How to flamepolish plastics to remove scratches and dull hazy spots

This article describes how to flame-polish plastic ramps of a pinball machine. It is a technique to remove scratches out of acrylic plastic, to make the parts look as new again. By quickly heating the plastic with a hot flame the surface of plastic will melt and become smooth. I hope you will enjoy this flamepolishing tutorial.

Warning: the author of this page can not be held responsible in any way for any damage you have when trying this ! Use at your own risk !
I just want to make this clear, don't complain to me if you melted your precious ramp ! Flame polishing is dangerous !

Introduction to flame polishing

Whirlwind new playfield

Everyone who has looked closely at pinball machine flyers will have noticed: brand new plastic ramps are shiny and very transparent. On photographs you have to look closely where the ramps are, sometimes you hardly see them !
Compare this to a used pinball machine and you notice the ramps now much more.. they're clouded, scratched and you can hardly see anything through them.

There is a way however to make used ramps look 'as new' again. This is done by flame-polishing. By heating the acrylic plastic, the top surface will melt and become smooth again. Small imperfections and haze are gone. Sounds easy, doesn't it ?

If you want to see how flame polishing is done, buy the 'This Old Pinball' dvd 4 (Indiana Jones). If you are interested in flame polishing, please buy the tape. It is a very small investment compared to buying a new ramp. This technique is something you have to see being done, before you should try it.. especially if you don't have a lot of ramps to test on.

I had heard for more than a year about this, but only recently started to practice with it and actually do it on my machines.
I had bought a Theatre of Magic. One broken ramp I replaced with a brand new one. The other ramp I wanted to look as good as possible, because a nice shiny game with one new ramp and one old ramp just doesn't look right. Flame-polishing was the only solution, and it had to be done right. I must say it worked very well, as it's very difficult to tell which is the 'old' polished ramp and which is the brand new one..

I'm certainly no master in flame-polishing. I still have to learn a lot and experiment more. However I have discovered some things already so this way I want to tell people what can go wrong, so they can learn from my mistakes.

Again a warning: flame-polishing is not something anyone can do ! You take a risk, if you're not careful you can destroy 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's not visible..

Conditions for flamepolishing

Flame-polishing is done on translucent ramps of pinball machines from the 90ies. On non-translucent ramps (ie the black ones used on games in the 80ies) it'll have no effect (there's no haze) and scratches can better be removed using a plastic polish.

It's always possible some ramps are made from a different type of plastic, which may burn or melt at other temperatures, so be careful if you have a ramp which looks or feels different. This technique works best on acrylic plastic.

burnt whitewater whirlpool ramp The small blue ramp on Bally's Strange Science is also one which you should not try, its plastic is really too thin.
And as you can see in the picture: also be very careful around the thin part of the Whitewater whirlpool ramp !!!!!

Playfield windows like Creature of the Black Lagoon, Popeye, Black Hole and Haunted House can be flamepolished too but I have not tried this myself.

I also did not test this on ramps which have been glued or repaired with resin/epoxy. Be careful as these products may react to heat.

This technique can be used to remove small scratches and haze. It is not intended to repair holes, breaks or thick scratches. Yellowed plastics will stay yellow.

You can use this not only on ramps but also on other translucent plastics and bumper caps. But be careful as they may burn very fast.

Required tools to flame polish

tools for flamepolishing

You need a torch. There are several types, I'm no specialist.. I use a small one, bigger ones may be too hot.

If yo have multiple torches available you may test with all of them and see what type suits you best.

Preparation of plastic

Very important: remove all dirt ! If there's still some dirt present, it will melt into the plastic and it's impossible to ever get the ramp clean !

So before you begin, put the ramp in the dishwasher (no drying cycle) or wash it by hand and clean well with water.

Also remove all switches, extra plastics, flashers, protectors so the plastic itself as free.

It's best to make it a habit to always clean a ramp to remove all leftovers of wax, novus and other cleaning products.

