Odd question I know but planning to visit a couple of guys when travelling over the next few weeks and I have a lot of spare gunge I can bring. But I'm a bit nervous about getting gunge powder through security! Anyone else done this? Did you have any troubles?

That's a good question I haven't but it you let them know what it is and it's for an art project I think you will be ok.

I work in aviation and have some knowledge of dangerous goods regulations. As long as its not classed as a flammable substance you should be ok especially in checked luggage. Just don't pack it in a format where it can be perceived as an illegal substance especially if the powder is white (I'm being serious). Leave it in its original commercial packaging if it comes like that.

I have - but no problems.
A couple of times, when staying at conferences or hotels, I mail it to myself ahead of time.

When packing, wrap it in double plastic bags...just in case.

TSA (USA) guidelines state:

"Powder-like substances greater than 12 oz. / 350 mL must be placed in a separate bin for X-ray screening. They may require additional screening and containers may need to be opened. For your convenience, we encourage you to place non-essential powders greater than 12 oz. in checked bags."

Reading that (which was in reference to baby powder), and seeing that food seems to be allowed, I think you should be fine with gunge powder.

I assume the USA is the strictest with airport security, so I would assume you're good to go in Europe.

Cheers everyone. For anyone following this thread, I was successful in taking it from Europe to South America