Water Temperature Controlling with Arduino

Hi, i have a couple of questions. 1-)I want to control temperature of water which has a constant volume with 220VAC current and a heating element precisely (error should be betweeen 0.1-0.3 degree celsius). But i can't decided what should i use for controlling AC power. There are many many options like solid state relay, mosfet, triac etc. As far as i understand these options provides on/off control. I want to use PID control too. Are there any other options for regulating AC power continously (not on/off like regulating current)?

2-)In addition, temperature range will be between room temperature and 45 celsius. So the heating element and 220VAC maybe too powerfull for this project. Do you have any other suggestions for heating? (Actually i prefer less power and DC current for portability and security)

NOTE: Heating time is important. I have not much knowledge about electronics so please explain simply. Thank you for your answers.

okan26south: and 220VAC maybe too powerfull for this project.

NOTE: Heating time is important.

These seem to be conflicting statements. 220v is not a definition of power, and you don't talk about watts, which is, but, since heating time is important, delivering the power with a 220v element is likely to be a good idea.

The other thing you don't talk about that would have a vital bearing on the job is the actual volume of water.

The arduino bit should be dead easy. The only thing you need to consider there is whether you actually need one.

You are right powerful statement was wrong. Sorry about that. Volume of water will be nearly 1 liter and setpoint temperature will be variable.

Do not double post.

45C.... C41 colour film express processing?

There must be tons of used heating / temperature control equipment around from pre-digital days.

Do not double post.

As member okan26south is discovering, a triple post is a perfect way of earning a forum time-out.