Sealing of natural stone

Sealing natural stone

Whether you are sealing marble worktops, granite countertops or natural stone splashbacks, it is important you choose a non-staining sealant when applying on natural stone surfaces. Most silicones contains silicone oil, which can penetrate into porous stone and result in staining. Once stained, it cannot be removed or reversed. 

Hybrid polymers, such as Fix ALL Flexi, have been specially formulated for use on natural stone surfaces. This means you can seal joints around marble, granite and other natural stones without any problems.

Guide to sealing natural stone


How to seal natural stone?

When applying sealants on natural stone surfaces it is important to select the right product for the job. Fix ALL Flexi is independently tested (conforms to ISO 16938-1) to ensure no staining when applied on natural stone and marble surfaces. Combined with its highly flexible and durable sealing properties, it is the ultimate natural stone sealant.


1. Prepare the surfaces

First, clean the surfaces to remove all dust, dirt and grease. Allow drying thoroughly before proceeding.

2. Tape off the joint edges

To achieve a straight sealant edge, use masking tape to neatly tape off the area. Make sure that the sealant joint is between 5 and 10mm wide.

3. Open the cartridge

Cut the tip off the cartridge with a safety cutter. Screw the nozzle on top and cut the end to suit the size of the joint you would like to fill/seal. Put the cartridge in the caulking gun and squeeze the handle until sealant appears.

TIP: For best results cut the nozzle at an angle.

4. Start sealing

Place the nozzle where you want to start sealing. Squeeze the handle and move the caulking gun over the joint in a smooth movement. Apply sufficient sealant to ensure that the product adheres well.

5. Smooth and remove the tape

Wet your finger in a soap solution or Soudal Joint Finish. Smooth the joint and immediately remove the masking tape. Once removed, carefully smooth away any protruding edges.

6. Rinse with clean water

Use a plant sprayer with clean water to remove soap residues. This prevents soap stains on the natural stone.



  • Most sealants do not adhere to damp surfaces. Do not seal outdoors if it has just rained or there is a rain forecast.
  • Make sure that you do not make the surface wet with the soap solution or finisher, or the sealant will not adhere well. So only wet your finger or putty spreader.
  • Is the sun shining strongly or is it very hot? Remove the soap solution or the finisher quickly so it cannot burn in and cause permanent stains.

The following is also useful:

  • Is the surface you want to seal very porous? Treat it with Soudal Primer 150.
  • Clean your tools immediately after use with a white spirit, turpentine or Soudal Surface Cleaner.

Click here to find the technical sheet and all information about the use, shelf life, composition of Fix ALL Flexi.

Fix ALL Flexi Grey 290ml
Hybrid polymer sealant adhesive

How to seal natural stone

Product suggestion: Fix ALL Flexi


Safety cutter

Masking tape

Clean cloth


Soudal Joint Finish or soap solution

Plant sprayer with clean water