There can be 2 questions to this answer:
Baking Powder is mainly composed of NaHCO3
When a substance which is acidic or basic in nature is dissolved in water it shows disassociation, it divides into ions. For instance HCl divides into H+ and Cl- ions. This dissociation decides the nature of a substance more concentration of H+ more is the acidity. But this disassociation of a acidic or basic substance only only takes place in water hence until and unless the baking powder is put into water it won't turn red litmus blue.
Another cause can be that you might be testing acidity or basic nature long time after putting the baking soda in water. Baking powder is not only NaHCO3 but has acidic crystals with it. So when we put in water a neutralization reaction takes place producing CO2 and H2O. After some time the basic nature could go away due to the neutralization reaction.
When magnesium oxide is tested with red litmus paper, there will be no observable change because magnesium oxide is a neutral substance. It does not exhibit any acidic or basic properties that would cause a color change in the red litmus paper.
litmus paper turns blue litmus red when tested on an acid and red litmus blue when tested on a base
Litmus paper is typically blue. If water is tested with blue litmus paper and it turns red, it indicates that the water is acidic. However, if there is no color change, the water is neutral.
universal indicator or litmus paper
The color of litmus paper turns red when it comes in contact with an acidic solution, and blue when it comes in contact with a basic solution. The color change of litmus paper can help determine the pH level of the substance being tested.
The litmus paper remain unchanged in a neutral solution.
Water provides H+/ OH- ions for the dry gas(to be tested with litmus) to show its acidic/alkaline nature.
Usually the ph is tested with a phenol red indicator but litmus paper can be used
I would recommend both Baking Powder and Cinnamon, because it depends on which surface you will be lifting the prints from. For my science project, I tested 7 common household powders. These are Cinnamon, Baking Powder, Maybelline Mineral Powder, Baby Powder, Coco Powder, Horse Radish and Cornstarch. I then compared all these prints to a "Master Copy" that was made using a professional black forensic powder. I also tested over 5 different surfaces. Including black tile, white Formica countertop, glass, aluminum can and plastic bottle. Aluminum can defiantly generated the most identifiable features followed by the plastic bottle.Cinnamon was the most effective powder (this was measured by the total number of features.)But, Cinnamon did extremely well on the plastic bottle and the aluminum can. It didn't do well on the glass, black tile or white Formica countertop. Baking powder received the most rounded results. It did well on four surfaces, while Cinnamon did extremely well on two surfaces.So, it really depends on the surface which powder you should use. So I recommend both Baking Powder and Cinnamon.
If the vinegar is strong enough to be below 4.5 pH the litmus paper will turn (or stay) red.
The acidity or alkalinity of a solution, pH indicator.
Litmus paper is another name for pH paper. They are synonymous in name and function.