A joint root condition in a groove weld in which weld metal does not extend through the joint thickness. See Figure 1-3. See also COMPLETE JOINT PENETRATION, COMPLETE JOINT PENETRATION WELD, PARTIAL JOINT PENETRATION WELD, and JOINT PENETRATION. Incomplete Penetration. Among the causes of incomplete penetration are improper joint preparation; using an electrode that is too large, using insufficient welding current, and excessive welding speed. To correct incomplete penetration: allow proper opening at bottom of weld; use electrodes of appropriate diameter in narrow groove; use sufficient welding current and proper welding speed; use a backup bar; chip or cut out the back of the joint and deposit a bead.