Welcome to ModelEngineMaker !If you have problems registering or logging in, please use the contact menu option to request assistance.
I do need some for sand casting and it is EXTREMELY expensive where I am (Ontario Canada near Toronto). One quote was $1000 for a 40 kg bag.
The $1000 quote is not a typo and was from a foundry supply firm (not Smelko).
Awake - if the lumps in the used stuff are same size you need for your cores, nope, no problem. Might be some odd odours from the foundry.....