1.14 saw the addition of smokers and blast furnaces to Minecraft. Their main purpose is to speed up the smelting of certain items. Smokers are for smelting food, and blast furnaces are for non-food items. Right?
Apparently, I was wrong.
I just tried to smelt sand to make it into glass. It wasn't a food item, and I put it in the blast furnace. It wasn't accepted.
I then thought maybe that it was considered a smoker item, not a blast furnace item. So I decided to put it into the smoker and test it.
It also wasn't accepted.
Therefore, it must be that some items cannot be smelted in either special furnace, and must be smelted using the normal furnace.
I now know that Sand → Glass is a recipe that must be used in a regular furnace, and not a smoker/blast furnace.
The Minecraft Wiki doesn't provide a full list of these items, only saying that "some items" are not compatible with either furnace.
To save me from having to enter the maintenance area of my Smoker & Blast Furnace Super Smelter™ and pluck out items that don't belong, could someone provide a full list of these items?
Best Answer
Items that may be used in a smoker
Raw food items only. Notable exception is Chorus Fruit; although it is edible, it cannot be cooked in a smoker because its smelting product (Popped Chorus Fruit) is not edible.
Items that may be used in a blast furnace
Ores of any type, Chain/Iron/Gold armor and tools, and Ancient debris only. Note that block types cannot be smelted in a blast furnace—you will only get ore items from the blast furnace (nuggets, iron, etc).
Items that may be only used in a furnace
The furnace may be used to smelt any of the items in the other sections. However, ONLY the furnace may be used to smelt these items:
Sources