On Monday, 4 February 2019 12:54:33 UTC, Tricky Dicky wrote:
Seal the MDF first, PVA will do.

Richard

With respect, PVA should never be used as a sealant before tiling. If it gets wet it will fail. Use something like Mapei Primer G which isn't expensive.

https://www.toolstation.com/mapei-plaster-primer/p57804