Wooden window was painted shut. How can I get it open again?

Hi Mararite, it sounds as though you have the right idea for "breaking" the seal that has been made with paint. Perhaps using an even narrower blade such as a razor blade might help to slice the paint barrier. Then you may have to use brute force to slide the window open the first time. Here is a link with specific info and a tool called a window zipper made by Red Devil that you may need to try to finally remedy your problem, especially if you have several windows to get unstuck. I hope this is helpful to you.

https://www.thespruce.com/loosen-painted-over-window-1822922

I agree that a razor blade, or perhaps a thin, sharp knife would work to break the seal.

Is the problem compounded because of humidity (wood swelling)? Can you run air conditioning or dehumidifier to dry up humidity? If the previous owner used oil based paint, you may need paint stripper to get through some of the layers. I wish you luck!

You definitely do need to use a razor knife. It could also be because of the humidity. You can also look into stripping some of the paint away with something like the citrus paint removers.

Use an X-acto knife or carpet knife, with a longer blade. You may have some paint that dropped into the metal guide. Add a little baby oil, Vasolene petroleum.jelly, or olive oil on a bit of cotton stuck on the end of a plastic straw. The straw will automatically flatten as it is forced to by the guide. If the cotton comes off, it will eventually come out with use of the window. Lift the window a little bit to help break the seal of the paint. Good luck, Margarite! ☺️

I agree with using a razor box knife. A few passes to cut through the paint.

Ok thank you.