Black polished clay plaster washroom by Becky Gilling

A video from Becky Gilling's instagram account @rebecca_gilling:
"Recently completed black polished clay plaster washroom for @foxglovehouse_. Completed in just 3.5 (long) days!
I'd love to do more projects like this, I've got a couple of weeks spare in December and then I'll be taking bookings for next year. DM me if you have an idea you'd like to discuss.
Plaster mixed by @william.stanwix"
Follow Becky on Instagram: www.instagram....

[@dcoakley3590]

How do you make the Clay waterproof? Oil added to mix?

[@ge2719]

other videos ive seen used linseed oil as a final coat