I would seal the tile before grouting.
Applying sealer to marble tile pre grout.
Sealing the tile before grouting doesn t get you out of sealing it after grouting though.
If your tile is not glazed be extremely cautious when applying the sealant as it will absorb directly into the tile and will change the color and finish of the piece.
Apply your sealer to the lines and joints of the grout.
For the walls you ll have to spray on the sealer and wipe around with a paint brush or sponge to keep the tile and grout wet with sealer long enough to soak in.
Then wipe off all excess until completely dry.
Let it soak in for 2 5 minutes.
Marble sometimes gets circulary etches scrathed into its polished face with sanded grout.
Use an impregnating sealer.
Apply the sealer to the carrara marble tile and grout by creating a film of sealer.
Unlike a ceramic or porcelain tile floor it s not just the grout lines where sealing is critical but the entire surface.
To protect your tile properly seal it a second time after the grout cures.
The same process used to seal marble floors can also be used to keep a marble countertop sealed against stains.
Then wait 3 days minimum after grouting giving time for grout to cure and then seal the grout.
The process for sealing a marble floor is relatively easy and should take less than an hour with each application.
The spray on variety is the most common although some types can be applied with a sponge or brush.