Best Grout for Glass Tile: Avoid Scratches, Haze and Cracking
On this page
The best grout for glass tile is one that will not scratch it: unsanded grout for joints under 1/8 inch, or an epoxy, urethane or fine-aggregate high-performance grout for wider joints and wet areas. Avoid standard sanded grout on glass, pick color knowing it may show through clear tile, and provide movement joints.
Key takeaways
- Quartz sand is about as hard as glass and will scratch glossy glass faces during floating and washing. Skip standard sanded grout.
- Glass absorbs no water, so cement grout cures slowly against it and hazes readily. Use low water and patience.
- Clear and translucent glass shows what is behind and beside it. Grout color affects the color of the tile edges, and setting mortar color affects the field.
- Glass expands more with heat than ceramic. Movement joints at perimeters and changes of plane matter more, not less.
- Coated, iridescent and metallic glass finishes can be damaged by abrasive pads and some cleaners. Read the tile maker's grouting instructions.
What makes glass tile different to grout
Glass tile, covered by ANSI A137.2, behaves differently from ceramic in four ways that affect grout. It is impervious, so it never draws water from the joint. It has a smooth, hard but scratchable surface. It is often translucent, so light passes through and picks up the color of whatever surrounds it. And it has a higher coefficient of thermal expansion than most ceramic and porcelain, so it moves more as temperature changes. Each of those properties points to a specific grouting decision.
Scratching: why sanded grout is the wrong default
Ordinary grout sand is mostly quartz, which sits at 7 on the Mohs hardness scale. Soda-lime glass is roughly 5.5. A quartz grain dragged under a float or a sponge will leave fine scratches on glossy glass, and those scratches catch light and hold haze. Matte or etched glass hides minor scratching better, but the haze still sits in the micro texture.
That is why the usual guidance for glass is unsanded grout in narrow joints, or a non-scratching alternative in wider joints:
- Epoxy grout (ANSI A118.3). Many glass tile makers recommend or prefer it, particularly in showers and pools. Fillers are fine and the cured grout is stain resistant.
- Urethane or other single-component premixed grouts. No sand in many formulas, consistent color, flexible. Check that the product lists glass tile as an approved use.
- Fine-aggregate high-performance cement grouts (ANSI A118.7). Some are marketed as glass-safe because the aggregate is very fine or rounded; test first.
Pro tip: To test any grout on glass, smear a little on a spare tile, scrub it gently with a damp grout sponge for 30 seconds, rinse and look at the surface at a low angle under a flashlight. Fine scratches show up as a dull streak pattern.
Grout choice by glass tile type
| Glass tile type | Typical joint | Recommended grout | Special caution |
|---|---|---|---|
| Clear or translucent mosaics (sheet mounted) | 1/16 to 1/8 in | Unsanded, epoxy, or approved premixed | Grout and mortar color show through; use white mortar unless told otherwise |
| Opaque painted-back or coated glass | 1/16 to 1/8 in | Unsanded or epoxy | Back coating must not be damaged; follow tile maker's mortar list |
| Iridescent or metallic finish | 1/16 to 1/8 in | Unsanded or premixed, tested | Abrasive pads and some cleaners can damage the coating |
| Frosted or matte glass | 1/16 to 1/8 in | Epoxy or premixed, tested for cleanup | Haze and pigment cling to textured surface |
| Larger glass subway and format tile | 1/16 to 1/8 in | Unsanded, epoxy, approved premixed | More thermal movement per tile; perimeter joints matter |
| Recycled glass with irregular edges | 1/8 to 3/16 in | Fine high-performance or epoxy | Wider joints need a grout rated for them, without coarse sand |
| Pool and submerged glass | Per maker | Epoxy or a pool-rated cement grout per tile maker | Water chemistry and cure time before filling are critical |
For pool and exterior use, see outdoor and pool grout. For sheet-mounted pieces of any material, the mosaic grout guide covers sheet handling and the high share of grout in small formats.
Color and translucency
With opaque ceramic tile, grout color only affects the joint. With clear or translucent glass, it also tints the tile edges, because light enters the face, travels sideways and exits colored by the joint. A dark grout around pale aqua glass mosaics can make the whole field look deeper and cooler; a white grout makes it brighter and more saturated. Neither is wrong, but the effect is bigger than people expect from a small sample.
