Timber preservation

I have hardwood framed Everworst aluminium doors and windows. The wood appears to be coated with a coloured water based stuff, rather than varnish, which is flaking in places and has rubbed off the door sills.
Allowing for my biased description, does it sound as though I have identified the stuff correctly? Must I re-treat with similar water nased stuff? Can I use a non-water based solvent treatment? If I don't use similar stuff must I remove it before re-treating with something different? My prejudice against the water based treatments is based on my opinion that they seem to sit on the wood rather than soak into it.
What would you use and why?
Sorry if this post is duplicated - it seemed to dissapear!
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