Michael Chylinski answered:
That hat is straw, it was a floppy ladies hat, I found it in a bucket of beanies at a thrift store for 50c I took all decorations and etc off. I stiffened the fabric with diluted PVA glue. I stretched over a open crown hat block that I also made by hand. Using steam and an iron. Then I removed it from the block and with additional steam I bashed the crown shape by hand. I think I also sprayed it with shellack to give it some shine, also adds stiffness, also enriched the color of the straw. Then I made the hat band using millinery grosgrain and Renassance ribbon and I sewed in a speech terry cloth sweatband. The brim was stingy and stuff enough it didn't need a wire and I chose not to put a ribbon around the outside edge of the brim. My son loves it. I could sell it for up to $50 I'm sure. I've done the same with crochet hats, wool and fur felt, various straws. Standard hat blocking techniques and materials.