using Form

Hi all, 

i have been trying to work with the Form class (Graphics-Display Objects), to get a base 64 "form" (a String) representing the given Form.

I already now i can do the oposite, like this:

Form fromBinaryStream: (Base64MimeConverter mimeDecodeToBytes: aString readStream).

But i cannot find the right way to do it. Right now i am doing this:

(Base64MimeConverter mimeEncode: (aForm bits readStream)). 

Which, surprisingly, gives me a different form.

Any ideas what i am doing wrong here?