Resist Felting: How a Resist Turns Flat Wool into a Hollow Shape

Every seamless felted object — every bag, bowl, hat, slipper and vessel — is made the same way. Wool is wrapped around a flat barrier so the front and back cannot join, and when the barrier comes out, what is left is hollow.

The barrier is called a resist, and understanding it is what turns wet felting from making flat sheets into making things.

The principle

Wool felts to wool. It does not felt to plastic. Lay a plastic shape down, cover it with wool on both sides so the fibres wrap around the edges, and those wrapped edges felt to each other while the two faces stay separate.

The result is a closed pocket. Cut an opening, pull the resist out, and you have a bag with no seam anywhere.

What to make one from

• Thin foam camping mat — the best general choice. Flexible, slightly grippy, cuts with scissors, survives dozens of projects.
• Bubble wrap, several layers taped together — free and perfectly good for a first attempt.
• Plastic document folders or file dividers — good for small flat shapes. Sharp corners need rounding.
• Corrugated plastic sheet — stiff, ideal for hats and anything that must keep a precise outline.
• Laminated paper — fine for small pieces such as purses.

Round every corner. A sharp corner concentrates the wool and leaves a thin, weak point that often tears when you pull the resist out.

Sizing: allow for shrinkage

The resist must be substantially larger than the finished object, because the wool shrinks around it.

• Merino, firmly fulled: allow 35 to 40%
• Corriedale or medium wool: allow 25 to 30%
• Thick, loosely felted pieces: 20 to 25%

So a finished bag 30 cm tall needs a resist around 42 cm tall in merino. Shrinkage is also directional — pieces shrink more along the direction you roll them — which is covered in wool shrinkage when felting.

Make a test piece the first time with a new wool. A 20 cm square felted the way you intend to work tells you your personal shrinkage rate, and that number is good for every project afterwards.

Wrapping it

1. Lay the first layer of wool over the resist, fibres running one way, overhanging every edge by 3 to 4 cm.
2. Second layer at right angles. Two thin layers per side is the minimum; three for a bag that must hold weight.
3. Wet and press that side with warm soapy water until it is flat and dark, with no air trapped.
4. Turn the whole thing over and fold the overhanging fibres onto the back, smoothing them flat. This wrapped edge is what becomes the seam.
5. Lay the back layers the same way, again overhanging, and fold those edges over to the front.
6. Wet, press, and check the edges. Thin spots along the fold are the commonest failure, and they are trivial to fix now with a wisp of wool.

Felting it

Rub gently through net or bubble wrap, both sides, until the surface holds together. Then roll — in a bamboo mat or a towel, 50 rolls, unwrap, turn 90 degrees, repeat. The whole process is the same as flat wet felting, only wrapped.

Two habits specific to resist work:

• Rub the edges deliberately. Fibres over a fold get less friction than the flat faces and stay weak if ignored.
• Check for the resist felting through. If wool from front and back has met around a thin patch, ease it apart early with a finger.

Cutting it out

Test first: pinch and pull. If the wool holds firmly and no fibres separate, it is ready. If it stretches apart, keep felting.

Cut the opening with sharp scissors — straight across the top for a bag, a circle for a vessel. Ease the resist out slowly; folding it helps. Then reach inside and smooth every internal surface.

Now do the most important step: keep felting with the resist out. Fulling after the opening is cut is what firms up the cut edge and makes it look intentional rather than raw.

Shaping

Once hollow, the piece can be moulded while wet — over a bowl, a hat block, a ball, a shoe last, a jar. Wet felt takes and keeps whatever shape it dries in, which is what makes bowls, hats and bags possible at all.

More than one resist

Extra resists give extra pockets. A small one inside a large one produces an internal pocket; two side by side produce mittens or slippers from one piece. It scales up as far as your patience does.