Start offering solid food to baby kittens at around four weeks. As with most species, mother knows best, and cats are no different. Mother cats will start the weaning process by nudging baby kittens away at about four weeks of age, so feel free to step in and offer the kittens tasty kibble at about the same time.
http://pets.thenest.com/kittens-ready-eat-solid-food-7559.html
The answer to the question of when can kittens be weaned is about 10% technical and 90% common sense. If you just let nature take its course, chances are that your newborn cats will adjust and grow into happy, healthy cats.
http://www.petyak.com/cats/kittens/articles/when-can-kittens-be-weaned/
The process of weaning usually starts when kittens are about three to four weeks old, and takes two to three weeks to complete. If you are bottle-feeding an orphaned kitten, or one whose mother isn't able to feed her, weaning can begin as early as three weeks.
https://www.petcentric.com/05-30-2016/when-to-wean-a-kitten/
Weaning is a big step in a kitten's young life. It happens when kittens move from mother's milk to solid food. Just as important, it's a time when a kitten moves from depending on her mother's care to becoming a more socially independent cat.
https://www.petcentric.com/05-30-2016/when-to-wean-a-kitten/
That’s normal. At eight weeks of age or older, it is highly unlikely that a mother cat will still allow a kitten to feed at all. If the young cat still refuses to eat solid foods after 10 weeks, take her to the vet as soon as possible. Kittens need to eat regularly in order to survive at that tender age.
http://www.petyak.com/cats/kittens/articles/when-can-kittens-be-weaned/
By the time the kittens are 8 to 12 weeks of age, they should be eating solid food and no longer nursing. For most kittens, separation from the mother should be delayed until the kittens are 12 weeks of age, to allow normal socialization and bonding.
http://www.petplace.com/article/cats/keeping-your-cat-healthy/kitten-care/weaning-kittens
During this time, allow the mother to stay away from the babies for longer periods of time. For some mothers, you may have to be persistent. Some mothers and some babies may not wean properly. Mothers that do not begin to push away their kittens by 4 weeks of age will need help. Weaning should progress slowly, to reduce the incidence of anxiety and mammary gland inflammation in the mother.
http://www.petplace.com/article/cats/keeping-your-cat-healthy/kitten-care/weaning-kittens
If the kittens are still with their mother, mom will gradually say no! to frequent nursing sessions and tell them to find other food sources. It's for their own good - left to their own and nature’s devices, kittens no longer need mom’s nutrition at 8 to 10 weeks.
http://pets.thenest.com/kittens-ready-eat-solid-food-7559.html
The weaning process is over — congratulations! — and your kitten is ready to move on to other adventures in development, with her nutritional foundation firmly in place. Just be sure to keep feeding her kitten food during those first 12 months, since kittens continue to develop throughout their first year.
https://www.petcentric.com/05-30-2016/when-to-wean-a-kitten/
Weaning Kittens. Weaning Kittens is a fairly easy process, but must be done correctly for the health of the kittens AND their Mom. Follow these simple steps and your care of kittens will aid in good health for them. When the kittens are between 3 and 4 weeks of age, it is time to begin the process of weaning them. It is time to teach the kittens to eat from a dish. I often begin by offering milk replacer (do NOT give cow's milk to kittens) in a VERY shallow dish.
http://www.askthecatdoctor.com/weaning-kittens.html
what age do you wean kittens
Wean kittens at the age of three to four weeks. The kitten weaning process begins at about  three or four weeks of age.