Fosshape® for Hat Making

There are many thermoplastics that have interesting applications in millinery, but one of the most useful is Fosshape®.

Fosshape® has been referred to as a buckram replacement, as it has a similar strength to buckram without the drying time. It resembles a thick felt and is sold by the yard by millinery suppliers like Humboldt Haberdashery.

The Benefits of Fosshape®

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® comes in three densities – 300, 400, and 600 – with 300 being the thinnest and easiest to work with for millinery.

hat brim edge with millinery wire

A handheld steamer with a flat plate is the best thing to use to heat this fabric. 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.

Blocking with Fosshape®

Fosshape® is especially useful for odd or difficult hat block shapes. 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.

As always, you will want to protect your hat block before you begin. Because you will be applying a higher amount of heat directly to the block, it is better to use aluminum foil or a Teflon freezer bag to cover your block to avoid any potential melting issues.

Fosshape® for hat making

Use the N-S-E-W process to start blocking, then work the quarters in between. If you have tight curves, instead of pulling the pleats out, gather them into a single large pleat and trim the excess back, leaving enough to make an overlapped edge. These overlap spots will flatten out with a little extra pressure.

The most important thing to remember when working with Fosshape® is that it shrinks 15 – 30% when heated. To account for this, you will need to leave a longer selvedge edge when trimming back the excess.

You do not want to stretch the fabric tightly around the block like you would when blocking with a traditional millinery material. Instead, pull just enough to hold the fabric flat against the block and secure with pins. If you do stretch the fabric too tightly and a hole forms while steaming, don’t worry! You can use a small scrap of Fosshape® to cover and seal the hole.

Fosshape® for hat making

As you steam the Fosshape®, it will retract and stiffen into more of a soft plastic shell. Move the steam a few inches away from the material to start the stiffening process then go back with some pressure to firm the material up further, especially on any overlaps or patches. Be really careful not to burn yourself when heating thermoplastics. Wearing heat-proof gloves is highly recommended!

Feel all around the piece for any fuzzy or soft areas – those are areas that were not heated enough to stiffen. After stiffening, pull out the pins and press those areas well.

Fosshape® for hat making

Before removing the hat base from the block, cut away excess material (leaving just a couple of centimeters to work with). A straight edge knife is the easiest tool for doing this with. If you have a more complicated block shape, you may have to cut the material. Any cuts can be patched with another scrap of the thermoplastic.

Fosshape® for hat making

Once your Fosshape® hat base is trimmed and removed from the block, you can work with it just like you would a traditional buckram base. And the best part is, you created it in a fraction of the time!

Thermoplastics Projects

Click HERE for all Thermoplastics Projects.