Lime plaster needs a primer if the substrate is absorbent

Lime plaster develops its durability and stability from a time-optimized setting phase. The escape of the water must take place at a controlled speed. In addition to external conditions such as temperature and drafts, the suction behavior of the subsurface may have to be adjusted with a professional primer.

Primers serve several purposes

Primers form the holding and contact layer between the masonry and the lime plaster. They have different influences on the applied interior plaster or exterior plaster:

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  • They accelerate the loss of water from the plaster
  • They slow down the evaporation of the water
  • They bring the lime plaster and the substrate to a clawed hold
  • They compensate for differences in tension caused by the plaster's shrinkage

Some walls and materials have almost the perfect properties to function as a substrate for lime plaster. This includes some types of concrete that can be plastered directly without a special primer. Before laying the plaster, it is sufficient to moisten it, if necessary with lime water.

Check absorbency and choose a suitable primer

To test the absorbency of the surface, simply sprinkle it with water. A painter's brush dipped in water is used once as a "water thrower ". The wet surfaces indicate the absorbency. If the water runs down the wall in drops before it is absorbed and evaporated, there is little suction. The medium to strong suction intensity is shown by the speed of drawing in without water running off.

If the absorbency is very low, an "adhesive aid" may be necessary as a primer. The suction power must be reduced on medium to strongly absorbent substrates. There are two types of primer for this:

1. The depth reason (4,81 € at Amazon *) acts like a "clogging " of the capillaries and pores in the substrate and reduces their suction effect.

2. The primer (36,80 € at Amazon *) serves as a kind of "glue ", which produces and supports the mechanical and physical connection of the lime plaster with the subsoil.

An additional criterion for the selection of primer is the nature and type of lime plaster. The amounts of water contained in the cleaning mix differ depending on the type of processing. A primer must additionally be set on factors such as harshgrasting, friction plaster and string.

Tips & Tricks A kind of "natural " Priment support can be achieved by roughening the surfaces of the substrate. In a similar way also help with a toothed trowel distributed primer spatula.