Using litmus indicator paper

 

I think litmus indicator paper is a nuisance because you need two bits of paper to tell whether a substance is acid, alkali or neutral. In my photo, the top paper of each paper started red each time and the bottom paper started blue. 

A substance is an acid if red litmus STAYS red and blue litmus TURNS red.

A substance is an alkali if red litmus TURNS blue and blue litmus STAYS blue.

A neutral substance, safe like water makes red litmus stay red and blue litmus stay blue.

Ahn odd thing was the toothpaste. I was taught that toothpaste was a very weak alkali. It looks neutral here. A brief bit of Internet research suggests that toothpaste can range from very weak acid, through neutral to very weak alkali. It depends on what you buy.