Can kamma be erased?

Question :(Unedited)

Hai Justinchoo,

i would like to know if bad karma could be reduced or may be erase? or maybe, convert these bad karmas to good karmas?

My comment: 

Hi Y...,

Thank you for asking me.

We may say that kamma works in mysterious ways, but surely it will take its course.  We shall not be able to know exactly how kamma works unless we have reached a very high level of mental (Mind) cultivation.  As lay persons we can only learn from the Buddha's expositions.  The Buddhist context of kamma is "volition" actions, meaning those actions we do on purpose with full knowledge and awareness.  There are various grades of kamma, from the very insignificant to the very serious.  The lower grades of kamma will have lesser effect, while the serious one will take precedent.  I don't think it is possible to convert bad kamma to good kamma.  Once action is done, it cannot be undone.  However lesser bad kamma may be overwhelmed by a surge of good kamma, that the former may not have the chance to fructify. As for the really serious kamma it is quite impossible to escape its retribution.  This is one of the reasons where we often witness good people suffering with no apparent reason.

We can use an analogy of the hour-glass.  All our actions are the sand in the hour-glass.  There is no escape, each one will take its turn to flow down.  However, some will just be hidden in the flow, escaping notice.

Hope this explains sufficiently.  Please come back if need be.