Mounting on root stock

[louis hurn]

Hi, Most of my orchids are mounted, on driftwood root stock and Australian bottlebrush. I have a lot of stunning old pieces of root stock, but some of them were varnished (about 15 yeasr ago) I would like to mount some Catts on them, but I do not know if the old varnish is ok? In the meantine I have tossed them into the swimming pool (about a week ago). Maybe I should try one? or has somebody already tried this?
Greetings, Louis.

[thakshila smith]

some people grow them on cement based surfaces.
So try one plant and see.