I'd like to treat some wood (raw pine) with a water-based class A flame retardant (Flameseal WSA), but also stain it with an oil based stain (garden variety Minwax or Varathane).
I'm a bit unsure of compatibility, and the need for a barrier layer (e.g. shellac) if any.
The FR datasheet states:
This product may be used on most types of wood as long as penetration occurs. The product may be stained with a compatible stain or top coat after treatment. However, many stains and top coats are flammable and can adversely affect the flammability of the treated substrate.
The priority is FR effectiveness over looks, but I'm concerned because the flame treatment is penetrating, then if I have to put a coat of shellac over top, I'm thinking any stain on top of that isn't going to penetrate well. I'm also concerned that, even worse, the stain will never really dry properly. The wood will be used on a ceiling so at least any finish doesn't have to stand up to heavy wear and tear, although if it stays sticky forever it will attract dirt.
So my main question is: How can I apply both the water based FR and the oil based stain and get the most out of both?
My second question is, given the last sentence of that quote above, should I be considering a water-based stain or some special FR stain instead of my go-to oil stains? Does anybody have any experience with this?
I only actually need a class B rating (these are ASTM E84 ratings) so I do have a fair bit of leeway with reduced FR effectiveness, if it matters.