4 Developing Heart
A flexible model to demonstrate the early development of the heart.
Made from several colours of knit fabric. The background grid in the pattern photo is 100mm x 100mm. Also prepare two long, oversized plastic bags. These should be able to be well sealed once filled. Double-bagging is a good idea.
The flexible filling is “Floam”. Floam is made from “Slime”, with added grated polystyrene. Slime recipes are readily available on the internet on kids make-it sites e.g. http://chemistry.about.com/cs/howtos/ht/slime.htm. For this model we used the following recipe:
- Make a 6 – 8% solution of Polyvinyl Alcohol (e.g. Sigma P8136, average molecular weight 30,000 to 70,000, H2O soluble) – tapwater fine, takes a while to dissolve (at least overnight) and can be sped up with a little heat
- Make a similar volume of a 2 – 4% solution of Sodium tetraborate decahydrate – warm tapwater works well
- Stir the PVA slowly into the borax – a clear gel (Slime) will polymerise
- Pour off any excess water and knead the slime into a blob
- Prepare a similar volume of small polystyrene balls (working inside a big plastic bag, grate a polystyrene container into small pieces) and knead into the slime – this is now Floam
Once the Floam is inside the sealed bag it will keep fairly well but may dry up over a few years and need to be replaced.
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