Why can't I cook sand in Minecraft Pocket Edition to make a glass?

I can not cook sand in Minecraft Pocket Edition.

How do I make glass?

1 Answer

You make glass by putting sand in the top box of a furnace and fuel (e.g. coal, charcoal, wood, etc) in the bottom box. Wait a few seconds for it to smelt, and glass will come out in the box on the right.

If you are doing this correctly, I don't know why it isn't working. If you could give more info it would be easier to help.