Thursday, July 19, 2012

Silly Putty Proportions

This silly putty recipe made a gigantic amount of silly putty and took 2 adults a good 30 minutes to knead (with a little help from J).  Ultimately, it split up into quite a few different little hands (who weren't around to help knead it).

This large silly putty blob was made from 2 cups white Elmer's glue and 1 cup liquid starch (StaFlo) (J was in charge of the food color, so I'm not sure how much actually made it in the batch):

Massive amount of silly putty

I wanted to experiment since that's what scientists do best (and I wasn't 100% satisfied with try # 1).  I wanted to get the optimal proportion for each kid at the preschool I'm visiting on Friday (mainly to be organized) and make sure the experiment could be replicated and the questions I ask will be able to be answered.

So, I varied the glue/starch ratio to see what happens.  I started with 1:1 since I found a site that said it works that way.  FALSE.  It was just a gooey mess, so I added more glue to get it 1.5:1 (white).  I kept the other at 2:1 (blue).

The white putty had 3/16 of a cup (1/8+ half of 1/8) of glue and 1/8 cup of liquid starch.  The blue had one drop of blue food coloring, 1/4 cup white glue, and 1/8 cup liquid starch.  Both fit nicely into zipped sandwich baggies.

My opinion of the two:

I'll stick with the 2 parts glue to 1 part liquid starch (the original recipe).  Mixing it in a smaller batch allowed less kneading and it absorbed the liquid starch much better than a bigger batch.  Thus, it's not as gooey or stretchy as the previous batch.  It actually feels more like silly putty.

The 1.5 part glue to 1 part liquid starch made the putty come out almost the texture of egg whites (and I'm guessing having it white color didn't help me with that association).

Anyways, I'm excited to be bringing science to the kids tomorrow.

Main points to Friday's lesson:
*Intro to chemistry - you have two (or more) different parts, and when you mix them together, you create something new.
*Intro to material science - some materials behave differently when pulled at different rates (under different loading conditions, ie. soft gentle pull versus a fast tug).
*Have messy fun.

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