If you seal the marble first then at least you have a better chance of using acid to remove any grout staining on the tiles cuz of the thin film of sealer between the acid and the marble.
Marble not sealed before grouting.
Because marble is a natural stone and will absorb color you need to seal them before you grout to prevent the grout from discoloring the tile.
If the tile is dull after grouting then it is probably due to grout haze on the face of the tiles.
If this is not done minute particles of grout will sit in the pores and result in a hazy surface appearance.
All natural stone tiles polished shiny honed matte or tumbled antiqued are porous therefore sealing before grouting is essential to fill these pores with protective sealer.
The grout joints are especially susceptible to staining so it is important that they get coated thoroughly.
Before you consider sealing your tile keep in mind that there is marble that does not need to be sealed.
Polished marble shouldn t need sealing before you apply grout but tumbled marble does it s so absorbent that the grout itself will stain it during the installation process unless you seal it.
I have always sealed after but i have also done very little work with marble tiles esp dark colors esp on a floor.
Then i used a grouting sponge to wipe off any excess.
Countertop specialty comment.
Sealed my tile before grouting to make sure they didn t stain i used tec power grout.
I just installed marble tile in an entryway dark green with dark grout.
The sealer seemed to do the trick.
I used this sealer and just put it in a spray bottle and sprayed three coats on the ungrouted tile.
Sealing the tiles and grout will significantly extend the life of your marble shower as well as making it much easier to clean and maintain.
Let the sealer dry completely this usually takes two to four hours.
This must be removed but careful what you use.
All natural stone should be sealed prior to and after grouting you may end up with grout haze or staining to the surface of your tiles your fixer should already know the potential problems.
Use the broad edge of the brush to wipe up any excess.
Most grout haze removers will etch marble.
Do you polish the marble before sealing.
I am using a grout from a store i never used before and they told me to seal the marble before grouting because the grout might stain the tile.