Behind the scenes in building the copper sign.

Honestly, I can't help you directly with you "spout" pouring method. I can only give you a layman's view. With that being said, I'd say that you are correct in that the molten copper cooled too quickly once it hit the sand where the letters were cast. How you raise the temperature of the sand to a point where it will not impede the flow of the copper as you pour is beyond my knowledge. I do know that in later pours that you also included another spout for air to escape. I do not know if this has anything to do with that premature cooling (by not having an escape path for the superheated air). My other thought is that you got it "air-locked" and once the backpressure built up enough the weight of the copper couldn't overcome it and backed up. I also wonder if maybe having "channels" between each of the letters would have allowed for better flow because the space between the top of the sand where the letters were imprinted and the sand mold with spout had such little clearance between the two as to prevent good flow. This is my laypersons two cents. I think that the most critical of my thoughts though is to keep the sand in both halves as hot as possible to promote flow.

Really what? First time? Yep, really. I melted a couple very small batches testing and then did the sign.