We have all provided pre-mixed corn starch and water goop. Next time let the children mix and experiment with the items themselves.
Understanding that combining the materials and watching the transformation is the most intriguing aspect of the early childhood sensory experience.
Provide the children with a large art tray. On the tray have a small container for mixing, a bowl with spoon of corn starch, watercolors with droppers.
Have the children scoop their own corn starch into their clear cup.
Once they have the amount of corn starch that they want allow them to drip color water into their cups.
As they drip and mix their mixture they will discover on their own how much of each ingredient they need.
When you provide your children with these types of activities the knowledge they gain is endless. Not to mention all the new vocabulary that they will be gaining.