A Fosshape® base is a solid foundation for a hat or fascinator shape which can be covered in a softer fabric like silk or leather.

Fosshape® is a type of thermoplastic. In hat making, it is often used as a buckram replacement because it has a similar strength to this traditional millinery foundation without the drying time.

Fosshape® comes in three densities – 300, 400, and 600 – with 300 being the thinnest and easiest to work with for millinery. It resembles a thick felt and is sold by the yard by millinery suppliers like Humboldt Haberdashery.

This useful thermoplastic doesn’t fray and is lightweight and sewable. In millinery, it is usually used as a base and covered with fabric or leather, but it can be dyed and painted on its own as well.

Fosshape® is especially useful for odd or difficult hat shapes. A handheld steamer with a flat plate is the best thing to use to heat this fabric. Because it will not fray and sticks to itself, you can cut out the bulky areas, overlap the seams and seal with steam and pressure. You should always be really careful not to burn yourself when heating thermoplastics, though. Wearing heat-proof gloves is highly recommended!

My favorite thing about this thermoplastic is that it requires no water, stiffener or drying time, so using it greatly reduces the labor and time needed to block a hat base. This tutorial explains the basic technique for blocking Fosshape®. You can adapt these instructions to work with any shape or size hat block.

This Fosshape® Hat Base Project was written by Amy Fowler.

Category: Fascinators, Hats, Hints and Tips

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