When combined with a
な-Adjective,
にする (or
くする in the case of
い-Adjectives) carries the meaning of ‘to make more (A)’.
Just like the
にする grammar point that is used for highlighting decisions, this
にする construction implies that the speaker has a high level of control over the action.
-
この建物（たてもの）をもっと丈夫（じょうぶ）にする方法（ほうほう）がありますか？
Is there any way to make this building more durable?
-
汚（きたな）い部屋（へや）を綺麗（きれい）にするのは大変（たいへん）だ。
It is difficult to make a dirty room clean.
-
風呂（ふろ）を熱（あつ）くするよ。いい？
I'm going to make the bath hot. Is that okay?
-
このコーヒーを甘（あま）くするために、砂糖（さとう）をください。
Please give me sugar to make this coffee more sweet.
Basically, this changes the adjective into an adverb, and then uses
する to show that the adjective itself is the thing that is being done.
にする is one of four regularly repeating grammar patterns in Japanese that highlight the level of control that the speaker has over the action/result of an action. From highest to lowest level of control, these are as follows:
にする - High level of control, the speaker/subject can perform this action themselves.
になる - High level of control, the speaker/subject can perform this action themselves, but there is no external target.
とする - Medium level of control, the speaker/subject can perform this action, but some outside factors may need to be considered (difficulty, other people, time, etc.).
となる - Low level of control, the speaker/subject has almost no control over these actions, and something that came about purely due to external factors is being discussed.