[Simonshall]

Hi everybody.

Disclaimer: I'm not a chemist or have much knowledge of chemistry, so please bear with me.

I very much hope you can help me clarify the following as I am looking for:

- two or more chemicals that create a "freeze" effect when reacting with each other or with water.
- "Freese" effect of about minus 10-30 degrees celsius. 
- as small an amount of chemicals as possible with the greatest possible effect

I hope this makes sense and that your clever heads can help.

Thank you in advance!

[Borek]

Mixtures based on calcium chloride hexahydrate are commonly used - but they require ice to start with.

https://edu.rsc.org/resources/cooling-mixtures/2260.article

I am afraid you might be out of luck here, while there are definitely spontaneous endothermic reactions they are not as "strong" as you suggest you need. Spontaneity in most cases comes with exothermicity (that is: reaction that are spontaneous and occur on their self just because things are mixed typically produce heat, not absorb it).