Stains in Microcement Installed over Plywood
This guide tells you everything that you need to know about why you might see yellow stains when applying microcement over plywood and how to resolve it.
What Causes Stains in Microcement Installed over Plywood?
During the manufacturing process, Plywood is heated to high temperatures, this crystalizes the sap in the wood so that it is completely dry and free from movement. Occasionally problems occur in the process or materials that leaves some residual sap in the material.
The sap has a yellowish colour and is prone to leaching through materials that are applied to the surface, like microcement.
How Can I Block the Sap for Leaching through the Microcement?
If you are installing microcement over faulty plywood, then you will probably notice the yellow stains quite early on in the application. Usually after the 1st or 2nd base coat.
At this stage, the only way to stop it coming through to the surface is to use a vapour barrier like Impripox, followed by another coat of primer 100.
ImpriPox is a 2-part epoxy primer that will block stains from transferring through to subsequent coats. Primer 100 will ensure good adhesion.