Asphalt is made by the Blend-O-Matic, not the Solidifier. They're often confused, I suppose because they're both roundish grey metal things, but they're pretty different.I mean if IIRC solidifier makes asphalt so it's not totally out of hat.
Notably, Solidifier is dropped by King Slime, so it's normally obtained quite early in progression, while Blend-O-Matic is bought from the Steampunker, making it a post-mech boss item in normal worlds. (You can get it early on a CelebrationMK10 or Get Fixed Boi world.)