Each improvement uses 0.1 kg of the silver lump and raises the strength of the mine door by a fifth of the difference between current strength and maximum strength.
The following graph shows the decay of a silver mine door on deed over the course of about over a year. The Mine door has been repaired when the strength went below 2000a few times since.The decay has been about 30 28 strength per day on average over the first period of 192 days and 22 strength per day during the second whole period of 131 400 days.
[[File:Silver mine door decay.png|Decay of a Silver mine door]]