The interaction between a primer and a foundation largely depends on their respective formulations. Let's take the One Size primer as an example. Although the exact formulation is proprietary, like most primers, it is designed to create a smooth, even base for foundation application, helping to enhance the longevity and appearance of makeup.

The key to understanding how a primer interacts with different foundations lies in the principle of "like attracts like." This means that oil-based primers work best with oil-based foundations, while water-based primers are compatible with water-based foundations.

One Size primer, like many others, is likely a silicone-based primer. Silicone-based primers are known for their ability to fill in pores and fine lines, creating a smooth canvas for foundation. They are compatible with most types of foundations, including silicone-based, water-based, and oil-based ones, due to their unique molecular structure.

Silicones have a unique fluidity that allows them to form a flexible film on the skin, which can help to prevent the foundation from settling into pores and fine lines. This film also provides a barrier that can help to prevent oil from the skin from breaking down the foundation, which can enhance the longevity of the makeup.

However, the reaction between the primer and the foundation also depends on other factors, such as the pH level of the products, the presence of other ingredients like humectants, emollients, and preservatives, and the physical properties of the foundation such as its viscosity and particle size.

Therefore, while a primer like One Size can enhance the performance of many different foundations, the exact reaction will vary depending on the specific formulation of the foundation. It's always a good idea to do a patch test or a wear test to see how a particular primer and foundation combination works on your skin.