Make sure you have a clean spot to lay the ramp down so it can cool. You don't want any dirt getting in it, and the ramp needs to lay flat as it can bend when it's flexible.

Flame-polishing with a torch

Ok then, your ramp is clean, time to start. The most important to take care of is not to make the ramp too hot !

In the beginning you have to get used to touch the ramp with a flame, but that's the goal.. What you have to take care off is that you always keep the flame moving ! Never ever keep it pointed at the same spot for more than 1 or 2 seconds !

On the TOP tape they go once or twice over the ramp from beginning to the end. I prefer to work in small parts. You'll have to practice yourself. If you work in parts, make sure you let the ramp cool down in between for enough time.

How fast you should go is difficult to explain, therefor you have experiment or see someone do it. But we are talking about seconds and not minutes. The whole Cirqus Voltaire ramp was done in about 10 seconds.

burnt ramp

Keep the flame too long on one position (more than a few seconds) or go too long over the ramp, and the plastic will burn !

This burning looks like small air-bubbles which suddenly show up. The surface becomes rough and cannot be made smooth again !

If you see these air-bubbles show up then stop immediately ! Your ramp is damaged ! Don't try again when the ramp is cooled off because the air bubbles burn immediately when heated ! (you can use 2000 grit sandpaper to remove them)

Another mistake which you may do in the beginning is going too long over the ramp. You keep the flame moving but the ramp itself becomes too hot. Not only do you have the risk of air-bubbles, but the ramp will become too flexible and bend by its own weight. When it cools down it will stay in this shape. Once I even had the texture of my glove printed in the side of a ramp.

But let me tell what happens if you do it right. Haze just disappears and the plastic becomes smooth and shiny again.

So it's best to go only once or twice over a ramp. The ramp must stay cool enough so you can hold it by hand. I don't wear a glove anymore: too hot for my hand is too hot for the ramp ! If you start to feel the heat, then put the ramp aside to let it cool down. Plastic cools slowly, don't think after a minute you can start again. I usually let it cool for 10 to 15 minutes.

Also watch out for the edges of the ramp, as these are upright they're closer to the heat and first to become flexible. Most of the time you don't notice it as you're concentrating on the middle part of the ramp. This is another reason not to go too much over the ramp, but only a few times and then let it cool before you try again.

Deep scratches in the middle of the ramp may not go away totally. Therefor you may have to use a plastic polish like Novus 3 first to reduce them as much as possible, and use flame polishing as the finishing touch.
Some people make scratches less deep by going over it with 2000 grit wet sandpaper. I tried this and it works a bit, but don't go over it with sandpaper too long or you'll make a haze that you can't get totally out ! So only use sandpaper on the small deep trail in the middle of ramps, on your own risk.

If you're doing the outside parts of the ramp, be careful not to get near decals and wires !

The most important tip I can give you: keep the flame moving ! Never stop. If you want to watch closely how it's going - put the flame away before you look. Because if you concentrate to watch how it's going, you keep your hand still. Always keep the flame moving. Moving, moving, moving !

Flame-polishing using a solder-iron on gas

A friend of mine uses a soldering-iron on gas. If you remove the metal tip (used for soldering) you can use the flame. It has a small flame, he says it's easy to do ramps which have small bends.
This is a good way, although the flame is a bit small. Read below for my safe method of flamepolishing.

Flame-polishing using a paint stripper

UPDATE: DO NOT DO THIS ! it is too dangerous. I keep this text here for reference as I experimented with it but you should not attempt it. Read below for a safe method of flamepolishing.

I also tested a paint stripper to flame-polish (so flame polishing without the flame part), as it's the heat you need:
My paintstripper has 2 positions, position 1 is the safest.

  • 1: 300 Celsius, 240 litre air/minute
  • 2: 500 Celsius, 400 litre air/minute

Even after aiming it for 30 seconds at the same spot, the ramp did not get warm enough to become flexible or burn. But it did not have a lot of effect.

