Quote Originally Posted by Crusty View Post
. . . . Apparently you need a costly bubbler rig to achieve significant degassing. I did use a smallish tapered sprue along with the Campbell pouring basin design which eliminates gulps of air while filling and there weren't any voids that I saw during machining.
Years ago I remember using some cheap tablets to degas. Can't remember the chemical but I think chlorine was part of the mix. Supposedly, it combined with the hydrogen gas in the aluminum to out-gas hydrochloride or sumptin equally as toxic. The "bubbler" was just a simple, small, steel cup with holes I drilled in it and welded to the end of a steel rod. Drop the tablet on top of the molten aluminum and then plunge the cup and tablet to the bottom of the crucible holding it there while it dissolved creating a lot of gas that would bubble up to the top carrying impurities with it.