When I got this iron, I couldn't figure out how to work it, so I actually read the instruction book. I read a couple of things that really surprised me. This is one of the them:
Do not use descaling agents, as these damage the lining of the steam chamber and so may impair the steam function.
and this is another.
Spray starch onto the reverse side of the fabric to be ironed. This will avoid your soleplate from turning brown.
The latter tip may depend on the type of soleplate your iron has. I am going to have to remember that. I use a lot of spray starch when quilting.