help me work out what my kitchen sink is made of and how to clean pleeeease

[mad4mybaby]

ok another cleaning Q from me. Live in newe build house and kitchen sink is black. When you knock it it sounds solid (not cheap plastic) no idea how to get it looking like it should. I believe it is quite a matt finish but looks so drab and dirty. Have tried soaking bleach and kitchen sprays etc. Any ideas?

I have a black Astracast sink - it's made of composite. I find as it's black it soon builds up with visable limescale, so I blitz once a month with 'limelite gel' (from sainsburys or other supermarket) - it gets rid of all the scale and brings it up like new.