Bubbles in MIG weld

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I have been MIG welding some new sheetmetal to old metal on a classic car.  Sometimes at the end of a weld, as soon as I let off the button, a bubble expands a little on the weld.  Sometimes it may pop, but if I grind into it, it is hollow.  Do you think this is a contamination problem or shielding gas problem.  I think I have had a problem with my MIG gun not flowing enough volume of gas in the past.  ThanksMark
Reply:That little volcano that rises and erupts at the end of the bead is fairly typical of a shielding gas problem. Of course contamination is one of the culprits that helps generate the gases that are coming out but that is generally dealt with by the heat, agents in the wire and shielding gas. You might make sure you don't have extreme contamination, like paint or oils but I'd focus on the shielding gas flows.
Reply:At least with flux core wire, I found that I had much less trouble with volanoes at the end of a bead if I let go of the trigger while moving the gun in the same direction as the weld, rather than lifting it up.  I don't (yet) have any solid wire experience, so I'm not sure if this would help in your case.
Reply:You need to hold the shielding gas on the weld momentarily after finishing with the weld so it can cool some.
Reply:Originally Posted by Vette GatorAt least with flux core wire, I found that I had much less trouble with volanoes at the end of a bead if I let go of the trigger while moving the gun in the same direction as the weld, rather than lifting it up.  I don't (yet) have any solid wire experience, so I'm not sure if this would help in your case.
Reply:Zapster is correct,  he is a honest King welder and continues to build a fortune in wealth/knowledge to pass to the next generation.  Thy Kingdom Come Thy will be done................