If you want to try it without taking a risk then start with this.

Position 2 is warm enough but dangerous to use. After 5 to 10 seconds aiming at the same spot the ramp started to burn ! Even after 5 seconds the ramp became too flexible. The effect was very good though, haze disappeared very well.

If you practice enough you may get good results this way too.

Personally I prefer to use a torch. With a hot paintstripper you have to work very fast and really take care to keep the airflow moving. This is difficult to do. If you're using a flame, you see it and know where the heat is. The heat also is local to where the flame is positioned. When you're using hot air, you don't see it, and it blows trough the whole ramp. So if you're working at one spot, a bit further the ramp is also becoming hot already, which increases the risk to burn the plastic.

Only if you want to do some spots on the ramp you can use the paintstripper well. Let it heat and aim it 2-3 seconds on a hazy spot. Still not gone totally ? Let the ramp cool down long enough and try later again.

A safe method of flamepolishing

After experimenting a bit with different flames, larger and smaller, I have finally come up with a safe way of flamepolishing. It's not 100 percent safe (as nothing that involves fire can be), but it is the most easy method I have found which gives the best results with the least risk. Anyone should be able to do this.

When I experimented with different types of flames, I usually thought that bigger was better. The TOP tapes show a very large flame (and you have to work very quickly and let the ramp cool off). My torch, in the pictures above, also gives a pretty big flame. But a friend once told me he uses a small soldering iron which works on butane gas. So I wanted to experiment with small flames and see what it gave.

My preferred tool for flamepolishing plastics in a safe way now is a creme-brulee torch. My wife absolutely loves it when I used her kitchen utensils when working on pinball machines ! Yes I'm being sarcastic.
In case you're interested to know the specific model, it's a Typhoon Retro Revolution Creme Brulee Torch, which works on butane gas.
I absolutely love this butane torch. I will not flamepolish ramps any other way anymore !

Typhoon retro revolution creme brulee torch

My workflow now is:
1/ clean the ramp thorough. I usually put it in the dishwasher (on lowest heat setting) first.
Then I manually check that all dirt is removed. The ramp must be very very clean.
2/ I use 2000 grit sandpaper (wet) to remove the deep balltrails that usually are present in the middle of the ramp.
You don't need to get them out completely, just sand them a bit. This will haze the surface of the ramp but don't worry, as flamepolishing will remove this haze. 3/ Clean the ramp again to remove dirt and lose particles from sanding. 4/ Start flamepolishing !
The flame is small enough to keep the heat very local. Just keep the flame moving (slowly). You do not have to worry that other parts heat up and melt other than where you are pointing the flame towards. This is a big advantage compared to the other methods described above which use large flames and more heat !!
Just move slowly over the whole ramp. Usually I go over the ramp once, front side. Lay it down and let it cool off for a minute (or more).
Then I flamepolish the bottom and outside side parts of the ramp. Again, lay it down, let it cool off..
Time to do the top/inside part again. Lay it down, let it cool off.
Repeat this as long as it is needed. Each time you'll notice the ramp gets better and better, and you can get the deep balltrail out in the middle. Just make sure you keep the flame moving and let the ramp cool off once you've been over it completely.

The small flame of this butane creme brulee torch is hot enough to melt the plastic, but small enough not to damage other parts. I even don't have to remove decals or switches and their wiring, just make sure you don't point the flame directly on them.

If you don't dare to flamepolish your ramps yourself and live in Belgium (or nearby and want to visit me) then I can flamepolish your ramps. Contact me for details.

Pictures of flame polishing

theatre of magic ramp before flamepolishing theatre of magic ramp after flamepolishing
cirqus voltaire ramp before flamepolishing cirqus voltaire ramp after flamepolishing
ramp during flamepolishing This picture shows the result best:
the top side is already done
until about 3 inch above my hand.

There are also professional tools available for frame polishing. Check for more information.