I made this flexible geometry toy based on one I saw in a learning store. You can bend it into different shapes, and it's fun.

Unfortunately, all I had on hand was some yarn to make the inside support.

I'm concerned that the yarn is eventually going to snap, or the knot is going to unravel. It's also not water-proof, so it might not be that great for extended kid use due to the messes they make.

What can I use instead?

I'd like something that:

  • Is strong, so it doesn't snap
  • Has some flex, so the toy can bend like it's supposed to
  • Is somewhat waterproof
  • Can easily be knotted in a way that won't unravel
  • Be able to have at least 3 strands of it threaded through a 4mm wide straw

Here's the toy, to give you an idea of my requirements:

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  • I'm puzzled: why is yarn not waterproof? Don't you wash your sweaters?
    – Martha
    Jul 12, 2016 at 4:11
  • @Martha I can't wash the toy, easily, or tell when it needs washed if baby slopper or food gets down into the straws. Waterproof material would let me just rinse it off every now and then.
    – user24
    Jul 12, 2016 at 4:12
  • What I'm saying is that I don't see why you can't "just rinse it off every now and then" if you used yarn. Are you concerned about drying time? Why?
    – Martha
    Jul 12, 2016 at 4:15
  • @Martha Because if it gets wet and I don't know it... it'll get musty and mildewy. Then I'll have to try and wash it and scrub between the straws, hoping I don't fray it. And some of the yarn is fraying already :/
    – user24
    Jul 12, 2016 at 4:26
  • If this is a baby toy I'd be more concerned about young kids cutting their mouths on the sharp straw edges than I'd be concerned about the yarn stretching. And I agree with Martha, synthetic yarn washes well and dries quickly - I recommend nylon for strength, stretch, and washability. You can also buy small denier (long and thin like yarn) elastic by the yard in craft and fabric stores. With kids, no matter what the toy is made of, you should wash toys frequently - just slosh them around in soapy water and rinse and let dry.
    – user1798
    Jul 6, 2017 at 23:54

6 Answers 6


Instead of yarn or thread, would fishing line work for you?

  1. Different strengths available.
  2. Is flexible.
  3. Is made to be in water.
  4. Can be knotted.
  5. Variety of diameters available.
  • I thought about this, but I've not had good success with getting it to knot. Is there a better way to secure the knot than just hoping for the best? Does a glue work? Can you fuse it with heat?
    – user24
    Jul 10, 2016 at 20:03
  • Some finishing lines can be melted. youtube.com/watch?v=cONydFcpYtk Jul 10, 2016 at 20:08
  • 1
    It'd be very helpful if you could include a rundown of that process in your answer, if you know how to do it!
    – user24
    Jul 10, 2016 at 20:17
  • With fishing line, I'd be concerned about it cutting into the plastic straws.
    – Martha
    Jul 12, 2016 at 4:17
  • If you can find/use braided fishing line, (as available in the USA but not so much in Europe) it will be easier to tie than monofilament. It is also a bit less sharp so less likely to cut into the straws.
    – Willeke
    Dec 23, 2016 at 19:29

A lil drop of superglue on the knot will lock it down, the liquid kind, not a gel. It wicks into the fibers. Superglue, or any cyanoacrylate-based glue works great on fishing line as well.

Maybe try mason'-s line at a hardware store. It's the string they stretch and place a hanging level on. It usually comes in hot pink or other bright colors.

  • I like the idea of fluorescent colors. That's fun!
    – user24
    Jul 10, 2016 at 22:05

Baker's twine String from the baker, the kind they wrap around the box.

  • 1
    Also available in cook shops as they use it to tie meat before putting it in the oven. And now also craft shops, as people found it nice to work with because of the colours.
    – Willeke
    Dec 23, 2016 at 19:33
  • Recently watched an episode of Kawaii International and they demonstrated making a Himmeli ornament. They used vinyl covered wire with straws. Kawaii International is a program given by NHK World. Mar 25, 2019 at 22:18

You could also use beading wire, like SoftFlex. It is designed to be knotted and has a nylon coating that will protect it from moisture.

However @martha is correct that you will have issues with the line cutting through the straws.

Very thin paracord might work, but you may still have issues with mustiness.

And regarding securing your knots...there is a knot called the fisherman's knot for a reason. Fishing cord can be super slick. Check this out for instructions. (I just noticed that you asked the question that I linked to, so maybe the fishermans knot didn't actually work for you. Sorry about that).

There are also a lot of great tutorials about knot tying on-line, and they will often break the different knot types down by usage. Look for knots specifically used for fishing, and you should find some good knots for securing fishing line.


A good alternative would be Dental floss.


It looks like nylon cord could be used. If more flex is desirable then a braided rubber cord. Some rubber is of poor quality, becoming brittle after a few years and breaking easily.

  • Do you have examples or anything to spruce up your answer? Are there certain types of nylon cord that work better? How about the knotting or fusing the ends, any tips? Feel free to edit with some more info if you can! Thanks!
    – user24
    Jul 11, 2016 at 0:18

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