Can you remove properties from weapons?

[Peter....@ntlworld.com]

Hi,

I have used Synthesis to put some extra properties on a weapon but now
I want to remove them.
Smithery just seems to duplicate the properties, so how do I remove
them?

I am fighting Super Blair and just can't survive so I want to remove
weaker properties from my weapons and then make them stronger
(certainly need more defense).

Any ideas?