To keep your Linen Bonnets, or anything else made of linen, as good as new:
Wash linens separately from anything else, particularly items that contain polyester. Polyester “pills” and will shed its pilling on natural fibers lowering the smoothness and softness of the fabric. Select a gentle laundry detergent. Products with whiteners are not recommended on coloured linens as they may progressively fade the colours.
Launder linen products in warm water and gentle detergent. It is very important that you do not use fabric softener as it will decrease the absorbancy of the fabric so your babes head won't be perfectly temperated anymore, because sweat should be absorbed. Over time, the softener builds up on the surface of the fabric and will not be completely removed during the regular rinse cycle.
Line drying any linen is by far the best for it and the environment. It will be crumpled after washing, so the washed and easily wringed out fabric should be properly hanged. As linen is drying very well, it is very important not to let it dry too much because it will be hard to iron it.
The best way to iron linen products when they still a little bit damp: first of all it will be easier to iron and no additional dampness will be needed.
Don't mix dark and light colors. That's it, have fun!