Non-Destructive Lifting Of Stamps Cancelled With Ink Pen

Can any of our members help me? I have some revenue documents where I would like to lift the stamp in order to examine the paper type (this isn't possible by looking from the front). Unfortunately, the stamps are all cancelled in black ink. Lifting them traditionally (e.g. sweat box or steaming) makes the ink run and ruins both the stamp and the document. I'm rapidly running out of expendable documents, and it is starting to get expensive!

Are there any other methods which you could recommend? Thanks in advance.

I have some super safe stamp lift fluid. when used I have been happy with the results. I have not used it enough to know for sure on pen cancels. My suggestion would be to try it on something that has already run and see how it goes.