Bone products which gives off negative vibration will affect your practice, unless you have the ablity to cleanse it with your own power. Just like a peacock absorbing poison, if not you will face hindrance in your practise. I guessed it could be possible to get possessed by the spirit in worst case.
I have a question here, let say the bone products that we use will give off negative vibration, do we really need to have the ability to cleanse it with our own power? The purpose of us using a mala is just to recite holy mantra of each enlightened beings, if you said the person who use this mala could be possible to get possesed by spirit, does it mean that the holy mantras don't have the power to avoid the negative influences? If a holy mantra doesn't have the power to even conquer the negative energy from a dead person, then what is the purpose of reciting a mantra? Please explain more as I'm getting confused now.
Yes, it is possible to get possesed when you are much weaker than the spirit, even if you had HYT empowerment, it does not mean that you are invincible. At least, you are armed with holy mantra and it can act as deterrent to malicious forces. This is a lesson learnt and I have seen things happening on several ocassions to relate that we (the laymans) are not almightly.
You will know by yourself better if you are weak. There are people doing self initations daily, protector saddhana, guru puja etc. daily. In a way, you will develope stronger and should have some at least some gurantee, when cleansing the bone mala yourself. To be insure yourself, you should ask your Guru if you are up to the level where you can do cleansing by youself.
Another point is that it is not really neccesary to have the bone mala, unless you are going for some special HYT retreat like Heruka, which may require real kapala. If you really want to use a human bone mala, please get your Guru to verify and cleanse the mala before use. Lastly, please cover with cloth bag when you use the human bone mala to pray, as it is to wrathful to be seen by the sentinent beings from the other dimension.
A highly blessed kapala or bone mala of highly attained practioner has some electrifying tingling senastion, which you feel very comfortable holding it. Usually the kapala have some sanskrit wordings of seed syllables on it.