Hand-brewing filter cups come in various materials like plastic, ceramic, metal, and glass. During the brewing process, these cups tend to lose heat at the point where air and water meet, leading to energy loss.

Before you start brewing, it's crucial to ensure that your brewing equipment doesn't interfere with the coffee extraction process. Preheating your filter cup can significantly impact the brewing temperature.

Let's explore the differences between filter cups made of these different materials:

Plastic:

Plastic conical filter cups are crafted from various polymers, such as methacrylates (commonly known as plexiglass and acrylic) and high-density polyethylene. Plastic has a high specific heat capacity, meaning it can absorb a considerable amount of heat. However, due to its lightweight nature, plastic doesn't retain heat effectively, making it a highly insulating material.

Ceramic:

Ceramic filter cups are favored by many baristas for their insulation properties and appealing aesthetics. Compared to plastic, ceramic has a lower specific heat capacity per kilogram.

While this makes it a more stable material, ceramic filter cups are several times heavier than plastic ones, resulting in the absorption of significantly more heat from the brewing water. Therefore, preheating a ceramic filter cup is essential to maintain temperature.

Glass:

Glass is an excellent material for brewing tools. It's easy to clean, possesses a relatively low specific heat capacity, and is almost half as heavy as ceramic. Due to its weight, glass filter cups do not absorb as much heat.

Metal:

Metal filter cups have a very low specific heat, making them a favorable material for brewing. However, they are efficient heat conductors, meaning they rapidly absorb energy from the brewing water and release heat into the surroundings.

Metals can be manufactured very thin, reducing their weight and heat absorption. Filter cups made of metal result in a quicker temperature drop, making them more suitable for short brews.

One key aspect to consider is the insulation of the filter cup, which directly impacts the temperature during coffee extraction. A well-insulated filter cup minimizes heat loss, ensuring a consistent temperature for more reliable extraction efficiency.

Additionally, different materials have varying specific heat capacities, affecting their ability to absorb heat. Even with the same water temperature, the rate at which the water temperature changes in the filter cup varies with the material used.

Consequently, the actual temperature of the water in contact with the coffee grounds differs for filter cups made of different materials over the same time period.

The choice of filter cup material impacts heat retention, weight, and heat absorption during the brewing process. Understanding these material differences can lead to better control over your brewing temperature.