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Tue, Aug 16, 2022

How To Seal Mosaic Grout


Learn how to seal grout to protect your mosaic from the three m's; mould, mildew and moisture (oh and stains too!) Sealing your grout is easy! This guide answers why, when and how to seal your grout.


What is Grout?

Grout is a porous material made of a cement compound that is mixed with water into a paste, which is applied by spreading it over the tiles/tesserae.

how to seal mosaic grout; why, when and how to seal your grout

Why Do You Seal Grout?

Sealing grout is necessary for pieces that are going in kitchens and bathrooms and for mosaic pieces that are going outdoors. These pieces can come into contact with mould, mildew, moisture and soil (outdoor mosaics). It is also a good idea when using a light-coloured grout in a project that is susceptible to staining. Sealing grout on pieces in these environments will help prolong the look and life of your mosaic.

mold on mosaics

When To Seal Grout?

You should seal your piece before it is exposed to the elements. Why? If you wait to seal your mosaic later, you could be trapping mould, mildew, moisture and dirt in the grout.

Allow the grout to cure for three days before you apply the sealant. Check your piece for any cracks in the grout before sealing, repair and wait three days before applying the sealant.

Don't seal porous surfaces like stone or unglazed tiles; it will be absorbed, and you won't be able to wipe the sealant off.

Don't seal porous surfaces like stone

Types of Grout Sealers?

There are two types of grout sealers:

1. Penetrating Sealers

Penetrating sealers have a water base that allows particles to penetrate the grout. As grout is porous, it absorbs the sealer, keeping the moisture out — the most common type of sealer and the best choice for damp areas.

2. Membrane Forming Sealers

This sealer forms a membrane on the grout, preventing the moisture from getting it. These sealers can trap moisture in the grout and cause mould and mildew in outdoor environments.

We sell a penetrating grout sealer manufactured by DTA.

shop mosaic grout sealer


DTA  grout sealer

How To Use a Grout Sealer

Warning: Sealing grout take time and patience

1) Read the manufacturers instructions before starting

2) Use an old paint or sponge brush to apply the sealer.

3) Two methods of applying the sealer

a. Painting the sealer methodically onto the grout lines. This can be difficult when working with small tiles and fine grout lines. This method takes time.

b. Paint the sealer over the surface and go back and wipe the sealer off your tiles. Try to keep the sealer off the tiles, but don't worry if you can't. Ensure you wipe the sealer off your tiles before it dries; otherwise, you may be left with a foggy film on the tiles, which is difficult to remove.

4) Once you've applied your first coat, wait 15 minutes and apply a second coat. Check the manufacturer's instructions to see how many coats you need to apply.

5) Leave your mosaic for a few days before your mosaic goes outside permanently.

mosaic grout sealer


Legal Disclaimer: No warranty is implied by these instructions. Use at your own risk. The Mosaic Store and its proprietors are not responsible for the results of any actions taken based on this information, nor for any omission in the advice. Please wear appropriate safety equipment when cutting mosaic materials and using grouts and adhesives. Keep out of reach of children.



Aqua Porcelain Rondel - 6cm


Dark Blue Porcelain Rondel - 6cm


Green Porcelain Swirl - 4cm


Red Porcelain Swirl - 4cm