Copyright Goodheart-Willcox Co., Inc. 150 Gas Tungsten Arc Welding Handbook Concave weld. A concave weld is formed when insuffi cient metal is added to the molten pool. How to correct: • Deposit more material into the pool with each application of the fi ller metal. Convex weld. A weld that has a high crown. How to correct: • Deposit less metal into the pool with each application of the fi ller metal. Craters. Formed when weld metal shrinks below the full cross section of the weld. How to correct: • Do not stop welding at the end of the joint (use tabs). • Using the same travel torch angle, move the torch back on the full cross section before stopping. Cracks. Occur in fi llet welds just as they do in groove welds. How to correct: • Use suggestions for groove weld cracks.