What do you know about priming? Priming for microcement


Priming the substrate for microcement may not seem like a big deal, but it is worth paying attention to several important aspects of this stage of microcement application work.


What is a substrate priming for?

By covering the surface with primer, we increase the adhesion of subsequent layers to the substrate, reduce and even out its absorbency and prevent excessive soaking of microcement polymers into the substrate. If we apply the microcement without priming, it may come loose or bind poorly.


Do I always have to prime the substrate for microcement?

It’s always better to prime the substrate than not. In general, one layer is sufficient, while for a highly absorbent substrate it may be necessary to lay two or more layers. How to check it? On a properly primed surface you can see a delicate shiny foil, if it is not there and the primer has soaked into the surface, another layer is needed.

Surfaces that do not require priming are, for example, wet zones that have previously been treated with a liquid foil or other hydrophobic coating, or epoxy resin. All others, e.g. plasters, coats, self-leveling screeds, old floors, walls painted with paint, must be primed.


I will use a bonding bridge, do I have to use primer?

Yes, because the two products have different uses. The task of the bonding bridge is to increase the adhesion of the microcement to the substrate. It is used on slippery surfaces such as tiles. In turn, the ground balances the absorbency of the substrate. If we apply a bonding bridge to an absorbent substrate without priming, the substrate will “drink” the polymer from the bridge and it may come loose.

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Can I use a different primer than FestGrunt?

Yes, but it is safest and most convenient to use a primer from a microcement kit. Most of the good qualitz primers available on the market are compatible with our microcement. We advise against only the use of deep+penetrating primers.


How to prime step by step?

  • The surface should be solid, dry and clean. Any paint and other loose materials should be removed.
  • Shake the container with FESTGrunt well.
  • Apply the primer with a roller or brush.
  • Leave to dry for 2 to 4 hours.