If that is true, I messed up my ingot and have to buy a new one.
What do you think?
To cast the thinner ingots, you need to heat the mold hotter. Also,
lubrication of the mold surface is more important. Oil the thing,
then heat till the oil is smoking, and the mold considerably too hot
to touch. Another good surface lube, less smelly, is if you’ve got an
acetylene torch (any type). Use just a plain acetylene flame (block
the air inlets on an air/acetylene type torch), so you have a bright
yellow sooty flame. Use that to coat the inside surfaces of the mold
with a good layer of carbon. Either this, or the oil, (don’t use too
much. Just enough to make the surface slightly oily before heating
the mold) will help cut that surface tension. Then a hotter mold, and
if needed, slightly hotter metal (not too much. a hotter mold first,
then if that isn’t enough, increase the pouring temp slightly.) Also,
be sure the ingot mold is not such a perfect tight air tight fit
between the sides. You want a little trace of a misfit, a tiny bit of
gap, usually just from coarser machined surfaces, so that air can
fully escape as the metal enters. That trace of flashing one gets on
the edges or ends of an ingot because of those slight gaps may be
annoying, but they help get a more complete fill, especially on
smaller/thinner sizes of sheet and wire ingots.
By the way it should be mentioned that though the extra rolling of a
thicker ingot is work, the result is usually better quality metal.
Rolling and annealing and rolling give you more uniform and stronger
sheet. If your poured ingot is only slightly more than you’ll end up
with, you loose some of that benefit.