The students love it because they get to see the colors migrate up the paper and it's applicable to their everyday life. Some teachers who have done this lab before recommend using coffee filters, but I find that because they are usually so thin it can be hard to see the color separation. That's why I use filter paper. I cut the edges of the circles to leave a rectangle, and it works like a charm. Here are some pictures of my students completing the lab - I'm always amazed how well the NaCl solution separates out the dyes!
The students really did a nice job. And clean up is a snap - no messy chemicals or glassware to clean. The post-lab questions make assessing your student understanding easy. This product is available on my TeachersPayTeachers site - and great for younger students all the way up to high school. It even includes a helpful teacher prep guide that tells you everything you need to carry out this lab with ease. Instruction for setup and making the solution are provided as well. Try it - your students will really enjoy this activity as mine have!
Thanks for reading!