If these "verrrry old newspapers" have monetary or sentimental value, sandwiching them between sheets of glass may be among the best ways to assure their eventual destruction.
Condensation between the glass sheets would soak directly into the paper, fostering mold and mildew. That may take only one episode when the glass becomes suddenly warmer on the inside than on the outside. For example, when you transport the frame in a hot car, then take it into an air conditioned room.
Personally, in retail framing I prefer to construct the framing with an air space between glazing and whatever is in the frame, in order to slow down the rate of temperature and humidity change inside the closed-up package. (A large volume of air takes longer to heat/cool than a small volume of air.)
Using acrylic, as Hugh suggested, is a good idea because it is a much better insulator than glass, and would not condense moisture so readily. Also, it has half the weight and 20 times the shatter-resistance of glass, which could be important if the frames are large. Also, a glass sandwich is risky; the papers could be shredded by broken glass on both sides.
In any case I suggest you take Hugh's advice and frame copies, not the real newspaper pages.
