The furnace GUI won't show the decreasing level of fire if coal blocks are used as the fuel source.
Comments 4
Disproven in 1.10.2. It might be that people don't expect it to take so long, but coal blocks are a massively energy-dense fuel, so it might appear that the flame isn't going down even though it actually is.
Is this still a concern in the current Minecraft version? If so, please update the affected versions in order to best aid Mojang ensuring bugs are still valid in the latest releases/pre-releases. If this has been done, we can reopen the issue.
Keep in mind that the "Resolved"-Status on this ticket just means "Answered", and that we are waiting for further information on whether this issue still exists or not. We will reopen it as soon as the requested information has been delivered.