In instances like these I usually just start out getting the supplies set up to work with as though I am going to make the shaving cream- paint myself and with in minutes I have the entire class gathered around begging to help; so... I let them ;-).
I let them empty the shaving cream container and whip it up, I had to pour the glue because the container is quite heavy. They decided that they wanted to have blue and purple paint so I split it into two containers added blue to one and asked them what colors to add in order to make purple. One child answered blue and red, another red and yellow. We talked about it and took a vote to see which way we should make purple- we ended up with orange paint, so you can tell who "won." I make a habit of using only primary colors fairly often so that they can discover how to make secondary colors on their own.
The end product is a little firmer, a little more slimy, and a little more sticky. It is in every respect as GREAT as shaving cream though.
Both of these bowls were completely full and I used only one can of shaving cream. The result was enough for 14 papers with as much shaving cream as each child wanted.
After they washed their hands they came to the other table where their papers were waiting for them with bottles of glitter and two baskets of odds and ends we use for collages. As many of you know, there is no such thing as too much glitter.
One of the most amazing things about this shaving cream is the amount of material it can hold on the paper. All of these things went up on the wall as they are and lost little, if any glitter or collage materials from them. It almost works better than glue it self. The other amazing thing about this is how it feels when it dries. I can't even quite describe it, so you will have to try it at home for yourself.
Something that I often do in my classroom with art type things is to do the same thing the next day with a slight variation. I do this for a few reasons. First, children learn, experience, and experiment in repetition. The other reason is that often even if they get to do the project two or three times the first day they would still have done more if they didn't have to leave or go to lunch. They almost always are really happy to do it again the next day.
The second day of this project we started out by making our own "sparkles," (their word for glitter, colored sand, or any similar substance), in preparation for the shaving cream art. I poured them each a small plate of kosher salt, (I don't think it is important for it to be kosher, it was just what we had), and they went straight to work coloring it with chalk. Each child made at least two plates, which were set aside for them to use later.
While most of the children sprinkled the salt on like glitter, two of them mixed the salt into the shaving cream mixture. When they mixed it in they were able to pick up the shaving cream off the paper in a ball of what looked and felt like crystallized dough. They then squeezed it and water came out of the ball, and the ball compressed. They had no artwork to show for it except the ball- which remained the same after "drying," but it was a really cool experience for them.
Below you can see some of the artwork from the second time we worked with the shaving cream- paint. This time they chose pink and purple and remembered how to make purple from the trial and error session the day before!