I do a lot of international pottery related traveling as a presenter or resident artist or the like. Hand tools got in chacked luggage... labeled clearly as such. Nothing pointy or what a "normal person" (not a potter) would consider wierd in carry-ons.
I ship anything questionable to the venue ahead of time via FedEx. With a full itemized invoice, CAS #s, and MSDSs included. And expect that it will get confiscated.... but it never has.
Gray plastic clay in ANY luggage is going to get a good going over (at a glance likely looks a lot like plastic explosive). Any white powder,....... ditto.
I was working with an international ceramicst once that made the mistake of packing powdered white slip in his suitcase. He ended up literally staring into a bunch of AK-47s in a country where he did not speak the language. He got thru it... but it was NOT fun for about 1 hour until they verified what the stuff was.
Returuing to the US from Japan one year I once had some nice knives (Japanese knives are the BEST) and a carpenter's saw in my CHECKED luggage. The US TSA has a group in the Narita Airport for returning to US flights........ long story short.... I soon had my checked bags unpacked and spread out all over the floor at Narita as they went thru every single bit of it.
Err on the side of caution. See your airline's policy site. Check the country you are flying into for regs on import/export.