Put the summary of the bug you're having here

*What I expected to happen was...
That I could use the furnace

*What actually happened was...
I put sand in the furnace and then it would not let me put coal in the furnace then it would not give me the sand back unless I destroyed the furnace.

Steps to Reproduce:
1. Put sand in the furnace
2. ...then try to put coal in the furnace and you will on be able to.
3. ...then try to take the sand out and you will not be able to unless you destroy the furnace.