There were so many fun parts to this project, from collecting the acorn caps (and some leaves in the process)
We used two small packages of wool roving (one cream and one dark brown) and it made about 20 acorn bottoms. I found that the girls could roll it most of the way into balls, but needed a little help at the end to finish them off. As Syd's 5th birthday is coming up, I think we'll bring our finished product to school that day to share with her friends.
In case your curious little scientist asks, I wanted to add a brief explanation of why the wool roving felts into balls. Wool is a natural fiber whose shaft has an interesting characteristic in that it has what amount to little hooks coming off of it. Given the right circumstances, in our case: water, soap and friction, the hooks are able to grab onto each other and create almost a matted fabric. (Hence the problem with throwing a 100% wool sweater in the washing machine... massive shrinkage!) The wool from different breeds of sheep may felt differently from others. Also, many white or even cream wools do not felt well. This is because in order to create the white color, many of these wools are bleached which destroys that hook-like characteristic of the shaft so it is no longer able to grab onto other wool. We definitely found that to be true in the acorns that we made - the white ones were much harder to form into felted balls than the brown roving!