To keep your linen bonnets, or anything else made of linen, as good as new:

Wash linen separately from everything else, especially from items containing polyester.  Polyester "pills" and loses its pilling on natural fibres, which reduces the softness and suppleness of the fabric. Choose a mild detergent.  Products with bleaches are not recommended for coloured laundry as they can gradually fade the colours.

Wash laundry products in warm water and a gentle detergent. It is very important not to use fabric softener as it reduces the absorbency of the fabric, so that your baby's head is no longer at the perfect temperature, as sweat should be absorbed. Over time, the fabric softener settles on the surface of the fabric and is not completely removed during the regular rinsing cycle.

Drying your laundry on the clothesline is by far the best for the laundry and the environment. After washing, it will crease, so the washed and easily creased fabric should be hung up properly. As linen dries very well, it is very important not to let it dry too much as it is then difficult to iron.

The best way to iron laundry products when they are still slightly damp: First of all, it will be easier to iron and no extra moisture is needed.
Do not mix dark and light colours. That's it, have fun!