preferable to weld cast iron without the use of a flux, and in any event
the smaller the quantity used the better the result should be. Flux should
not be added just before the completion of the work because the heat will
not have time to drive the added elements out of the metal or to
incorporate them with the metal properly.

Aluminum should never be welded without using a flux because of the oxide
formed. This oxide, called alumina, does not melt until a heat of 5,000
Fahrenheit is reached, four times the heat needed to melt the aluminum
itself. It is necessary that this oxide be broken down or dissolved so that
the aluminum may have a chance to flow together. Copper is another metal
that requires a flux because of its rapid oxidation under heat.

While the flux is often thrown or sprinkled along the break while welding,
much better results will be obtained by dipping the hot end of the welding
rod into the flux whenever the work needs it. Sufficient powder will stick
on the end of the rod for all purposes, and with some fluxes too much will
adhere. Care should always be used to avoid the application of excessive
flux, as this is usually worse than using too little.


SUPPLIES AND FIXTURES

_Goggles._--The oxy-acetylene torch should not be used without the
protection to the eyes afforded by goggles. These not only relieve
unnecessary strain, but make it much easier to watch the exact progress of
the work with the molten metal. The difficulty of protecting the sight
while welding is even greater than when cutting metal with the torch.

Acetylene gives a light which is nearest to sunlight of any artificial