Eileensfamily - Use a SLATE seal or stone seal.( I use Sovereign, Lithofin etc.) Give it as many coats as required before it starts to lie on surface and don't leave any on after 10 mins - wipe off! You wont see a great change straight away but after day you will tell by dropping a droplet of water on the surface - It will 'ball' up.
Even after sealing Fat splashes should be wiped up asap as they can soak into the surface. You can help protect further by putting a polish ( HG golvpolish or similar) onto the tiles. It is removable and easily touched up.
Timeless John.