I would google this except I can't figure out what it would be called. I need more multisensory things for letter formation as one of my little students is strangely resistant to the carpet board. I was thinking of making something I've seen others do, which is putting hair conditioner or gel into a large ziploc bag such that when you make letters on it with your finger, it leaves a line behind. I suppose it would be easy enough to play around until I figure out what works, but if someone has a formula already, I'll follow. I wonder if there's anything I could put in that would give a nice swirly effect... not food coloring, that would just turn into brown smush quickly enough.