Nitram Liquid Charcoal 50ml Tube

It's amazing product, can be used in multiple ways, traditional rendering or diluted with water used like water color, creates beautiful layers, endless tonal values
No dust and stays put without fixative
Can be used with paper, canvas or canvas boards
It's great

Great product - using with mixed media for landscape work - very effective.
However the 2 tubes I have bought have blocked up and I've been unable to use over half a tube's worth. It's not a cheap product so want to use to full extent.
Any tips on keeping the contents pliable gratefully received.

The only product ever bought from KB that I have been very disappointed with. The description says it has the consistency of oil paint, but the tube I received was very runny - initially it looked like the gum arabic binder had separated, as sometimes happens with watercolour, but I squeezed out a fair amount and it was all very runny. Disappointing, as I had read excellent reviews and was looking forward to trying it. (Also noticed on the back of the tube a warning that it contains chemicals known to cause cancer - probably wouldn’t have bought it if I’d known this earlier, although I might have just missed it in the product description.