Furniture, Wood and Cabinetry Finishing - Refinishing window sills?

I'm refinishing some window sills to repair water damage. The sills are pine covered with a varnish-stain. I have some matching stain and varnish which comes pretty close. One of the sills has areas where the old finish is completely gone. If I stain that directly, the bare pine will take the stain much darker than the surrounding areas. Is there anything I can do so that it won't take the stain so heavily, so that it blends in with the surrounding finish? Thanks.... :)

I've refinished a lot of window stools, and you rarely get good results unless you actually remove the stool from the sloped sill. Usually this is just a matter of removing the interior window stops (the side pieces butt into the stool on the bottom, and must be removed so the stool will be able to slide out.) And then there are usually nails down through the stool which must (carefully!) be cut with a reciprocating saw. Sometimes it helps to gently pry up between the stool and the sill to create a tiny gap for the reciprocating blade. You need to open the window and hold the reciprocating saw out the window to get at these nails. It's not easy until you've done 1000 of them or so. ;)

You can certainly try to sand the stool down in place, but it's difficult to do a nice job of sanding around all the edges. If that's the route you decide to go, you will have to sand off all the varnish, and sand off enough of the stain so as to lighten the wood up a little so that your new stain will go on evenly. You can't refinish just part of the stool and expect it to blend in, you're better off stripping the whole thing and refinishing it.

The good news is that usually, the old varnish is pretty easy to sand down with 100 or 120 grit sandpaper. It's usually baked by the sun pretty well. The areas that aren't in direct sunlight are always a little tougher to do, but paying a little extra attention to these areas will make the job look a lot better.

I'm really sorry, I'm such a noob....what's a window stool? :confused:

Maybe I used the wrong term when I said "sill"? :(

The window stool is what you are reffering to as sill. It is the piece of pine that sits in front of the window with a small piece of trim under it and the bottom of each side casing resting on it.

Window stools are hard to restain. The weathering they take often makes them obsorb more stain. Sometimes you can first paint them with a wash coat of varnish [thinned 50%] which will slightly seal the wood allowwing less stain to penatrate. Removing and sanding it all down to good wood will give the best results.

I think the sanding and sealing is what I want to try. Just use mineral spirits to cut the varnish? It's Minwax polyurethane. (I can't read the label on the can....it's only a half-pint can) Thanks....