12. (a) In which hand is the welding torch held in aluminum work?
(b) In which, the “filler-rod”?
(c) The puddle stick?
13. (a) What materials are used to “back-up” aluminum work for preheating?
(b) Describe fully how aluminum is “backed-up” previous to preheating, in order to prevent the collapse of metal while welding.
14. (a) How quick does the heavy coating or aluminum oxide form on a clean hot piece of aluminum?
(b) Will the metal flow together when this oxide is present?
(c) How is it overcome?
15. (a) Is it advisable to weld aluminum from one side only or from both sides?
(b) Why?