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Sealer Issues

Issues with dull,worn or milky sealed surfaces


As discussed in the FAQ section of our website, solvent-based sealers are used to protect and enhance the look of plain and decorative finished concrete areas. Whether it's a water-based sealer or solvent-based sealer, the finish is a thin film of acrylic polymer which has bonded together to form a seal of the treated area. The process is described in our FAQ. 


Over time, acrylic sealers may become dull or cloudy. Normal weathering events, traffic or chemicals (from washing the car!) may cause the sealer to exhibit signs of wear, and some may believe that the sealer has gone! The problem isn't that the sealer has gone, it's that it has worn to the point where it is no longer transparent. The time that sealers take to become dull or cloudy looking is dependant on the circumstances under which the sealed area is used... High traffic areas in Industrial complexes may show the tell-tale signs of wear quickly, whilst low-traffic areas may last for many years without exhibiting any signs of wear.


Another issue is a cloudy sealed finish, where moisture has become trapped beneath the sealer and the sealer turns 'milky' in appearance (also known as blushing). Despite having sealed the concrete perfectly, during the driest conditions, you notice some milky or cloudy patches occuring in random spots. What could possibly have happened?


Although it was dry and the sealer was applied as directed and allowed to cure fully and looked perfect for a while; rainwater runoff, ground-water or control joints may have allowed water to flow underneath the concrete slab. Concrete, being a porous substance, has literally soaked up this underground water (this process is called wicking) and through evaporation, is attempting to expel it, through the sealer on top. The result is that the moisture causes the sealer to become cloudy or milky looking.


'Whitening' is a problem that may occur several days after concrete has been sealed. It is characterized by an excellent quality finish immediately following the application of a sealer, followed by the appearance of frosted or whitened areas several days later.

Concrete is a very porous material and there is always water vapor passing upward through concrete, drawn upwards by the warmth of the sun. As a result, whitening is generally most pronounced in areas of greatest sun exposure and less evident in shaded areas.

Acrylic sealers are designed to “breathe”,which allows water vapor to pass through but prevents liquid water from being absorbed back into the concrete. If a sealer is applied too heavily or frequently, that breathability is compromised allowing water vapor to condense beneath the sealer, causing it to delaminate from the concrete surface. The delaminated areas appear white.


'Blushing' is a milky appearance within the sealer itself. Blushing of water-based sealers is either moisture trapped within the sealer as it cures, or the film hasn't cured correctly. Film formation (especially of water-based products) is inhibited by low temperatures (air and/or substrate temperatures below 10°C) and high humidity that slows evaporation.

Fixing dull or worn sealed surfaces


Whilst the first reaction is to reseal the concrete, this isn't necessarily the best option...

Adding more sealer will, for a short while, return the finish to looking brand new, unfortunately the thick layer of sealer will be even more difficult for water to evaporate through the concrete, causing more problems in the future.

This tip is for use with our solvent-based sealers: 310, 311, 312, 313, 314, 321, 331

Our tip to fix dull, abraded or milky sealed surfaces is to apply a coating of 399 Solvent directly to the surface with a solvent-resistant paint roller. The solvent will soften the sealer and rolling it will evenly spread the polymer solids over the surface.


The solvent will then evaporate naturally and the sealer will be returned to clear and look like new. Remember, Xylene solvent evaporates quickly and it's important that enough solvent be applied for the sealer to soften up enough to be able to be re-distruibuted when rolled. The approximate coverage rate required is 1L:7.5m².


Note: with any solvent based product, care must be taken when handling or using them. Be sure to read all warnings and technical data sheets before use, keep clear of ignition sources as these are classed as flammable products and ensure you wear your PPE (Personal Protective Equipment).

This tip is for use with our water-based sealers: 401, 402, 403


The fix for water based sealers is similar to solvent-based sealers.


Apply a coating of 399 Solvent using a solvent resistant sprayer to the affected area. The approximate coverage rate required is 1L:7.5m².


Allow the solvent to remain on the affected area for 1-2 minutes until the acrylic soften. It may be necessary to use a natural bristle broom to gently scrub the acrylic, using care not to disrupt the highlight colors in stamped concrete, to ensure the acrylic becomes soft. Then, with a solvent resistant roller dampened with solvent, roll in one direction to evenly spread the acrylic back over the affected area.


Take care to not cause bubbles (by over-working) when rolling or leave roller marks, as these will be noticeable once the sealer has cured again. Allow the solvent to evaporate naturally and the sealer to dry. It may be necessary to repeat this process if the acrylic buildup is excessive, i.e. if multiple layers have been applied.


Note: with any solvent based product, care must be taken when handling or using them. Be sure to read all warnings and technical data sheets before use, keep clear of ignition sources as these are classed as flammable products and ensure you wear your PPE (Personal Protective Equipment).


Warning - When attempting to correct any of the above problems, it is always recommended to use a small trial area to confirm expectations are met.


Additional Tips: Work in smaller areas that you can reach with a long handled roller. The best conditions to attempt these repairs is on a cool, overcast day with no wind.

Please feel free to contact us if you have any other questions.