I have always sealed after but i have also done very little work with marble tiles esp dark colors esp on a floor.
Marble not sealed before grouting.
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.
I used this sealer and just put it in a spray bottle and sprayed three coats on the ungrouted tile.
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.
The grout joints are especially susceptible to staining so it is important that they get coated thoroughly.
If this is not done minute particles of grout will sit in the pores and result in a hazy surface appearance.
Sealed my tile before grouting to make sure they didn t stain i used tec power grout.
Use the broad edge of the brush to wipe up any excess.
This must be removed but careful what you use.
If the tile is dull after grouting then it is probably due to grout haze on the face of the tiles.
Do you polish the marble before sealing.
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.
The sealer seemed to do the trick.
Most grout haze removers will etch marble.
Dip the foam brush lightly into the marble sealer then run the thin edge of the brush along each of the grout lines.
Countertop specialty comment.
Then i used a grouting sponge to wipe off any excess.
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.
This is usually polished marble installed as larger slabs and not as individually cut tiles.
Let the sealer dry completely this usually takes two to four hours.
Before you consider sealing your tile keep in mind that there is marble that does not need to be sealed.
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.
I just installed marble tile in an entryway dark green with dark grout.