My wife absolutely loves it when I borrow her kitchen tools for pinball maintenance! (Yes, I’m being sarcastic.)

I absolutely love this butane torch. I won’t flame polish ramps any other way anymore!

Here’s my current workflow:

1. Clean the ramp thoroughly. I usually start by putting it in the dishwasher on the lowest heat setting. Then I manually inspect it to ensure all dirt is removed. The ramp must be extremely clean.
2. Use 2000 grit wet sandpaper to reduce deep ball trails that are often present in the center of the ramp. You don’t need to remove them completely. Just sand them lightly. This will create haze, but don’t worry; flame polishing will eliminate it.
3. Clean the ramp again to remove any sanding residue and loose particles.
4. Begin flame polishing! The small flame keeps the heat localized. Just keep the flame moving slowly. You don’t have to worry about other parts heating up and melting—only the area you’re pointing at. This is a major advantage over the larger, hotter methods described above.

I usually go over the ramp once on the front side, then lay it down and let it cool for a minute or more. Then I polish the bottom and outer side sections. Again, I let it cool. Then I do the top and inner parts. I repeat this process as needed.

Each time, you’ll notice the ramp looks better and better, and you can gradually remove the deep ball trail in the center. Just make sure to keep the flame moving and allow the ramp to cool completely after each pass.

The small flame from this butane crème brûlée torch is hot enough to melt the plastic, but small enough not to damage surrounding areas. I don’t even need to remove decals or switches and their wiring. Just be careful not to point the flame directly at them.

Pictures of flame polishing

Before	After
	This picture shows the result best: the top side is already done until about 3 inch above my hand.

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