When people say 30 parts water to 1 part CMC, is that like 1tsp CMC 30tsp water?  

Yes.

But a little goes a long way.

I'd do a half a teaspoon of water and a couple of tablespoons of water...  thinking about it (I just judge by eye) I reckon you may need more water...  See how it is after a couple of hours and it's all dissolved.

You mean 1/2 tsp CMC 2 tsp water? So you have to leave it a hour or 2 to thicken before you use it? Thank you :)

I put a sprinkle between my fingers in a small container - I use hard plastic covers that used to be on my kids' dummies, (so small), and put a little stream of water over it. It doesn't need to be an exact ratio. You can use it immediately, but the CMC probably takes 10 minutes or so to dissolve really well. A little really does go a long way. I've never done a cake whee I've needed to use more that a tiny pinch of powder.

I've got loads of CMC so I'm not to worried about wastage. Just wanted to double check that what I'd read 1/30 was correct. Thank you :)

Just remember when you are making it in BULK quantities like you are suggesting that it is wise to pour a little out into a small container to use - discard after use

Dipping your brush into your large container is just going to introduce bacteria and it will go off really quickly

Thanks, I just need it for an hour to attach decs to my mums birthday cake. Who knows when I'll be doing that again so will bin it when I'm done.

Thanks again :)

Another trick  for just a little glue is to put a pea sized ball of gumpaste into a new - empty nail polish bottle - fill the bottle with warm water and let set over night.  In the morning you'll have just enough for your project.  If you have nothing to do while watching TV you can shake the container to dissolve the gumpaste quickly.

If you mix the cmc with vodka instead of water it kills bateria every time you put your brush into it.