My earlier comment about sandblasting doesn't need a comment might have sounded a little harsh, but just think about it. Cast iron is a fairly soft material. Have you ever drilled or filed it? It drills almost like aluminum except it doesn't stick to the drill bit. Any hard abrasive like sand will obviously alter the surface texture.
Lye has a bad reputation it doesn't deserve. It dilutes easily and safely. It was and still is to some extent used in soap.
I use it very little in cleaning cast iron, because electrolysis is much easier and quicker and more complete.
But, without electrolysis, lye is the only way to go. In some cases, both used can get things done better.
