i Have used loads of different sealers for natural all giving different results there each to there own some bring out the colours more than others, i would not recommend sealers they just coat the surface, impregnators are the best.
Bal do a very good tile sealer and its pretty cheap soaks in well and wipes off easy.
lithofin and Fila are top quality impregnators and sealers you can't go wrong with there products, HG and Aquamix i'm not to fond off they darken light colours to much and dry like treacle.
Just remember to follow the instructions its normally leave for between 5 - 20 mins depending on product and re apply. Then do a test with water called the 30 second test. IF the water stays on the surface after 30 seconds they are fine.
Its a must that you clean all the natural stones before applying the impreg or sealer. I have tried a sponge roller, paint brush and jay cloths.
Jay cloth is about the best on large format tiles and a paint brush for natural mosaics.
Also use a decent quality grout a course grout can scratch the surface of some tiles. I Don't use mapei products i go with bal which have never failed or reacted. 1mm spacers if you can get them 2mm will be fine.
One last pointer is if you seal the tiles again after you have finished the job, it will change the colour of the grout, plus u need to make sure all the grout dust or haze has gone. I normally say to the customer do it once a year in a bathroom or when needed in heavy trafic area's.
If you leave the sealer to long use white spirits to clean excess off.
Hope this helps i have done loads of natural stone with great success
( make sure the rooms well ventilated or you will end up high as a kite)
