I think before you even buy time for the blast furnace it should make a suggestion to put your Coal IN LAST,in case you get carried away and end up with 200 ore stuck in the melting pot (Like this smart man)... the only thing you can do is relog and lose it all. For ironmen this could be a big setback, especially since they have to grind everything themselves. Im just trying to save someone from my misfortune.
TL;DR Woops, I lost ores..warn peeps.