Glass tile has truly captured the hearts of consumers in both the residential and commercial marketplaces, making it important for tile installers to understand how to avoid trowel ridges and marks that are visible through translucent glass tile.
Do you know the proper technique?
Let's explore how this is done with the help of Mark Heinlein CTI #1112, National Tile Contractors Association Training Director and Technical Trainer / Presenter, and CTEF Evaluator.
This Glass Tile Situation
Mark received several photos (some of which you see in this article) which document issues with a translucent glass backsplash installation project. The tile is a mesh-mounted 2" x 4" clear glass tile.
The images capture the following situations:
- Mesh that is visible from the sides of the installed tile
- Trowel marks that you can see through the installed tile
It appears that a “V” notch trowel (not the best choice) was used for the installation. Also, the installation hasn't yet been grouted.
Mark's Visual Analysis
Based on the photos, Mark agreed that, especially when viewing the installation from an angle, the troweled, uncollapsed ridges of mortar in the grout joints are indeed visible through the translucent glass.
He offered the following recommendations for this particular already-installed situation.
Match the color of the grout to the mortar
Since the installation hasn't yet been grouted, he suggests that it might be possible to lessen the effects of the visible ridges by using a grout that closely matches the color of the mortar.
Some grout manufacturers make mortar colorants that may be mixed with the mortar prior to installing the tile to ensure that the mortar color will match the grout color.
Carefully remove the visible ridges
In addition, it might be possible to lessen the effects of the ridges in the grout joints by using a dulled putty knife or grout saw to remove the visible ridges. It is extremely important that the installer be very careful not to chip the glass tiles or create other divots or scratches in the mortar which could remain visible through the glass.
The Best Solution for Avoiding Visible Trowel Ridges Through Translucent Glass
However, the better solution for installations with translucent glass is to do it right the first time using the following procedure.
These steps will help achieve uniform mortar coverage and ensure no mortar ridges are visible through the tile.
1 - Select a bright white thin-set designed to bond glass tile.
2 - Mix the thin-set per the manufacturer’s instructions.
3 - Select the proper notched trowel to achieve minimum coverage (100% coverage preferred) under translucent glass tile.
4 - Apply the mortar in a straight line with the notched side of the trowel.
5 - After applying a small amount of mortar on the flat side of the trowel, move the trowel across the mortar ridges to create a smooth flat surface.
6 - Install the tile by beating it into place with a beating block or grout float.
Flattening mortar ridges with the flat side of the trowel
The technique of flattening the mortar ridges helps ensure that the problem you see in the photos does not occur. It also helps achieve the tile industry-required coverage behind each piece of tile. It is not difficult to do, but it does require some practice.
A square or "U" notched trowel works very well for gauging the correct amount of mortar then flattening the ridges.
You can view the Question Mark video from NTCA’s YouTube channel on flattening mortar ridges for glass tile for an example of how to perform this technique:
Additional Tiling Resources
These articles provide additional perspective on several of the best practices that Mark mentions:
>> Installing Large Format Glass Tile in a Shower: 10 Steps to Follow
>> Do You Ignore Grout Manufacturer Directions?
>> How to Correctly Trowel Mortar When Installing Tile?
>> The Tile Installation Experience with Scott Carothers at Coverings
Have You Encountered Unsightly Trowel Ridges or Marks Through Translucent Glass Tile?
If you've encountered those unsightly marks, what solutions have you tried to implement? Have you considered flattening the mortar ridges with the flat side of the trowel, as Mark Heinlein describes?
Let us know your thoughts in the comments box.
Note: We originally published this article on 04/10/2018, and have updated it.