The naked vases of GREAT are made from liquid black clay. After baking they get a dark brown colour. From the outside they are unglazed and therefor very matt. So all of this added up; they look like they are excavated from an ancient archeologic grave.
Ofcourse the inside is glazed and 100% waterproof. And… every vase is handmade, so be patient when they are out of stock. It will take a week of 4 to make a new vase. But they are worth waiting.
Do not clean it in the dishwasher. And if the bottom outside becomes wet, dry it first upside down. Clay is a natural product when wet it can leave stains on wood.