How to remove white stains and oil-like marks on newly installed bluestone?
Estimated Reading Time: 3 MinutesQ. I have laid 10 mm bluestone tiles in a bathroom. I sealed the backs before laying them and used a water-based adhesive. The floor beneath was fully waterproofed. White stains and what appear to be oil-like marks are now showing across the floor. These may be coming from the adhesive or from within the tiles themselves. Does anyone have suggestions for drawing out these marks, or is there a product that could be used to stain the entire floor to achieve a more uniform color? I would be extremely grateful for any ideas or solutions. Thank you.
A. While it’s disappointing to see problems like this on newly installed bluestone tiles, it doesn’t necessarily mean the floor is ruined. The type of problem you’re describing would usually be related to moisture and minerals rather than an installation failure.
White marks can come from two main sources: efflorescence or white hazing. Efflorescence is caused by moisture moving through stone and carrying natural salts to the surface. Efflorescence can also move through a substrate, but since your substrate is fully waterproofed, that's not likely happening. When the moisture evaporates, it leaves behind a chalky white residue. White hazing is usually a surface film left behind by adhesive residue, grout residue, sealer, or cleaning products that weren’t fully removed.
Darker or oil-like marks often come from moisture or natural minerals inside the bluestone. When the stone absorbs water from the adhesive, grout, or general bathroom humidity, these minerals and moisture can move toward the surface. Because the tile backs are sealed and the floor is waterproofed, the moisture can’t evaporate evenly and gets partially trapped within the stone. This trapped moisture changes the way light interacts with the stone, making certain areas look darker or oily, even though the surface itself may feel dry. Over time, these marks can persist or reappear as moisture continues to migrate through the stone.
For DIY options to resolve these issues, the first step is patience. Bluestone can take weeks or even months to fully dry out, especially in a bathroom with waterproofing and sealed tile backs.
A pH-neutral stone cleaner can help remove light surface haze but won’t fix deeper issues.
Efflorescence can be removed with a dry brush. If this cleans the surface, consider carefully whether sealing is necessary, as sealing stone in wet conditions may cause problems. In many cases, sealing should be delayed for weeks or even months, if it is done at all. If residue remains, clean with minimal fresh water and a soft brush, then dry thoroughly. For larger areas, lightly rinse and remove excess water. Avoid alkaline cleaners, which can worsen efflorescence.
You asked about staining the entire floor to even things out. This would be risky. Staining may not hide patchy moisture or mineral residue, and it can actually make uneven areas more noticeable. If the marks are widespread, persistent, or not improving over time, bringing in a stone restoration professional is usually the safest option. To find a vetted PRO in your area, visit www.surfacecarepros.com and click on Find a PRO. They can correctly identify whether the problem is efflorescence, surface haze, trapped moisture, or internal stone minerals, and they have access to stronger poultices, extraction methods, and honing equipment.
Just as importantly, a PRO will know when the stone is dry enough to reseal or enhance it so the problem doesn’t return. In many cases, professional restoration is far more cost-effective than replacement and avoids the risk of trial-and-error products making things worse.
ABOUT THE AUTHOR Fred Hueston is the Chief Technical Director at SurfaceCarePROS.com and Director at StoneForensics.com. He is also the author of Stone and Tile Restoration: The Manual, a comprehensive online manual for stone and tile restoration contractors. [Learn more about Fred.]