Getting Slimy

I think we’re going to hit the 1000 bags of slime target tomorrow. There is an event on campus for 10 year olds, and we’re expecting a fair number. I’ve not been keeping precise count of the numbers we’ve reached, I’ve been back calculating by how far through the stash of 1000 lolly sticks, 1000 plastic bags and 1000 plastic cups I am. I can confirm that I’ve ordered more of all three items.  We started in June last year, and between us (me, and several very willing volunteers), we’ve done quite a bit!

I like PVA slime as an activity because it is tailorable to all age groups and you can relate it to a fair number of concepts of interest depending on the people standing by you. I’m slightly less keen on brewing up the PVA solution – 4% w/w in hot tap water, 3.5 L at a time to be diluted to 5 L. It takes me about 2 hour to get it all dissolved and that’s assuming I do things the sensible way rather than lobbing all the PVA in and hoping for the best.  That’s probably around 25 litres of PVA solution so that’s quite some time!

We usually combine it with making worms from sodium alginate, cross-linking with calcium chloride. Again, it’s a good activity for a range of ages and if  you challenge the group to see who can make the longest worm (not easy in a small cup or beaker of calcium chloride), it get’s quite entertaining. We had some feedback from the Spooktacular Hallow’een event last year that slime was more appealing because you could take the product home in a wee bag, whereas the worms (which don’t really last) were disposed of fairly quickly.

If you think I resent brewing up the PVA, alginate is horrific! No hot tap water allowed so by the time I’ve heated the DI water, and carefully sprinkled in the alginate powder, spent a couple of hours stirring (in addition to the magnetic stirrer), chopping any lumps, burning my self with hot sticky stuff, and filtering it into bottles through a funnel to catch the lumps, I’m usually somewhat fraught. Then there’s the curious mystery of why the red food dye version always decolourises if left for any length of time. Never the yellow, green or blue, just the red one.

Anyway, 10 year olds tomorrow, and perhaps a significantly slimy milestone!

One thought on “Getting Slimy

  1. I’d love to know about the red dye! We use electrical insulation tape for a variety of marking purposes, and sometimes leave tags made of it in the field, and the red one loses colour where none of the others do (actually this can be an advantage because when red it is much more likely to be eaten by sheep and deer and perhaps other herbivores, but still…) – maybe there’s a connection?

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