When doing metal work it is essential to understand and choose the correct welding technique for the job. Even if you are not doing the work yourself, understanding proper welding form allows you to evaluate the quality of work that is being done on your car. If the restoration shop does not apply the correct techniques then it should be a red flag that they are lacking in the necessary knowledge to do a good job.
The most common welding techniques used are MIG and TIG welding. In MIG, a steel wire is fed by a gun and this is the material that is added to make the weld. TIG, on the other hand, requires the operator to add material via a rod with one hand while heating the metal with a special torch in the other hand.
Instead of me laboring on the differences the following video does an excellent job of explaining MIG and TIG and their respective strengths and weaknesses. In addition there is excellent information on general body repair.
Pay particular attention between the 1:00 and 2:00 minute marks as very few body shops know or respect the dangers of doing MIG repairs mid panel.I have stared at more than one car in the sun and seen exactly what is warned about:
(If the video looks black just click on it and it will start)
There is a third technique and that is to Gas weld using a torch and welding rod. This is the most difficult technique, requires the most skill, and is the least forgiving to error. That said, it results in a seamless repair and is the technique that was used when the cars were made new.
We have chosen to Gas weld all of the body seams because it leaves the most perfect surface and minimizes the need for additional filler when finishing the panels.
Special thanks to Stacey David and Gearz Television for the video clip. Gearz is an excellent program with some very good technical segments. It is worth looking up on YouTube or on TV if your cable provider carries it.