I have painted two slatted wood chairs white, (slats run horizontally). The slats are 1.5" wide and the gaps between are 1/2". I tried painting black stripes to imitate piano keys along the side edges. However with the gaps in between it has ended up looking more like a upc code. I need to fill in the gaps where the black keys would be. I have thought of using paint stir sticks, painting them black, to connect the gaps where the black keys would be. My husband thinks it will be hard to glue them on the painted surface of the chairs. Is there another way to fill in the gaps on the chairs, or can you suggest a better way to adhere the "black keys", which will be painted, to the painted chair. These chairs are to be donated to a church auction, and I don't want them to fall apart quickly. Thank you for any suggestions. Penny
Generally speaking you are on the right train of thought - gluing in a filler panel. I would stay away from paint sticks, they are very thin and will not hold up to the forces working against a chair. You probably want to use material that is at least 1/4" thick.
As for securing them, wood glue (PVA) will stick best to freshly sanded and clean wood; scuffing up the paint will provide for better adhesion but still not as good as wood on wood. Epoxy is an option as mentioned in another answer but is more difficult to work with and if not mixed properly or in the right proportions, will not work as-expected.
I think your best case scenario is sanding down the painted areas to accept glue, gluing in the new panel, and then re-painting the piece.
e-p-o-x-y. just mix and fill. once dry, sand and paint like wood.