How to avoid unwanted stains or marks when applying Microcement

The following illustrates how the most frequent stains or marks are produced, and how best to work the material to avoid these imperfections

Lines at the joints between tiles

Some points should be considered to avoid the marks of the tile joints:

  • Attention must be given to the varying absorption qualities between the tiles and the joints: if no precautions are taken the resin contained in the Micro-cement will be absorbed differently and risks the appearance of a spectral image (visual pattern) when dry. Moisture in the joints also causes this defect.
  • The joints are generally hollowed, lying beneath the level of the tile, once dry retraction of the Micro-cement creates a relief or embossed pattern in the area of the joints.

Consequently, with this system a layer is created that insulates and levels the area.

marcas de las juntas de los azulejos por humedad

Trowel marks, highlighting irregularities in the previous coat

The Micro-cement must be applied without leaving burrs or reliefs that indicate the trowel’s movement, and any imperfections sanded after each coat. If a layer with burrs is applied, these reliefs will be reflected in this following coat.

With a steel trowel, plus any excess pressure, such imperfections cause the "burnt" effect, namely dark spots that reflect the lack of sanding of the coat beneath.


Sanding of irregularities

The Micro-cement requires sanding after each coat to avoid the effect described in the previous section. A gentle rubbing-back will be done with a low-speed rotary-orbital sander or sanding glove, and silicon carbide sandpaper.

Approximately 3 hours after the application, a change in the Micro-cement's tone becomes apparent. This indicates that Micro-cement is crossable and hard enough to sand, with the temperature, humidity and room ventilation causing a variation in this process.

Sanding is recommended not later than 12 hours after application, so that the coating has not hardened excessively which would complicate the finishing touch.

marca de quemado de llana



Stains caused by excessive sanding

When sanding the final Micro-cement coat, it is imperative to work smoothly, one hand taking the sander or wearing the sanding glove, while the other uses the sense of touch to check that the sanding is correct. If done carefully, the three types of characteristic stains: circles, contours and black marks will be avoided.

The sander will need to be of the rotary-orbital type to avoid leaving circles. It should be kept moving in a constant way without prolonged impact in the same place. If the sanding is excessive, the Micro-cement of the previous coat would become visible, leaving some characteristic "curves" that would indicate that they are from the lower layer. As soon as the sandpaper is worn it should be changed, as failure to do so will cause the old sandpaper to change from sanding to polishing, leaving black marks on the Micro-cement.

Excess burnishing of the Micro-cement

Any touches as the Micro-cement begins to dry will leave clear and unattractive marks, the most appropriate action should the finish not be that desired is to re-apply an additional coat.

Excessive over-working of an area with the trowel will leave dark marks. This can happen, for example, when material accumulates at the end of the application path on floors, necessitating the picking up of any excess Micro-cement, causing over-working with the trowel.

If an area is over-worked, the drying process is forced, which will cause a whitening of the area. For example: a black wall might have grey stains which are much lighter than the selected colour.

If the entire surface is over-worked, or the operator presses too much, then the entire surface will have a lighter colour. It is very typical with this problem to see a black wall that looks grey.

Avoid cutting marks on a floor covering

To avoid split marks in floors, produced by the drying of the material and subsequent cracking, keeping a cord of fresh Micro-cement is recommended in order that the work can be extended and replenished. This procedure can be seen in the following video.

Drying times before sealing

Care must be taken not to stain Micro-cement with any type of liquid, even water or sweat, before the application of the sealant. Such a stain would become visible after the sealing operation.

Roller Marks in the sealing

Roller marks are produced by applying unequal layers of sealant. When the roller begins to dry and is recharged, work should not be continued from the last position we found ourselves at, but rather it should be continued at palms’ width forward, and the sealant worked backwards to complete the surface. When starting from a corner it is essential to cover the total height of the wall, or the width in the case of a floor. Do not allow the roller to dry and recharge it frequently. In this video, you can see how to take due care and thus avoid the appearance of roller marks in Micro-cement.