The backing is defined as material placed at the root of a weld joint for the purpose of supporting molten weld metal. Its function is to facilitate complete joint penetration. Permanent backing is usually made from a base metal similar to that being welded and, as the name implies, becomes a permanent part of the joint because it is fused to the root of the weld and is not easy to remove — See: Backing in welding for more information. Temporary backing may be made from copper or a ceramic substance that do not become fused to the root and are easily … Continue reading Backing vs Retainer in Welding