I can attest to the fact that getting crisp letters like that in a casting is very difficult, even using bound sand.
Hats off to you for that casting quality !
Some have stated that vents are not needed on a sand mold, and in some cases that may be true if the sand is coarse enough to pass any air and gasses out of the mold cavity, but I always use vent holes in the high points of the mold cavity, in the cope (top part of the sand mold), since I did get air trapped in the high point of a mold one time, and it ruined the casting.
But as you mention, metal that flows up the vent holes is a good indication that the pour temperature was hot enough, especially when pouring iron.
If you get aluminum or a similar metal too hot (I generally pour aluminum at 1,350 F), then it tends to penetrate the sand and cause a very rough surface finish.
Looks like you nailed the pour temperature, ie: not too hot and not too cold.
Any idea what your pour temperature was?
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