You can add muntin strips or dividers to dolls house windows in a range of decorative patterns. It is best to apply the muntin strips only to the outside of the window as it makes cleaning the tiny windows much easier, but you can apply the strips to both sides if you wish. I have shown the muntin strips unfinished in this project, but you should paint them the color you want them to be before glueing them in place to save yourself a lot of cleaning an detailed trim work!
If you are going to add muntin strips to a window, choose a piece of wood trim which is roughly 1/2 inch to 3/4 inch in scale. Fine wood strips suitable for dolls house muntins are available from model ship lumberyards You can also used decorative sticker strips available from scrapbook suppliers, similar to the strips used for making stained glass. If you must, you can paint these sticker strips while they are attached to their backing sheet. I used wood muntin strips on these windows which are roughly 1/32 inch square. The thickness of your muntin strip should not stick up above the edge of your window sash material. If you need to use thicker muntin strips, custom make your windows from stripwood so your sash material can be thicker than is available in the U channel.
Once you have your muntin strip trimmed, glue it in place on your window. I usually only glue the edges where they meet each other or the sash, I don't glue the strips to the glazing. As thin stripwood is easy to bend when it is damp, you can also create curved muntin strips fairly easily. Allow the damp wood to dry before trimming it to size.