The same principle applies to setting mortar. White mortar is standard under translucent glass, and many glass tile makers require it. Trowel ridges in gray mortar can show through clear glass as stripes, which is why glass is commonly set with a flat, fully collapsed bed or back-buttered tiles.
The grout color guide and color visualizer can help narrow choices before a physical sample.
Curing and haze on glass
Because glass absorbs nothing, cement grout against it stays plastic longer than against ceramic, and the excess water has to leave through the joint face. Setters adjust in three ways:
- Mix stiff. Use water at the low end of the TDS range. Extra water weakens the grout and causes shading that shows clearly next to bright glass.
- Wait longer before washing. Let the joint firm up until a light thumb press barely marks it. Washing early pulls grout out of narrow joints.
- Buff early. Glass shows every streak. Buff the light haze with dry microfiber as soon as it forms, before it hardens.
Cured cement haze on plain glass usually responds to a haze remover approved by the tile maker, but coated and iridescent finishes may not tolerate acids or abrasive pads. Epoxy residue needs an epoxy remover and is easiest to deal with in the first hour. See how to remove grout haze and how to apply epoxy grout.
Thermal movement and cracking
Glass moves more with temperature than ceramic tile. In a hot shower, behind a cooktop, on a sun-facing wall or in a pool, that movement is real and repeated. When the tile is trapped between rigid corners, the stress has to go somewhere: grout cracks along perimeter joints, or, in worse cases, glass tiles crack.
- Use flexible sealant, not grout, at every change of plane, inside corner and perimeter, and around fixtures, per TCNA EJ171. See caulk vs grout for movement joints.
- Use the setting mortar the glass maker specifies. Many require a highly polymer-modified or specific glass tile mortar, with full coverage.
- Behind ranges and near heat sources, follow the tile maker's clearance and temperature limits.
- A slightly more flexible grout, such as urethane or a high-polymer premixed product, can help in movement-prone areas, but it does not replace movement joints.
Picks by location
| Location | First choice | Also workable | Why |
|---|---|---|---|
| Kitchen backsplash | Epoxy or approved premixed | Unsanded, sealed | Grease and food stains; see backsplash grout |
| Shower walls | Epoxy | High-performance cement, sealed | Constant water, soap, heat cycling |
| Shower floor (glass mosaic) | Epoxy | Per tile maker | Standing water, cleaners, traffic |
| Bathroom accent band | Match surrounding grout if glass-safe | Unsanded | One grout simplifies the job if it suits both tiles |
| Fireplace surround | Per tile and grout maker heat limits | Unsanded | Heat exposure limits product choice |
Bottom line: Use non-scratching grout (unsanded under 1/8 inch, epoxy or approved premixed elsewhere), white mortar under translucent glass, a full-sheet color sample, and sealant at every corner and perimeter.
Frequently asked questions
Can you use sanded grout on glass tile?
Standard sanded grout is generally avoided because the quartz sand can scratch glossy glass. If joints are 1/8 inch or wider, use epoxy, urethane or a fine-aggregate grout approved for glass.
Is epoxy grout better for glass tile?
In wet areas and kitchens it is often the best choice, and many glass tile makers recommend it. It needs fast, careful cleanup, especially on matte or textured glass.
Why does my glass tile look darker after grouting?
Translucent glass picks up color from the grout at its edges and the mortar behind it. A darker grout or gray mortar will deepen the apparent tile color.
Why is grout cracking around my glass backsplash?
Usually because rigid grout was used at the countertop joint or inside corners, where glass and the substrate move. Replace grout there with a flexible sealant.
How long should grout cure on glass tile before a shower?
Follow the TDS, which is often around 72 hours for cement grouts and 24 hours to 7 days for epoxy depending on exposure. Glass slows cement grout drying, so allow extra time in cool rooms.
Sources and standards
- ANSI A137.2, American National Standard specifications for glass tile.
- ANSI A108.10, installation of grout in tilework, and ANSI A108.02 general requirements.
- ANSI A118.3, A118.6 and A118.7, epoxy and cement grout specifications.
- TCNA Handbook for Ceramic, Glass, and Stone Tile Installation, glass tile guidance and EJ171 movement joints.
- Glass tile and grout manufacturer installation instructions and technical data sheets.
Grout Atlas guidance is checked against ANSI A108/A118 and ISO 13007 requirements, the TCNA Handbook and manufacturer technical data sheets. Product formulations change, so confirm details on the current data sheet for the product you buy. Spotted an error? Report a correction.