Soldering nonnoble alloys. 
Successful presoldering of nonnoble alloys is variable at best.  Under controlled conditions of joint gap distance, investing, and soldering, more than one third of the soldered joints are likely to fail.  Furthermore, the recorded strength of successful solder joints was inconsistent.  Improved heat application and controlled oxidation are required.  Until new materials and/or techniques are developed, the soldering of nonnoble alloys prior to the application of porcelain is unwarranted.