How to reduce the capacitance in transformer?

I need to reduce the capacitance between the primary and the secondary in a 50 Hz transformer design using two chambers bobbin, to improve the insulation, and decoupling the circuit from the line.
Is necessary to add a coppers lamina, and where?

Thanks in advance

PD: Please recommend me a book about transformers design and implementation

The usual trick is to encolse both primary and secondary turns in separate copper shields (making sure that they do not form a shorted turn) and ground the shields.

What means enclose?
Cover all the superficies, or put a copper foil over the primary and the secondary.
Remember that I using two sectors (or two chambers Bobbin), in one this primary and the other of alongside this the secondary one.

Thank you

Here is a very good article:

www.itee.uq.edu.au/~elec4301/isolat~1.pdf

That link is dead now. Here is an html copy.

http://molasar.blackmagic.com/ses/br...solatrans.html