Good morning Grumblers,
Many of our resellers recommend Super Plak for environments such as bathrooms, garages, kitchens, restaurants, shops, with great success. Easy to clean, simple look, etc. As long as the product is not exposed to standing water where the paper can wick in moisture it should be fine.
As far as humidity goes, the MDF substrate is basically wood dust and glue. Like anything wood based, even frames, if the environment is too humid or there is exposure to excessive heat and/or sunlight the product can bow. Generally this is not a problem but be aware. As well general plak mounting is not suitable for outdoor areas where it will be exposed to the elements.
Often for more extreme environments such as bathrooms our recommendation is to mount the item to a sturdy substrate such as hardboard and laminate with a UV protective finish suitable to the image (matte, satin, linen, canvas, gloss). This negates the need for acrylic and/or glass and pretty well eliminates possible moisture build-up between the glass and the image. The finished mount can then be dropped into a suitable frame.
Though this is not for everyone, this is certainly an option that has many applications.
One last point, though I am not familiar with the corporate structure of ColorPlak, Super Plak is not a franchise and does not offer franchise opportunities at this time.
I hope my comments are helpful and I look forward to your questions.
Murray Scott
Super Plak