A dual-chamber package for the constituent materials for preparing an alginate dental impression paste includes a first chamber containing a pre-measured volume of water, and a second chamber, attached to and isolated from, the first chamber, and containing a pre-measured quantity of alginate powder, wherein the quantity of powder and the volume of water are in a pre-determined ratio for making a dental impression paste when mixed together. The powder and the water may be mixed outside of the package by dispensing the water and the powder respectively from the first and second chambers. Alternatively, the powder and water may be mixed within the second chamber by breaching a barrier between the first and second chambers to allow water to flow from the first chamber into the second chamber, after which the alginate dental impression paste is dispensed from the second chamber.