How to seal MDF for mosaics?

[Tala]

Hi, 

I would like some recommendations of products to seal MDF sheeting for mosaic work. Currently the undercoat I use is British paint white prep 4 in 1 water based primer sealer undercoat. It would be indoors but ideally I would like to seal and make it as moisture/water resistant as possible. Any recommendations of what to add underneath any white base coats to ensure minimal moisture? 

Thanks! 

[MitchellMc]

Welcome to the Bunnings Workshop community @Tala. It's brilliant to have you join us, and many thanks for your question on sealing MDF.

Could you tell us a little more about your need for the MDF to be moisture/water resistant? Typically, your mosaic won't see significant moisture or water if displayed indoors. Do you intend to hand the mosaic in a bathroom or high humidity environment?

If the mosaic is displayed in your home, coating the MDF's rear side with varnish will seal it adequately. Or, an enamel paint will also do an excellent job of preventing water penetration. You might even like to use Boyle Clear Matt Spray Sealer if it's more convenient.

The front is already sealed with your white base, glue, grout and tiles. It would be tough for moisture to penetrate the front of a mosaic unless it's kept outside in the weather. For an additional layer of protection, you could apply Davco Sanitized Tile and Grout Sealer. This will prevent any moisture from penetrating the surface of the mosaic.

Please let me know if you have further questions.

Mitchell
 

[Tala]

Hi Mitchell, 

Thankyou for your response. 

this advice is for various locations. Possibly could be exposed to humidity. If it is exposed to moisture but indoors how is it best sealed? 

Also with enamel paints, am I able to use water based paint on top of this? 

thankyou again for your assistance 

Tala

[MitchellMc]

@Tala,

The suggestions I've provided above would be suitable for most scenarios inside a home. If it's going right next to a shower stall, we might need to rethink. If that were the case, I'd recommend you use a board more suited to moisture exposure, like marine plywood. MDF is highly susceptible to degradation in moist environments.

There are plenty of acrylic water-based enamel paints these days, like the one I linked above. You'll be able to cover them with your acrylic paints.

Mitchell

[Tala]

Appreciate your assistance! 

Thank you again 😊