It struck me that although I responded to a question by a reader a while back about paint stripping, I've never put it on the blog. So as I stripped those sashes, I did the play-by-play photos. (Yes, I got a new camera charger). Following is the procedure we use, pasted from my response to the comment, and with window-specific details added. Note that I ALWAYS use citristrip on sashes - it works well, doesn't damage the glass, and it's my old standby. Other methods are better for other house parts (heat gun for trim, peel away when I'm tired of stripping, etc.) Also note that you should ALWAYS test what you're doing on a piece that will be hidden or that is not your favorite window - all the old materials and types of paint have their own personality & you need to first make sure that what you're using won't cause damage.
We use a variety of paint stripping methods, depending on the job and sometimes the mood! We assume everything is lead paint, so we never ever sand anything. We use a heat gun for starters, to get the big stuff off. This works really well in our house, because they painted right over the old shellac/varnish, and the heat gun basically heats up that shellac layer, and it slides right off with the paint. You can see the varnish on the back of a heat-gunned piece of paint, below.
Then I go back and clean up using a wet stripper - sometimes I use citristrip, sometimes peel away. If almost all of the paint is gone, I sometimes just scrub with a green scrubby pad (like scotch brite) and regular old rubbing alcohol - but you should test on a small section first because the alcohol can darken some woods, and if you have light wood, the green scrubby can stain it green! I would test everything, frankly. I always wear gloves and usually a respirator for fumes. You'll need lots of gloves - they get gross and splinters will puncture them, then you'll start leaking! Splinters are a serious issue - even with gloves I usually have lots that often don't come out for a while - I've had some real painful ones. I sometimes wear those rubber-dipped work gloves under my rubber stripping gloves if I'm getting a lot of stabs!
On windows, I always use citristrip. It's gloppy and gross, but it's my old standby and it works for our unique combo of old disgusting paints. I do them outside. We never take the chance of cracking window sashes with the heat gun, which is why I always strip those wet.
Step 1: apply the stripper. Let it sit. Often overnight. Just let it work, I'm telling you. Then gently scrape off the paint. Words to live by: just scrape off what slides off. Don't try to physically scrape. The wood gets soft with the stripper on and you will gouge it.
Step 2. Apply the stripper, again, if necessary. Often there is a particular layer of paint that is either on there really well or is a different type of paint than other layers, and it can act as a barrier. Get off what comes off the first time, then re-apply. After many times doing this, it is quicker and way easier than working really hard to get those last bits off with a scraper (and you damage the wood less). Then gently scrape that off. Either apply again or go to the next step.
Step 3: clean it up. However we get the majority of paint off, after that I clean up the little stubborn bits by scrubbing with wet stripper & green scrubby. Take your time here, scrape the little bits out of the corner now, because even though it's oh-so-tempting to say "I'll just sand them later", it's impossible to do that. Just get it all off while it's still goopy.
Step 4: really clean up. You can use alcohol & scrubby, or whatever the stripper manufacturer suggests. Your call. Get it clean, you'll probably have a bit of hazy residue but you want to get the stripper to stop working so things can dry out.
Step 5: Let it rest. I don't touch them again for a few days. The wood needs to dry our; it gets soft during the process. Plus you'll be sick of dealing with the windows. When you come back to them, they'll look pretty good. Then we do the world's quickest sanding with like 150-ish paper just to remove any stripper residue and smooth out if there were any splinters or raised grain (or wood filler for the millions of curtain rods they HAD to install), then tackcloth and finish. Woo hoo!
Oh, and in our case, now turn them over, fix all the exterior problems, reglaze, then re-finish all the rest of the window parts, THEN install. We're getting there, though.
Other tidbits of info: Peel away claims its ok for inside, so I use that on trim that isn't removed (if the heat gun wasn't appropriate for some reason, like carvings or places the heat gun won't go). You'll need a bunch of dental picks, scrapers, etc. to clean up some spots. A really dull chisel works well for a lot of things - it doesn't tend to accidentally gouge the wood. Wear clothes that you wouldn't mind throwing out. Sometimes it just gets too messy & gross, and if your paint is potentially lead, you'll want to kiss them goodbye. And - ventilation! This is all stinky and not the healthiest thing to do, so get yourself plenty of fresh air or do it outside.
Windows take PATIENCE. Repeat: PATIENCE. In fact it all does. When you first start you'll wonder how you'll ever finish, but you just have to keep plugging and take lots of breaks/come back to it later. I find that I actually kind of look forward to it now! The results are so satisfying, it is always worth it - we have beautiful flat-grain fir under there! If you can master pulling the trim out and working on it outside in a workshop/garage, it's much cleaner and easier that way. Disclaimer: I'm an amateur and I'm just telling you what we do, no implied warranties, etc. :)
There's nothing like a beautiful old wood window. They look and work great, you just have to get them cleaned up and tune them, and they're miles better than vinyl. But don't even get me started on that issue...
Sorry about the odd spacing on this post - I don't know what's up with it! Out of time to worry about it...