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Crackle Glaze Tiles & water marks

Published 3 Dec 2015


We were recently contacted by a customer who had concerns about her crackle glaze tiles that were installed in a shower area & sealed with LTP Crackle Glaze Sealer.

After using the shower small dark spots appeared. See images below.


When newly laid crackle glaze tiles are fitted they will expand and contract with the change in temperature, especially in a wet room. This causes new cracks to form in the glaze, this new crack will be slightly porous and this will continue probably for about 6 months until the tiles have fully settled.

The customers concerns are as follows our answers in blue.

Q. Can mould grow as water can penetrate the tiles?

A. As far as we can gather from the information provided the dark marks that appear are drying out between wetting so the retention of moisture is relatively low. If ventilation in the bathroom is adequate, then we would not expect mould growth to be an issue. Cleaning the tiles with LTP Stonewash on a regular basis will help keep the surface clean without compromising the protection.

Q.Is the Crackle Glaze Protector adequate on its own? Why do you recommend the use of LTP Tile & Grout Protector Aerosol?

A. Crackle Glaze Protector contains a nano polymer that helps bridge the gaps between the crackles in the glaze. Filling these micro voids helps to ensure that stains and residual grout do not fill the cracks in the glaze, potentially altering the original character of the tile. Despite being an effective stain blocker the sealer does also need to remain breathable. This ensures that microscopic transition of moisture can still take place, even after the sealer has fully cured.  If moisture gets behind the tile then it should till dry out.  If moisture passes through a newly exposed crackle in the glaze due to settling then it should also still dry out.

Some customers prefer the convenience of topping the protection using the grout & tile protector because it is quicker and easier.  The polymer used in the grout & tile protector is slightly larger, so we would not normally suggest it is used as a primary sealer in place of the Crackle Glaze Protector on crackle glazed tiles

Q. Are tiles that have a water absorption rate of greater than 10% considered suitable for bathrooms?

A. Provided that the crackle glazed tiles are set into a flat even bed of adhesive with full contact to the reverse side of the tile without any voids, followed by a sufficient seal, then there should not be any great issues with water absorbsion/retention. We have seen on a  number of occasions installations where tiles have not been set into sufficient bed of adhesive allowing for voids between the all and the reverse side of the tile.  In wet areas such as shower enclosures moisture and condensation can build up behind the tiles and dwell within the open voids.  If the tile used has a relatively absorbent biscuit, then this moisture can travel from the reverse side of tile through to the face leaving a water mark that can take a longer time to dry out.

crackle-glaze-pic-4Crackle glaze tiles that have been sealed.


It is also recommended to seal before grouting or cutting the tiles, as grout can also enter these small cracks and become almost impossible to remove. There are different methods for sealing dependent on what colour grout is being used.




For regular cleaning the of the tiles we recommend using LTP stonewash, this will help keep surfaces clean without compromising the protection.




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Please note that this information is offered as general guidance only and without guarantee. Your specific circumstances may need an alternative approach. In case of doubt, any process should be tried out in an inconspicuous area before general application.