Reasons that cause stains on microcement and solutions to marks. Processes to avoid possible imperfections.
Marking of tile joints
Some points should be considered to avoid marking tile joints:
- We should pay attention to the difference in absorption between tiles and joints: the
resin contained in the microcement is absorbed differently if no precautions are taken
we run the risk of them appearing in the form of a visual spectrum on drying (visual
pattern). Moisture in the joints also causes this defect.
- The joints are generally hollow, they are not on the same plane as the tile, the retraction of the Microcement once dry creates a relief in the joint area (relief pattern)
This is why with our system we create an insulating and levelling layer. For this reason it is very important that, after filling the joints, it is left to dry for 24 hours before starting the application of the microbase
Trowel marks, highlighting irregularities from the previous coat
We will have to apply the microcement without leaving burrs or reliefs that show the passage of the trowel, sanding these imperfections in each coat. If we apply over a layer with burrs, these reliefs will be copied.
With the steel trowel and excessive pressure, these imperfections cause the effect of "burnt" dark spots that reflect the lack of sanding of the layer below.
Sanding the irregularities
We will have to sand the microcement after each coat to avoid the effect described in the previous section.
We will carry out a soft grinding with a rotary-orbital sander of low revolutions or by means of a sanding glove, and silicon carbide sandpaper.
Approximately 3 hours after application, a change in the tone of the microcement can be seen, becoming lighter, this indicates that the microcement is passable and hard enough to proceed to sanding, the temperature, humidity and ventilation of the room influence this period of time.
We recommend sanding before 12 hours after application so that the coating has not reached an excessive hardness and this step is more complicated.