How to unshrink a wool jumper
A wool jumper that has shrunk is impossible to unshrink once the fibres have felted. Where the garment is out of shape, a dip in water at 30C to 40C and gentle massaging by hand normally returns its shape.
Why a wool jumper shrinks
Wool is a protein fibre with a natural scale structure. The Woolmark Company explains that the cuticle, the fibre's outer shell, is a protective layer made from overlapping scales stacked like roof shingles. When untreated wool is exposed to heat and moisture the scales lift, and with mechanical agitation they start to lock onto the scales of other fibres in a ratchet-like mechanism. The scales point towards the tip of the fibre, and the Australian Wool Education Trust course material at the University of New England notes that this interlocking ratchet-like action makes the fibres travel root-first.
According to The Woolmark Company, the process leads to fibre entanglement, fabric densification or garment shrinkage. The Australian Wool Education Trust material identifies two further stages. Relaxation shrinkage happens when stresses imposed during processing relax in water without agitation. Common to all fibre types, this first stage is non-reversible. Consolidation shrinkage is a further, non-reversible stage caused by gentle agitation in addition to soaking, and in knitted fabrics it can occur with each washing.
Shrunk, or felted
The distinction matters because one condition allows for some recovery and the other does not. According to The Woolmark Company, the felting process is irreversible. Australian Wool Education Trust material describes felting shrinkage as occurring when untreated wool is treated in water with detergent and some mechanical action is applied. Fibres then migrate and mat together, giving an irreversible shrinkage.
A felted knit looks different. The fabric is denser and matted, and the stitch pattern has closed up. Woolmark notes that the exception where recovery of shape is not possible is a jumper labelled Dry Clean Only or Hand Wash that has inadvertently been washed in a washing machine and has severely felted. A garment that is merely out of shape, with shoulder humps from drying or storing on a hanger, is a different problem and can be reworked. To prevent felting, The Woolmark Company advises washing wool on the machine's wool setting, usually gentle action at 40C, or on a cold wash or delicates cycle where there is no wool cycle. Machine washable and Total Easy Care wool is treated with a polymer that masks the scale edges responsible for felting.
The reshaping method Woolmark publishes
The Woolmark Company gives a method for out-of-shape portions of a jumper, such as shoulder humps from drying or storing on a hanger. Dip those areas in water of 30C to 40C and massage them gently by hand. Woolmark gives no soak duration for this method and names no additive. The jumper normally reverts to its normal shape after drying.
Hand washing runs between 30C and a maximum of 40C, on The Woolmark Company's own instruction, with no rubbing, pulling or wringing out. Rinse well, press the water out, and do not leave the garment lying wet. For drying, place the garment on a pale or white lint-free towel, gently knead the towel by hand into shape and size, and remove as many creases and folds as possible. Hanging a wet jumper on a hanger stretches it in length and can create humps on the shoulders. Wire hangers are particularly bad for this. Line drying or drying on hangers stretches knitted garments because of the weight of the moisture the garment holds, so the garment grows in length and loses its shape. The full care routine is set out in our guide to washing a wool or merino jumper.
What we tell customers in the shop
We give care advice at both our Melbourne shops, in the CBD and in Ripponlea. Our experience is that a knitwear garment not cared for properly can lose its softness, shrink and lose its shape. The advice we give at the counter is to follow the care instructions on the garment and wash gently. The shop's other wool garments are gathered in the Wool Knitwear collection.
Common questions
Can you permanently unshrink wool?
Felting shrinkage is irreversible, per The Woolmark Company. Australian Wool Education Trust course material at the University of New England identifies relaxation shrinkage, consolidation shrinkage and felting shrinkage, describing all three as non-reversible. For a wool jumper that has lost shape but is not felted, The Woolmark Company publishes a method of dipping in 30C to 40C water, gentle hand massage, and flat drying to restore shape.
Does hair conditioner unshrink wool?
No wool authority publishes a method using hair conditioner to unshrink wool. The Woolmark Company publishes no claim about conditioner, baby shampoo or vinegar for reshaping or reversing shrinkage. The only reshaping method published by The Woolmark Company for a jumper that is out of shape, not felted, involves water at 30C to 40C and gentle hand massage.
Can felted wool be reversed?
Felted wool cannot be reversed. The Woolmark Company states felting is irreversible. Australian Wool Education Trust course material at the University of New England lists felting shrinkage as one of three non-reversible shrinkage types, alongside relaxation shrinkage and consolidation shrinkage. Once wool fibres have matted and locked together through felting, the change is permanent.
How do you reshape a wool jumper that has lost its shape?
The Woolmark Company publishes a method: dip the jumper in water at 30C to 40C and massage it gently by hand. Then lay it flat on a pale lint-free towel, knead it by hand into shape and size, and leave it to dry flat. Hanging a wet jumper stretches it in length and risks humps on the shoulders. No soak duration or additive is specified.