Single-Acting Fast Acting: reacts immediate when combined with water and carbon dioxide expands during heating. In the past this was generally a cream of tartar-sodium bicarbonate or a calcium monophosphate-sodium bicarbonate mixture. Because it reacts immediately, most homemakers do not have the skills to use it.

Intermediate Between Double Acting and Single Acting:reacts rapidly when liquid is begun to be heated. Generally, the manufacturer will adjust the solubility to make this a fast acting baking powder once heated. They do this by affecting the solubility.

Double Acting: reacts when liquid is added and also reacts upon heating.

Review Questions What type of acid salt does one choose for a baking powder? Why?

There are other chemical leavening agents. Ammonia bicarbonate is used in quick-cooking, thin products that does not allow for ammonia buildup. It is used in the original "high quality" sugar cookies as it is less likely to leave residue and the pH is generally lower. The pale sugar cookie is the standard.