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I start with a hot air gun on maximum and a sharp scraper. The objective with the hot air is to soften the material, not to burn it off. If you see smoke, you've probably heated it too much. I follow that with white spirit or turpentine, a rag and a scraper. I avoid using a gas torch as it's too easy to start a fire, not necessarily where you're working so you don't see it at first. If you use one, keep a washing up bottle full of water and a fire extinguisher close by and stay aware (things you should do anyway). I also avoid as far as possible solvents beyond white spirit.
I find a hot air gun and a scraper work well on paint as well. For paint, I follow up with an angle grinder and abrasive.
Dr Classic Poland only use gas torches as a matter of portability. Never had a fire ever. It's a matter of technique. A hot air gun has just as much chance of causing a fire.
Last edited by Glyn M Ruck; 03-16-2024 at 06:24 PM.
Dr Classic Poland only use gas torches. Never had a fire ever.
One thing is a group of professionals working together, someone working alone at home is another. You can be using a torch on one side of a panel and have a fire start somewhere on the other side where the hot gases have penetrated. It happened to me (in the pre-MIG era) forty years ago when gas welding one of the panels behind the rear bumper. The first I understood something was happening was when I noticed light coming from where I didn't have an electric lamp. Fortunately, it wasn't a problem to extinguish.
The temperature of the air from a hot air gun is much easier to control and generally lower peak temperature than the flame from a gas torch. The total energy might be similar, but the gun produces a good volume of air spread over a wider area from a fan nozzle. As I said before, the objective should be to soften the material rather than burn it off. Of course, it's wise to be careful with the fan nozzle as it's easy to burn yourself if it touches any skin.
Dr Classic Poland only use gas torches. Never had a fire ever.
So they tell you Glyn but then again they are professionals.. As Pete says with a naked flame you might be working on one area and the fire creeps underneath the gunk and starts a fire in another area. Before you know it you will need to use the fire extinguisher. You are only trying to soften the stuff so a hot air gun in my opinion is so much safer.
My S Type did not have any underseal on the chassis but my Ford Anglia did and I spent ages with the hot air and scraper. Easy on the flat bits but on the curves and in the corners is a pain. Trying to use an angle grinder with a wire brush is a waste of time. The speed of the wire brush just heats up the underseal which becomes soft and clogs up the wire brush and is wiped all over the the part you are trying to remove it from. Been there and tried it not going back.
Glyn, I doubt a typical DIY hot air gun can deliver much over 500 C at the nozzle and all you have to do to turn it off completely is let go of the button. A hydrocarbon torch will be producing a jet a thousand C higher close to the nozzle. It may be fine for someone who works with it on a regular basis, but it's not for an occasional user like me or most of us.
Glyn, That's a serious professional device. I'm sure mine can't reach anywhere near that. It's way higher than required to melt paint and underseal. I emphasise melt as the smoke from burning the material isn't something I want to inhale and most often on cars we are working in relatively enclosed spaces. As you say, it is possible to start a fire, even with my gun, but it's not so likely to happen by accident.
To place in perspective the exhaust temp of an F1 car or racing motorcycle is about 1000 deg C. A ladies hairdryer absolute maximum temperature of 140 deg C.
I find the nice thing about a heat gun over a flame is the control of the heat gun.
A heat gun is very directional and can be controlled simply by moving it further or closer to the work, thus preventing over heating of the work.
Mine has a simple temperature control on the air intake.
It can be blocked off for maximum heat or opened so the heating elements can't reach their maximum temperature.
This is what mine looks like, the yellow dial is turned to open or close the vents.
I had many heat guns over the years that controlled the temp. electrically, but they didn't last very long, the crappy wiring in them cooked itself under heavy use.
This one I have now was quite a bit more expensive and it's standing up quite well.
I find the nice thing about a heat gun over a flame is the control of the heat gun.
A heat gun is very directional and can be controlled simply by moving it further or closer to the work, thus preventing over heating of the work.
Mine has a simple temperature control on the air intake.
It can be blocked off for maximum heat or opened so the heating elements can't reach their maximum temperature.
This is what mine looks like, the yellow dial is turned to open or close the vents.
I had many heat guns over the years that controlled the temp. electrically, but they didn't last very long, the crappy wiring in them cooked itself under heavy use.
This one I have now was quite a bit more expensive and it's standing up quite well.
The same could be said of a gas torch. It's infinitely controllable.
03-16-2024, 06:04 PM
