Just read the PDF description and some top info there,worth reading HOWEVER,it dosent work exactly that way in the real world as when they say it's hard to burn through or "strike through" believe me as someone who does this on a regular basis weekly it's very EASY to burn through.leave it on a patch for more than a few seconds and that's generally it.although I mainly work on fresh paint,it's really easy to do so keep it wet and you'll be a lot safer.I tend to keep an old 2 litre water bottle full with a hole made in the top of the lid to squeeze onto the metalwork when your using it.you'll soon get used to it and the machine you've bought looks the dogs to be fair.good luck ! !!!